It’s so nice to see your plantings turn green and bear fruit, but not always everything goes smoothly. Often some diseases appear, and in order to heal your plantings, you need to know what kind of disease has befallen you and how to properly treat the plants.

Cucumbers are a fairly common and beloved plant. They can be pickled, salted, added to salads... Therefore, they are popular in the garden beds of numerous summer residents. But in order to grow them, you need to know how to care for them, especially if the cucumbers are sick and white spots appear on the leaves of the cucumbers.

When growing this plant, vegetable growers are faced with a large number of problems, including the appearance of white spots on the leaves of cucumbers. To grow a good harvest, you need to know plant diseases and symptoms, causes, features of caring for vegetables, rules for processing cucumbers and much more. You will learn about all this in this article.

White mosaic

White spots may indicate a fungal or viral disease. For example, a disease such as white mosaic is dangerous only for plants growing in a greenhouse.

The symptom of the disease is star-shaped spots. If action is not taken in time, the entire sheet will turn white. Only occasionally will veins of natural green color be visible. An affected cucumber usually does not bear fruit.

And if the fruits do appear, they look painful: small in size with numerous tubercles. The vegetable is also colored with white and yellow stripes. We have listed the main symptoms of white mosaic. We hope this will help you in identifying this disease.

The disease has been identified. What to do next?

As soon as you notice white spots, you need to immediately destroy the plant, and not wait until it begins to bear fruit. White mosaic is a viral disease. Therefore, it is quite difficult to fight him.

You should immediately disinfect all garden tools, buckets, containers and other equipment using a five percent solution of potassium permanganate.

You should also remember that only two-year-old (maximum three-year-old) seeds are suitable for planting. They are pre-soaked in strengthening solutions.

It is also important to remember about crop rotation: the planting site needs to be changed every three years. Before planting, it is recommended to treat the soil with special mixtures.

Spider mite

Also, the appearance of white spots on cucumber leaves can be caused by spider mites. The first symptom of this disease is white spots in the form of dots. The disease causes the cucumber leaf to dry out.

Another symptom is the presence of cobwebs on the underside of the leaf. How to get rid of the pest and save the harvest?

First of all, collect the affected leaves and burn them. It is also recommended to treat the vegetable with special solutions: Fitoverm emulsion or Bitoxibacillin suspension or Karbofos or Fufanon suspension. Any weeds near the cucumbers should be removed.

Ascochyta blight

White spots on cucumber leaves appear due to infection of the plant with ascochyta blight. This disease manifests itself in the form of cracked white or brown spots on cucumber leaves. The fruit gives the impression of being cooked only. After a while, the cucumber may turn black and dry out. Ascochyta blight is an infection that affects weak vegetables. A favorable condition for the development of the disease is air humidity.

The infectious agent can remain in the soil, seeds and plant debris for a long time. If you notice the first signs of ascochyta blight, immediately spray the cucumbers with 1% Bordeaux mixture. If the plant is seriously ill, burn the cucumbers along with the roots in an area not adjacent to the summer cottage.

Powdery mildew

Another threat to your cucumbers is powdery mildew. It can be recognized by the white spots on the cucumber leaves. The disease can cover the entire surface of a leaf with a white coating in a short time. In turn, shoots and young stems suffer from this, which leads to loss of yield.

This disease is curable. The main thing is to identify the disease in time and take measures to eliminate it.

The first step is to get rid of plant debris. A special solution is prepared directly for cucumber leaves: an ampoule of topaz is diluted in a ten-liter bucket of water.

With frequent use, the pathogen may become resistant to Topaz. Then network, if the effect of using the drug weakens, then use the drug Farmayod. Its solution at the rate of 2 ml per 1 liter of water usually suppresses powdery mildew well. If you cannot find Farmayod, then to prevent the emergence of resistance, it is advisable to alternate Topaz with such biological products as Alirin-B, Baktofit. In this case, it is better to dilute the drug Alirin-B in a higher concentration - at the rate of 5 tablets / 1 liter of water

Anthracnose

It is a very dangerous fungal disease for cucumbers. Anthracnose can affect not only the leaves, but also the fruits of the plant. Infection begins with the appearance of white spots on cucumber leaves. Then they turn brown.

The leaf dries out and falls off, as if scorched. Then anthracnose moves to the fruit, where it leaves brown spots three to five millimeters deep. The infection can live for a long time in plant debris and soil.

Since the most common cause of vegetable infection with anthracnose is infected seeds, we recommend treating them before planting.

Remember about crop rotation. At the initial stage of the disease, a solution of colloidal sulfur (can be sold under the name Tiovit-Jet) and a 1% Bordeaux mixture are very good remedies. In addition, Alirin-B mixed with Gamair and green soap or Liposam for adhesion is suitable for controlling diseases.

Let's take stock

Growing cucumbers is not an easy task. The plant is susceptible to various diseases that you must recognize, distinguish and eliminate. The basic rules for preventing cucumbers from pests are mandatory weeding, meticulous inspection of each leaf, competent selection of the treatment solution and removal of infected leaves and fruits.

Tested by scientist - agronomist Alexander Zharavin

Yellow spots on the leaves of cucumbers worry many gardeners, because you can never be completely sure why they appeared. This could be a disease, a change in environmental conditions, a lack or, conversely, an excess of nutrients in the soil. The main thing is to ask yourself the question: “Why is this happening?” Varieties of causes of yellowing leaves, diagnosis and treatment - you will find all this in our article.

Causes of spots

It is worth understanding that cucumbers are rather fastidious plants that react by yellowing of the leaves to almost any irritant, regardless of the fact that all other conditions are fully met. This behavior can cause confusion, especially if the summer resident encounters this for the first time. Fortunately, most problems can be solved within a few days, a maximum of a week, by carefully fulfilling all the whims of the climbing crop. Let's look at what irritants and why most often cause spots on cucumber leaves.

Light

When placing beds with cucumbers on the site, you should remember that the plants do not like excessive shade, but at the same time do not tolerate the sun well. Often the leaves turn yellow from lack of light, especially on the lower part of the stem. Don't worry - this is a natural process. After the leaves fall off, new ones will appear in their place.

However, sometimes yellow spots appear due to too much exposure to sunlight. Yellowing is nothing more than burns. In this case, the leaves tend to curl into a tube. In most cases, excess lighting does not pose a danger to the plant, but during the flowering and fruiting period it is worth shading the plantings so as not to exhaust the cucumbers.

Temperature

Air temperature, especially too high, has a detrimental effect on the condition of cucumber leaves. Most often, the leaves of plants in a greenhouse turn yellow due to high temperatures.

If the thermometer reads 28°C or higher, expect a lot of yellowing. The air temperature suitable for healthy growth of cucumbers is between +23°C and +26°C.

Humidity

Maintaining balance in terms of watering different plants is a science. And rest assured, in some textbook on watering there would be a whole section dedicated to cucumbers! They do not tolerate excessive watering, since the roots lose the ability to breathe and rot. But cucumbers cannot live in dry conditions. In both the first and second cases, the cucumber leaves rapidly turn yellow, as if expressing a note of protest to the unbearable living conditions in an open garden bed or in a greenhouse.

Diseases

Fungal diseases are one of the most common reasons why yellow spots appear on leaves. Such symptoms are noted during the invasion of downy mildew, root rot, and verdigris. Fusarium and pythiosis often manifest themselves in this way. Favorable conditions for their occurrence are created by increased soil and air humidity, weak plant immunity, as well as ignoring safety precautions when planting seeds in open soil or in a greenhouse.

Insects

In addition to diseases, insects threaten the life and healthy growth of cucumbers. The most dangerous among them are whitefly and spider mites. Their harmful activity consists of absorbing the juices and tissues of the plant, until the moment it dies. Nowadays, treating the harmful effects of insects is easier than ever, so don’t worry too much.

Fertilizers

In the case of fertilizers, cucumbers turn yellow in two cases: when there is an excess of fertilizers in the soil, when the plant is globally fed, and when there is a lack of nutrients, when it is completely depleted and cannot cope with growth on its own.

It’s easy to determine which elements need to be added to the soil:

• yellowing at the edges indicates a lack of magnesium and potassium;
• darkened veins against a yellow background mean a lack of iron;
• if only the upper leaves turn yellow, this indicates a lack of copper.

Age

The only reason for yellowing that you can't do anything about is the age of the plant. The closer the end of the fruiting season is, the more the bush will turn yellow, since photosynthesis in it is inhibited, and soon stops altogether. Old fibers become stiff and conduct liquid less well. In such cases, you should remove the outdated plants from the garden and rejoice at the harvest that was collected from them.

How to treat?

If the leaves of the cucumbers are covered with yellow spots or even become yellow with a reddish tint, it is necessary to carry out a set of health measures, in other words, to begin treatment. First, determine the source to which the plant reacts this way. Find out why things turned out the way they did. This will help you understand what exactly needs to be done in the garden.

In the case of a lack of light, you need to thin out the plantings. Pinching shoots should already be done regularly to stimulate the development of female flowers. If the leaves turn yellow because there is too much sunlight, shade them by pulling an awning over the beds.

Temperature changes or too high temperatures in the greenhouse are normalized by regular ventilation, as well as by installing water containers around the perimeter of the building. Remember: if the temperature is too high or too low, it activates the activity of fungal diseases. Don't put your plants at risk.

If the reason is moisture, then you need to regularly test the soil moisture. Take a handful of earth from a depth of about 10 cm and squeeze it in your hand. Based on its condition, you can determine whether you should pour more water or, conversely, you need to pour a little less.

If you have not carried out antifungal prophylaxis, or it has not yielded results, then treatment of cucumbers should be started immediately. Plants damaged by fungus should be treated with fungicides. Treatment of downy mildew is carried out with the drug “Ordan”. Against root rot, you need to spray the bush and the ground around it with fungicides, iodine solution, and add a fertile layer of soil. Treatment of copperhead, fusarium, and pythiosis is carried out by treating with fungicides and adding a complex of nutrients. It is very important to immediately remove yellow or brown infected leaves, stems, fruits, and inflorescences from the bush.

A solution of boric acid or an infusion of onion peels will help get rid of insects. To prepare a boron solution, you will need to dissolve 1 g of boric acid in 1 liter of water. For onion infusion, pour 700 g of onion peel into 10 liters of water, boil the mixture, and leave to infuse for 14 hours. Both solutions are used both for spraying leaves and for watering the ground around plants.

If yellowing is associated with fertilizers, carry out unscheduled fertilizing with a complex of potassium, magnesium, copper, and water the plantings with a solution of potassium permanganate (it will also help disinfect the soil). If there is an abundance of fertilizers, especially nitrogen, mulch the soil with wood ash or sawdust.

If you want to prolong the growth of cucumbers and carry out rejuvenation, then use urea (urea) for foliar feeding. For 10 liters of water, take 25 g of urea. Under each bush you should add 1 liter of the prepared mixture.

Video “Problems of growing cucumbers”

Watch this video and you will learn what fatal consequences a growing mistake can lead to for plants, and what you need to do to avoid it.

In order for vegetables to develop well and produce full-fledged fruits, careful care and knowledge of disease and pest control measures are necessary. Unfortunately, weeding, fertilizing and watering alone cannot be done in the summer season. The cucumber also has its enemies. If you know them in person, then you can deal with the problem at the initial stage of development, and if you prepare for the meeting in advance, then many troubles can be completely avoided.

Cucumber flower. ©Korea

Cucumber diseases

Cucumbers have the same diseases as all melons. Basically, these are fusarium wilt, anthracnose, powdery and downy mildew, bacteriosis, cucumber mosaic, gray and white rot. Most often, damage is observed during prolonged wet periods of summer, when planting plants without observing crop rotation and frequent watering with cold water.

Fusarium

Withering and dying of cucumber vines indicates a fungal disease - fusarium. It is dangerous because spores of the fungus Fusarium oxysporum can be stored in the soil for up to 15 years and infect plants under unfavorable weather conditions. During prolonged rains or prolonged cold spells (below 10°C), the neck of the cucumber stem appears brown, which over time develops a pinkish or white coating.

As a result, one or several lashes wither, followed by the death of the entire plant. Most often, these symptoms are observed during the flowering period, but sometimes the disease also occurs on seedlings.

To prevent Fusarium wilt of cucumbers, it is necessary to observe crop rotation, choose seeds treated with fungicides for sowing (or treat them yourself), be sure to remove the remains of affected plants from the beds, and water with warm water.

In the initial stage of the spread of the disease, the vegetative part of cucumbers can be treated with Fundazol or Fitosporin-M. If the disease starts, it is no longer possible to help the cucumbers.

Fusarium on cucumber. © Farmer

Anthracnose

Blurry, round, yellow-brown spots with small cracks on cucumber leaves indicate that the plants have developed a disease called anthracnose. It usually occurs at high air humidity in combination with high temperature and affects not only the foliage, but also the stem, petioles, and fruits. On the latter, they can be observed in the form of ulcers, which often cause cucumbers to become unmarketable, rot, break stems, and die off vines.

Fungi that cause anthracnose (Gloeosporium, Kabatiella, Colletotrichum) are afraid of dry air and open sunlight. Therefore, when growing cucumbers, it is necessary to monitor their thickening, as well as weed the beds in time to remove weeds.

If the damage to the plantings develops rapidly and no improvement in growing conditions is observed (for example, there are prolonged rains), Bordeaux mixture, Burgundy liquid or any other fungicides recommended for use against anthracnose should be used.

Anthracnose on cucumber. © tinypic

Powdery mildew

White powdery spots on the upper surface of cucumber leaves indicate that the plant is affected powdery mildew. Typically, this disease “attacks” cucumber beds by the end of summer and, if left untreated, gradually spreads to the stems of the plant and its fruits. The danger of powdery mildew is that it gradually completely kills the cucumber bush.

The disease is favored by the following: sharp changes in day and night temperatures, watering with cold water, poor ventilation of plants (caused by thickening of plantings), cold drafts, excessive fertilizing with nitrogen. In the later stages of the development of the disease, it is almost impossible to help the affected plant, therefore, in August, when harvesting the fruits, it is necessary to inspect its vines for damage by the disease, and begin treatment at the first signs.

The first thing to do is to tear off and destroy the damaged leaves. The second is to fertilize with potassium fertilizer. Third, try spraying the plants with mullein infusion or dusting them with sulfur powder. If all else fails, you need to use one of the fungicides recommended against the fungi Erysiphe cichoracearum and Sphaerotheca fuliginea, for example, Bayleton or Copper Oxide.

Powdery mildew on a cucumber leaf. © konaprog

Downy mildew, or downy mildew

The cucumber leaves are covered with many small yellow spots - this is downy mildew or peronosporosis(its causative agent is Pseudoperonospora cubensis Rostowz). After a few weeks, the small spots will increase in size, a gray-violet tint will appear at the bottom of the leaf (a sign of sporulation of the fungus), the leaves will change color to brown and begin to dry out and crumble.

This disease affects cucumber plants at different stages. Increased air humidity and watering with cold water can provoke its spread. To help cucumbers survive, as soon as the first signs of downy mildew are detected, it is necessary to immediately stop feeding and watering, and treat the beds with a solution of Bordeaux mixture. If the first steps towards improving the health of your cucumber bed are not successful, you can try treating the cucumbers with Ridomil.

Downy mildew, or downy mildew, on a cucumber leaf. © Christian Hummert

Bacteriosis

Angular holes on the leaves and brown sores on cucumber fruits are a sign that the plants have been “attacked” bacteriosis. This bacterial disease (pathogen is Pseudornonas, Erwinia bacteria) spreads through contact: through insects, touching diseased parts of plants, with drops of water. As in all previous cases, the favorable moment for its outbreak is temperature changes and high soil and air humidity.

To defeat bacteriosis, it is necessary to sow cucumbers with treated seeds, observe crop rotation (without returning the crop to its original place for at least 4 years), and remove affected greens from cucumbers in a timely manner. For prevention, in places where the disease is widespread, it is recommended to treat cucumber beds with 1% Bordeaux mixture, 0.4% copper oxychloride or Fitosporin-M.

Bacteriosis on a cucumber leaf. © Clemson University

Green speckled cucumber mosaic and white cucumber mosaic

If young leaves of cucumbers become covered with yellow-green spots and then become wrinkled, plant growth slows down, the formation of flowers decreases and the fruits become variegated in color and warty - this is manifested green speckled cucumber mosaic, caused by the Cucumber green mottle mosaic tobamovirus virus.

If the spots on the leaves of cucumbers resemble the shape of stars, have a white or yellow color, fill most of the leaf (leaving mostly only the veins and the part of the tissue close to them green) and no wrinkling of the leaf blades is observed, and the color of the fruit includes white and yellow stripes - This white cucumber mosaic, caused by the Cucumis virus 2A virus.

These are mainly diseases of greenhouses, but they are also found in open ground, especially in areas with a warm-temperate climate. In order to avoid their spread, cucumber seeds must be disinfected before planting, garden tools must be pickled before the new season, the plants must be strengthened with fertilizers, and their affected parts must be treated with a 10% solution of skim milk.

Root rot is difficult to combat. First of all, you need to try to force the plants to produce additional lateral roots: hill up the stems or pin them to the ground and dig in the vines. In addition, start watering the cucumbers with exclusively warm water (not lower than 22 °C). And finally, stop pouring water directly under the root, and try to do it at some distance.

For biological remedies, you can try Trichodermin. There are currently no effective chemicals other than Previkur that can be recommended.

Root rot. © 500m2

Gray rot

Gray rot on cucumber fruits indicates that the plants are infected with a fungal disease with the same name - gray rot(pathogen: Botrytis cinerea F.). It occurs when there are sudden changes in temperature and high humidity in the air and soil. It can develop not only on fruits, but also on plant leaves, eventually moving to their lower part. Gradually, the affected foliage completely turns yellow and dries out.

The spread of gray mold occurs through contact of plants with insects and humans, as well as by air. Favorable conditions for this include sharp temperature fluctuations and thickened or weed-filled plantings.

Measures to combat gray mold are more related to prevention than treatment. To prevent the spread of the disease, it is necessary to pluck and destroy affected leaves and fruits, remove plant debris from the garden bed in the fall, and do not plant pumpkin crops nearby. Among the drugs you can try using “Euparen Multi” or “Rovral”.

Gray rot on cucumber. © Salem Khalil Nassr

A white coating appeared on the cucumbers - this is the beginning of a disease called white rot, or sclerotinia caused by the fungus Sclerotinia sclerotiorum. Under its influence, plant tissues decompose, as a result of which they become soft, slimy and begin to rot.

To prevent sclerotinia, it is necessary to constantly weed the beds and ensure that the cucumbers have sufficient ventilation - mushrooms love moist air and therefore, with proper agricultural practices, have less chance of spreading. If white rot does appear, it is necessary to temporarily stop watering and fertilizing the plants (for about a week), and then, at intervals of 7 days, spray the plantings with Topaz.

White rot, or sclerotinia. © Piglet in Portugal

Pests of cucumbers

Cucumbers and pests love them. The most harmful of them are slugs, melon aphids, greenhouse whiteflies, and spider mites.

Slugs or snails

If at night someone eats the young leaves of your seedlings, this is most likely slugs or snails. They are the ones who like to operate under the cover of darkness and consume young plant tissue. It is quite difficult to fight them, but it is still possible.

Firstly, this type of pest must be collected manually. To do this, you need to go out into the beds at night and use a flashlight to look for mollusks and remove them from the beds.

Secondly, you can set up traps in the area. These can be pieces of plywood, roofing felt or any other materials that do not allow light to pass through and retain moisture underneath.

Thirdly, the beds must be kept clean, with weeding and loosening in order to make life difficult for the little “enemies”. And, as a last resort, you can resort to using chemicals, for example, scattering Thunderstorm granules on the ground.

Slug. © ozz13x

Aphid

The cucumber leaves are curled, the flowers are falling off, a sticky coating has appeared in some parts of the plant - it works aphid. Typically, its mass distribution is observed in the middle of summer. Insects suck juice from plants, thereby inhibiting their development and contributing to a decrease in yield.

But the worst thing is that in addition to the direct negative impact, they often become carriers of diseases, so it is imperative to fight aphids!

• The first thing you can try is folk remedies. These include an infusion of garlic, onion peels, wormwood, celandine, ash and laundry soap, as well as dusting plantings with dry ash.
• The second is to carry out foliar feeding on the underside of the leaf with a solution of potassium chloride and superphosphate (10 g x 20 g x 10 l of water, twice, with a break of a week), or nitroammophos (per 10 l of water, 3 tbsp. once every 7 days ).
• Third, feed the plants with phosphorus-potassium fertilizers.
• And finally, treat the plants with biological preparations “Fitoverm”, “Strela” or insecticides “Arrivo”, “Intavir”, “Tanrek”.

Aphids on cucumber. © Penn State

If tiny white insects appear on cucumbers in large numbers, this is whitefly. It usually lives in greenhouses, but in hot, humid summers it also destroys open plantings. It is quite difficult to protect against it, since this pest is carried by the wind. However, control measures are still worth applying.

• The first thing you can use is glue traps. They are made independently by painting a piece of plywood or thick cardboard yellow and covering it with any slowly drying adhesive substance.
• Second, try to distract the pests by planting several tobacco plants next to the cucumbers.
• Third, simply wash off the pests regularly with water.
• And fourth - carry out regular spraying with the preparations “Bud”, “Karbofos” or “Iskra”.

Whitefly. © Ian Jacobs

Spider mite

A cobweb has appeared on the underside of the cucumber leaves - this has settled spider mite. This pest spreads massively in hot, dry weather. Its target is plant cell sap. That is why, where it appears, cucumber leaves acquire a marble color, gradually turn brown and dry out.

To minimize the risk of this harmful insect settling in the beds, during hot weather they must be sprayed with water, thereby maintaining optimal air humidity, and regular weeding must be carried out. In case of massive infestation of cucumbers by spider mites, it is recommended to use the drug “Fitoverm”.

Spider mite on a plant. © Jasper Nance

Other reasons for modification of cucumber fruits or leaves

Strange manifestations on cucumber fruits and leaves are not always a sign of disease or pest damage. Often external changes that appear on one or another part of the plant indicate a deficiency of one or another element in the soil.

Pear-shaped fruits- a consequence of potassium deficiency. To change the situation, you need to feed the cucumber plantings with ash or potassium sulfate.

Cucumbers in the shape of a jug or an inverted pear - this is a lack of nitrogen. Here, nettle infusion, ammonium or potassium nitrate are suitable as a life-saving fertilizer.

Unnaturally light foliage of the upper part of the cucumber vines, drooping lower leaves, slow plant growth and small fruits are also a manifestation of the need for nitrogen fertilizing. In addition to the measures listed above, mullein, bird droppings or ammophosphate can help here.

The leaves of cucumber plants look like they are scorched, acquired fragility and a pale green or yellowish color, but at the same time retained the green color of the veins - this is a lack of magnesium. However, excess moisture can also result in fading and a change in the color of the plant to light. This effect is often observed during prolonged bad weather, with excessive rainfall.

Unnaturally dark brittle leaves cucumbers, on the contrary, indicate a lack of moisture. In this case, it is necessary to take care of regular watering.

Falling color, small leaves, bluish-purple tint - manifestations of phosphorus deficiency. Here you need urgent feeding with a complex fertilizer containing this element. However, flower abscission can also occur when plants are insufficiently pollinated. Here, attracting bees (with the help of aromatic solutions and planting flowering plants) or artificial pollination should come to the rescue.

Cucumber. © Brian Kimball

Prevention of diseases and pests of cucumbers

As practice shows, in order to reduce the risk of illness and damage to cucumbers by diseases and pests, and to maintain the plants in a healthy state, it is necessary to observe a number of preventive measures:

• Apply crop rotation;
• Select seeds of varieties and hybrids that are resistant to a number of major diseases;
• Before sowing, be sure to treat the seed material;
• Follow watering rules;
• Feed the plants well;
• Respond in a timely manner to the first signs of crop damage by diseases and pests;
• Remove affected parts of plants from the beds;
• Fight weeds;
• After the end of the growing season, carefully remove plant debris from the garden (greenhouse).

If you, dear readers, have your own secrets for preventing or combating diseases of cucumbers and their pests, we will be glad to read them in the comments to the article.

Many families who have a small plot of land prefer to grow vegetables, such as cucumbers. This will allow you to enjoy environmentally friendly fruits during the summer and make pickles and baked goods for the winter. However, growing these seemingly unpretentious plants is fraught with some difficulties. Many gardeners complain about the appearance of yellow leaves on cucumbers. The reason for this phenomenon is unknown to many - perhaps a disease or a lack of something. Let's figure out why cucumber leaves turn yellow and how to deal with it.

Yellow spots on cucumber leaves: causes

1. Most often, damage to the leaves of this wonderful vegetable is associated with unfavorable environmental conditions and diseases. For example, a fungal infection such as anthracnose manifested by the appearance of yellow and light brown spots on the stems and leaves of the cucumber. It usually occurs due to excessive air humidity, which is typical for greenhouse cultivation of watery vegetables. Over time, these spots become sores filled with pink mucus.
2. The reason why cucumber leaves turn yellow in spots may be another disease - ascochyta blight. This is also a fungal infection, which can be suspected by the fact that the cucumber leaves turn yellow at the edges, and there are also light brown and light gray spots that are covered with black dots - spore-bearing particles of the fungus. Such manifestations appear first on the lower nodes of the plant stem. Then the lower leaves of the cucumbers turn yellow - the weakest and least illuminated. Ascochyta blight quickly spreads throughout the vegetable, and the fruits become affected: the stalk turns yellow, and then the fruit itself withers and turns black.
3. There is also a disease of cucumbers, when the leaves turn yellow: spots appear on the upper part of the leaf along the veins, while the lower side is covered with a gray-purple coating - spores of the causative fungus peronosporosis, or downy mildew. As the infection progresses, these oily spots turn brown, the affected leaf tissue falls out and the plant dies.
4. The reason why the leaves of cucumber seedlings turn yellow may be mosaic- viral disease. It usually develops on the leaves of young plants in the form of white-yellow spots in a star shape.
5. Blackleg is a fungal disease characteristic of seedlings. First, the root system becomes affected, then the cotyledon leaves of the cucumber turn yellow (the first two), and the root collar turns brown. The disease is dangerous because it often leads to mass death of seedlings.
6. Sometimes causes yellowing of leaf edges potassium deficiency. If the parts of the leaves between the veins turn yellow on the leaves, this is how magnesium deficiency.

What to do if there are yellow spots on the leaves of cucumbers?

If anthracnose is detected, all affected plants should be removed to prevent infection of the entire planting. If the first symptoms of the disease appear, you need to spray the cucumbers with the so-called 1% Bordeaux mixture - a solution of copper sulfate and lime (100 g of each substance per 10 liters of water).

the root part of the cucumbers with Bordeaux mixture.

At the first symptoms of downy mildew, cucumber plantings can be treated with a solution of potassium permanganate, taking 2 g of the substance per 10 liters of water. In case of serious lesions, special fungicides are needed to combat the disease.

If plants are affected by blackleg, watering with a weak solution of potassium permanganate will be required.

When mosaic occurs, the main measures are reduced to the destruction of single affected plants and treatment of the soil with a 5% formaldehyde solution.

womanadvice.ru

White spots on cucumber leaves. Diseases of cucumbers. Prevention and treatment

Cucumber is a very common and beloved vegetable that can be found in every garden. When growing cucumbers, a gardener faces various problems: the fruits begin to wither, white spots appear on the leaves of the cucumbers, the leaves curl, etc. To avoid all these problems, you need to carefully study how to care for the vegetable, how cucumbers should be processed, and much more. You will read about all this in this article.

Important facts to know

The first thing you need to know before planting cucumbers is that the vegetable comes from the tropics, and therefore loves warmth, humidity and sunlight. Of course, they can grow in the shade, but don't count on a rich harvest. The vegetable requires loose soil with an average level of acidity. For this purpose, the bed chosen for cucumbers must be dug up in the fall, and leveled and fertilized with manure or droppings in the spring. It is also very good to plant cucumbers in a bed where corn, potatoes or tomatoes previously grew. Cucumbers should not be watered with cold water. You need to monitor the acidity of the soil - there will be no harvest in acidic and unfertilized soil. Temperature changes also have a bad effect on the vegetable: it becomes bitter. And at temperatures below 11 degrees, cucumbers do not grow at all.

Growing methods

Growing cucumbers is possible using seedlings or seeds. If the seedless method was chosen, then the seeds need to be prepared by placing them in a wet, warm place so that they swell and germinate. You can plant seeds only when the soil has warmed up to 150. It is recommended to place the seeds in the hole not flat, but edge-on. As for the distance, about 20 centimeters should be spaced between seeds, and the rows should be a meter apart. Seeds can germinate on the 4th-12th day, depending on the temperature.

In warm weather, seedlings will appear much faster. If the seedling method is chosen, the seeds should be planted about a month before planting in the ground. Cucumbers are planted only in warm soil. It is recommended that before planting seeds or seedlings, put stale manure and hay into the dug holes, sprinkle with soil and water it all.

Cucumbers: open ground (care)

The main condition for proper care of cucumbers is regular watering. It is best to water using the drip irrigation method. This allows moisture to flow directly to the root, reduces the amount of water and does not provoke the growth of weeds. Watering cucumbers should be done with water at room temperature or warm, so running water will not work. It is recommended to prepare a container for this purpose in which the water will stand all day and warm up.

Watering is necessary depending on the condition of the soil. Watering too frequently can damage the crop, causing the cucumbers to develop stems and trail instead of producing fruit, or they may develop white spots on the leaves. In very hot weather, watering is needed more often, otherwise the leaves will wilt. You can freshen the leaves a little with a shower of cool water. It will wash away dust, increase humidity and photosynthesis will improve. If the leaves are still limp, you should pierce the ground with a fork so that water penetrates to the root system.

You can water in three passes, one watering can per hole at a time; wait until the water is absorbed into the ground and water again and again. Also, in addition to watering, it is important to regularly weed the beds to remove weeds. They do not allow the plant to fully develop and create unnecessary shading.

Feeding cucumbers

Cucumbers need to be fed every ten days. The solution is prepared in the proportion of 30 grams of saltpeter and a liter of mullein per ten liters of water. When the cucumbers begin to bloom, add 50 grams of potassium salt and 50 grams of superphosphate to this solution. The consumption will be one liter of fertilizer per four bushes. It is important to feed cucumbers in the evening so that the solution that gets on the leaves does not lead to burns in sunny weather. If the solution does get on some leaves, you need to wash them off with water, pouring them from a watering can. After fertilizing, you need to add soil to each bush, which replaces loosening. The root system of cucumbers is close to the surface and loosening the soil can damage the roots. Therefore, they loosen the soil only between the rows.

Growing cucumbers in a greenhouse

Planting cucumbers in a greenhouse is done when the ground under the glass or film is thoroughly warmed up. Growing cucumbers in a greenhouse is a rather troublesome process. You need to carefully monitor the temperature, because cucumber does not like sudden daily temperature changes. It is imperative to maintain humidity inside the greenhouse using irrigation. It is better to do this with rainwater.

If the weather is sunny and hot, it is necessary to ventilate the greenhouse. Cucumber does not like drafts, therefore, it needs to be ventilated carefully. It is very important to allow bees to pollinate flowers. Folk remedies for processing cucumbers will help here. Bees are not very willing to fly into enclosed spaces, and this can significantly reduce the yield. In order to attract the attention of insects, cucumber leaves in the greenhouse are sprinkled with sweet syrup. Between the rows of cucumbers you need to put fertilizer, which cucumbers really need, especially at an early stage of development. Watering should be done not at the root, but along specially made hollows near the roots. In this case, you need to water only with warm water, and this should be done in the middle of the day. It is best to use drip irrigation in a greenhouse.

Types of greenhouses

For those who want to grow cucumbers in a greenhouse, it is worth saying that the latter can be completely different. The base of the greenhouse can be made of metal, plastic or wood. It can be sheathed with glass, plastic or film. The main thing is that the material allows sunlight to freely penetrate into the greenhouse.

A metal frame will last the longest, but its construction will cost the owner a lot of money. A wooden frame is cheaper, but it will not last very long due to high humidity, even if it is treated with special means. There is also a plastic frame. This material is most often chosen because of its low cost and ease of care: it does not need to be painted, impregnated, etc. But plastic can be deformed in extreme heat.

Greenhouse sizes

As for the dimensions, the ideal dimensions for a greenhouse are three and a half by two and a half meters. Of course, the dimensions may be different, but it is not recommended to make it more than six meters in length. In such a greenhouse, caring for and processing cucumbers will be more difficult. It is better to divide it into several sectors. The doors should be wide enough to allow access with equipment and ventilation if necessary. If you follow all the recommendations, you won’t have to watch later how white spots appeared on the leaves of the cucumbers or the branches dried out and the leaves twisted.

Pests dangerous to cucumber

• Spider mite: sucks the juice of plants, white spots appear on the leaves of cucumbers, and they dry out.
• Melon aphid: located on the underside of leaves, causing them to curl and dry out.
• Sprout fly: penetrates inside the stem, it withers completely or the plant grows very weak.
• Whitefly: sucks the juice from the leaves, secretes fungal spores, which cause the leaves to turn black and dry.
• Cucumber mosquito: found more often in greenhouses, it attacks the stems and roots of the plant, which begin to rot.

The general rules for protecting against pests are regular weeding of cucumbers, careful regular inspection of plants and timely treatment with appropriate medications.

What are the diseases of cucumbers?

Gardeners who grow cucumbers from year to year are well acquainted with all the pests that threaten a good harvest. But not only insects can be the reason why there are white spots on the leaves of cucumbers. Cucumbers can also fall victim to a disease that affects not only the leaves, but also the fruits and seeds of the plant and leads to its death.

Diseases of cucumbers are as follows:

• Anthracnose: one of the reasons why white spots appear on the leaves of cucumbers. They look like they have been burned and eventually dry out completely.
• White rot: occurs more often in greenhouses, affects the entire plant, it becomes soft and as if covered with mucus.
• Powdery mildew: most often it is the answer to the question of why white spots appear on the leaves of cucumbers. You can find out what to do with these stains in a specialized store. The leaves seem to be sprinkled with flour, dry out and the cucumber dies.
• Brown spot: affects the fruit, spreads during watering, the cucumber becomes stained and should not be eaten.
• Gray rot: affects the stems of the plant in the form of gray slimy spots, does not allow the plant to develop, it rots and dies.
• Common mosaic: green spots of light and dark tones appear on the leaves, swollen leaves, tuberosity on the fruits.
• Fusarium: found mainly in greenhouses, the upper part of the plant withers, then rot descends to the root and the plant dies.
• Cucumber necrosis: a lack of necessary substances leads to the formation of spots on the leaves, the plant stops blooming, growing and dies.
• Cucumber bacteriosis: affects seeds, fruits and leaves. The seeds dry out, the leaves become holey and dry out, the fruits become covered with ulcers and become distorted.
• The mosaic is light: light spots appear along the leaf veins, the leaf turns yellow, the plant weakens and stops developing.
• Root rot: affects the root system of the plant, spots appear on the stems, they rot and become covered with mucus, the leaves wither and the plant dies.
• Black leg: affects the root, it becomes weak, rotten and soft, the leaves wither and the bush dies.

Methods of prevention and treatment

There are many ways to deal with adversity. To grow cucumbers without problems and get a wonderful harvest, it is necessary to regularly carry out disease prevention measures. Moreover, these measures must be both technical and chemical. It is necessary to carefully remove plant remains during the harvesting period; the top 6-7 centimeters of soil should be removed or replaced, and the soil should be disinfected. It is also necessary to spray the plant for prevention. If cucumbers are grown in a greenhouse, then the entire structure must be disinfected, including the frame, walls, trellises and soil. The correct climate inside the greenhouse should be maintained to prevent disease from affecting the plant. Much attention should be paid to seeds, because many diseases are transmitted through seeds. It is usually sufficient to soak the seeds in a concentrated solution of potassium permanganate.

Medicines for treating diseases

Despite all the mechanical procedures, the plant also needs chemical exposure - both for treatment and for prevention. In specialized stores you can find any necessary drug, depending on the problem. For example, “Trichodermin” (used to treat root rot, wilt, powdery mildew), “Pentafag” (used for seed treatment), “Quadris” (good in the fight against powdery mildew), “Topsin” (for the prevention and treatment of fusarium, powdery mildew) and many other drugs.

syl.ru

Common diseases of cucumbers: descriptions and photos of diseases

At various stages of development, vegetables are susceptible to dangerous diseases. As a result of the defeat, the cucumbers turn yellow, spots appear on the leaves of the cucumbers, the plants weaken and even die.

Root rot can cause cucumber leaves to turn yellow.

This disease of cucumbers appears when the soil temperature sharply decreases and when watering at cold temperatures. If you use soil in which pumpkin crops have previously been grown, the risk of the disease increases. Root rot can also occur if planting is done incorrectly. If it is not clear why the leaves of cucumbers turn yellow, then you should pay attention to whether there is premature wilting and cracks on the lower part of the stem. If these signs are found, then it is possible that it is infected with root rot.

To prevent disease, you must strictly follow the rules for planting seedlings. The stems should not be planted too high.

If the disease has been detected, then the soil is raked from the stem to the very roots. And they are treated with a solution of copper sulfate, polycarbacin or copper oxychloride. Plants that have died from the disease should be dug up and burned. The soil from them is treated with a solution of copper sulfate.

If the ovaries of cucumbers turn yellow, then this is bacteriosis

Gardeners often encounter cucumber ovaries turning yellow or even rotting. The reason for this may be a cucumber disease such as bacteriosis. Its spread is facilitated by high soil or air humidity.

Gray spots on cucumber leaves can be caused by a cucumber disease called gray rot.

At low night temperatures, with poor ventilation and when watering with cold water, gray spots may appear on the leaves of cucumbers, in the axils of the leaves and on the stems. These are signs of gray rot. To prevent it from forming, it is necessary to prevent the plants from becoming too crowded, not to water them with cold water, and to ventilate the room frequently.

Ascochyta disease is why cucumbers turn yellow and why cucumber leaves turn yellow

This disease affects leaves, stems and fruits. First, large yellow spots appear, then they are replaced by gray ones. Afterwards, black dots appear on the plant. In case of damage, it is necessary to spray with Bordeaux mixture. If it is not clear why cucumbers turn yellow, then it is worth examining the fruits for signs of ascochyta blight.

Sclerotinia or white rot

It affects all organs - petioles, fruits, leaves, tendrils, stems. A white coating forms on the tissues, after which they soften and rot. First, white and then black fruiting bodies appear on the affected areas. They are called sclerotia. They are the cause of infection. Sclerotia overwinter in the soil. When the air or soil is too wet, rot will spread. The affected areas should be sprinkled with fluff lime or charcoal.

Plants are most often susceptible during the fruiting period. The formation of rot can also be caused by temperature changes and thickened plantings. It is imperative to alternate cultures. Sprinkle stems with signs of damage with lime. The affected parts must be cut out, partially including healthy tissue. If the infection is very widespread, it is better to remove the sheets during hot hours - this way the wounds will dry out faster. The sections are sprinkled with crushed coal or wiped with a solution of copper sulfate. Provide regular ventilation. Watering is carried out in the evening with warm water. You can try feeding. For ten liters of water, use ten grams of urea, one gram of zinc sulfate and two grams of copper sulfate.

Other fungal diseases of cucumbers in open ground: spotted blight, cladosporiosis

Anthracnose or spot burn is characterized by light brown spots that have an irregular shape. As a result of the damage, the fruits do not grow to the required size, and in severe cases they disappear.

The next fungal disease of cucumbers in open ground is olive spot or cladosporiosis. First, an olive coating appears on the plant, then the tissues become depleted and crumble. Then spots appear on the fruits. You can look at photos of cucumber diseases to better recognize cladosporiosis.

Photo gallery of diseased cucumbers (click to enlarge):

udec.ru

What diseases do cucumber seedlings suffer from?

If you decide to start growing a vegetable such as a cucumber, then it will be useful for you to know what diseases of cucumber seedlings exist.

There is a fungal infection called blackleg. Favorable conditions for this infection are waterlogged soil and a fairly high temperature of the room in which the seedlings are grown. To reduce the likelihood of blackleg occurring, you can add wood ash to the ground before planting.

The following situation occurs very often: a plant grows and develops normally, but at a certain moment it suddenly stops growing, may wither or even die. This can happen if you water the seedlings with cold water. The fact is that the roots of cucumbers simply die and rot due to cool water. If you put a glass of cucumber on a cold windowsill, the same thing will happen.

There is also a disease of cucumber seedlings called mosaic. This is a viral type disease, it appears on the leaves in the form of light spots, the cucumber leaves wrinkle. When the seedlings are still very small, it is almost impossible to cure them of this disease; the diseased plant must be removed.

OgorodSadovod.com

The question of why cucumbers turn yellow in a greenhouse worries every gardener and gardener who grows them indoors. There may be several reasons that cause yellowing of leaves, ovaries and cucumbers grown in greenhouse or greenhouse conditions.

Possible reasons

• Insufficient pollination, and as a result, poor setting;
• Overload of plants with ovaries;
• Damage to plants by insects or fungal infections;
• Possible violation of agricultural technology for growing cucumbers:
  1. frosts or low average daily temperatures;
  2. lack of mineral elements in the soil;
  3. insufficient amount of moisture at high ambient temperatures.

Having listed the main reasons why cucumbers turn yellow in a greenhouse, we will consider each of the listed problems in more detail.

Violation of agrotechnical conditions

Low temperatures and frosts

Cucumber, as you know, is a warm and moisture-loving plant. In the middle zone, especially at the end of May, so-called "return frosts". Cucumber seedlings planted under film covers or in greenhouses may not only turn yellow, but also stop growing and developing.
To avoid cucumber leaves turning yellow in the greenhouse, it is necessary to additionally cover the planted plants with lutrasil or bubble wrap. Many gardeners, in sub-zero temperatures and frosts, place plastic bottles with hot water under such shelter in order to maintain a normal temperature for the growth and development of cucumbers.

Attention: It is important to remember that this plant prefers temperatures within +22+260C for its development. If the temperature drops below +140C, or above +420C, the plant stops its growth and development. If the temperature is below -10C, the cucumber seedlings will die.

Thus, in order to protect cucumbers planted in a greenhouse from frost and low temperatures, they should be additionally covered with a film placed on the arcs or with a special non-woven covering material such as lutrasil, agrotex or spandbond. This is what will help maintain an acceptable temperature for plants in the greenhouse.

Lack of mineral elements in the soil

Also, the reason why cucumber leaves turn yellow in a greenhouse may be a lack of minerals in the soil in which the plants were planted. As a rule, the leaves of cucumbers in a greenhouse turn yellow due to a lack of nitrogen.
Yellowing begins with the leaves having a lighter color, and then completely turning yellow, both the veins themselves and the entire space of the leaf between them. Subsequently, all the lashes of the plant turn yellow. Another sign indicating a nitrogen deficiency in the soil is the incorrect, “ hook-shaped fruit shape.
A lack of nitrogen in cucumbers can be caused by excessive application of wood ash, potassium fertilizers or superphosphate. In order to avoid nitrogen deficiency in cucumbers, it is recommended that cucumber seedlings, a few days before planting in greenhouses, be fed with fertilizers and sprayed with a solution of microelements (see How to choose the right fertilizers for cucumbers in a greenhouse).

When digging up a greenhouse in autumn and spring, it is necessary to add rotted manure to the soil at the rate of two or three buckets per 1 m2. This will help avoid nitrogen starvation in plants.
If manure was not introduced during the digging process, then before planting the seedlings in the greenhouse, you can add rotted mullein to the soil, and throughout the growing season, feed the plants with an aqueous solution of mullein or chicken droppings, as well as an infusion of herbs, which is also called “herbal tea."
The addition of mineral fertilizers containing nitrogen will also help eliminate the lack of nitrogen in the soil. The leaves of cucumbers in greenhouses also turn yellow when too much mineral fertilizer is added to the soil.
Before applying any fertilizer, carefully read the manufacturer's instructions on the package.

Insufficient watering

Cucumbers are moisture-loving plants and require both frequent watering and high humidity in the greenhouse or greenhouse where they are grown. However, watering these plants should be done only with warm and settled water.
Cucumber leaves turn yellow in a greenhouse both from watering with cold water and from insufficient water. At a time when active fruiting occurs, watering should be increased.
It is necessary to moisten the soil quite deeply, since it is the deep penetration of water that will contribute to the development of not only the surface, but also the deeper root system of plants.
Irregular and insufficient watering will affect both the leaves themselves and the ovary and fruits of cucumbers.

Poor pollination

One of the reasons why cucumber ovaries turn yellow in a greenhouse may be poor pollination of flowering plants. This can happen due to the fact that only artificially pollinated plants were planted, as well as due to the lack of ventilation or access for insects to pollinate the plants (see How to attract bees to grow a good harvest).
In this case, you can use spraying with boric acid dissolved in water (5 grams per 10 liters of water), or drugs "Bud" or "Ovary".Natural methods include spraying with sweet water (one tablespoon of sand or honey dissolves in two liters of water), which will attract insects.
Next season, in the greenhouse in which you plan to plant cucumbers, plant dill or some honey plants, for example, borage, hyssop. These plants will be able to attract insects to the greenhouse, which will be able to pollinate the plants and promote the formation of normal ovaries.

Plant overload with ovaries

In the literature devoted to gardening and growing cucumbers in greenhouses, when asked why cucumbers turn yellow in a greenhouse, they answer that it is not advisable to leave more than 20-25 ovaries on one plant at a time.

This is due to the fact that in greenhouse conditions cucumbers develop quite quickly. In many hybrid varieties, it is possible to form more than one hundred and fifty ovaries on one plant at a time.
It is necessary to pinch out new shoots in a timely manner to allow cucumbers to form and ripen normally. If excess shoots and ovaries have not been removed, the fruits may develop an unattractive shape, and cucumbers in the greenhouse may turn yellow.

Damage to plants by insects or fungal infections

So, let's figure out what insects and diseases can harm cucumbers, and how to deal with them (see Diseases of cucumbers in a greenhouse, causes and methods of treatment).

Fungal diseases

Fusarium wilt or fusarium is a fungal disease

This disease manifests itself as follows: cucumbers sprout normally and grow well, but as soon as the ovaries begin to appear, the leaves of the cucumbers in the greenhouse first turn yellow, after which the vines dry out.
The fungus that causes this disease penetrates the plant and releases toxins that limit the supply of nutrients and microelements to the leaves and stems. The way to combat this fungal infection is to regularly change the varieties planted in the greenhouse, as well as partially replace the affected soil.
Powdery mildew is also a fungal disease. In this disease, the fungus blocks photosynthesis processes in the plant.
First of all, small light spots appear on cucumber leaves, which gradually spread to the entire surface of the leaf.
On all leaves of the plant, a whitish or reddish coating is observed on the upper surface of the leaf blade. After which the leaves of the cucumbers in the greenhouse turn yellow and dry out.

To prevent the disease from visiting your greenhouse next season, you need to take a number of measures. First of all, when choosing cucumber varieties for the next season, pay attention to the resistance of a particular variety to powdery mildew, and also annually treat the soil in the greenhouse with potassium permanganate or green manure.

Downy mildew (pernosporosis)

The appearance of such a disease in greenhouses is facilitated by very densely planted plants, as well as excessive humidification of the air and soil in the greenhouse. The first signs of the development of peronosporosis are the appearance of yellow and light spots on the leaves, which are limited by the veins.
Subsequently, the spots become oily and light yellow, and eventually turn brown. On the underside of the leaf blade, in those places where there are spots, a grayish-brown coating forms. If no measures are taken, the plant will die within a few days.

If cucumbers in a greenhouse turn yellow, root rot may also be the cause of this phenomenon. Plants at any stage of development can suffer from this disease.
The reason for such damage to cucumbers can be a significant difference in night and day temperatures, as well as watering the plants with cold and unsettled water. Weakened plants are the first to be affected, and then other plants become infected through the soil.
In order to prevent plants from being affected by this disease, it is necessary to treat the root area with Previkur twice per season, according to the instructions.

Insect pests

melon aphid

This pest prefers to “infest” the underside of cucumber leaves and feeds on plant sap, which is why cucumbers turn yellow in greenhouses. The melon aphid poses a threat to cucumbers throughout the summer season.

This pest appears primarily on the inside of the cucumber leaf, where it weaves small webs.

First, white or light yellow spots appear on the leaf, and then the leaves become completely covered with yellow spots and dry out. Throughout the warm days, spider mites multiply and if you do not fight them, for example, with the preparations “Akarin”, “Tsimbush”, “Fitoverm” and others, then you can lose all the plants in the greenhouse.

parnik-teplitsa.ru

why do white spots appear on the leaves of cucumber seedlings?

Petr Yurievich

Possibly spider mite or whitefly

Vitalik Andrusenko

get some ladybugs

Lesnaya

Most likely powdery mildew. Occurs due to improper care. Sudden temperature fluctuations, low or too high humidity, watering with cold water. In general, the reasons can be completely different.
To avoid using chemicals now, try a folk remedy. Dilute the whey 10 times with water and spray the leaves.

Diseases of cucumbers in a greenhouse: description photo video

The conditions that are created indoors when growing vegetable plants, in particular long-term use of soil, a limited range of crops, and an artificial microclimate, contribute to the massive development of diseases.

The most common infectious diseases of cucumber in greenhouses are root and basal rot, wilt, white and gray rot, ascochyta, powdery mildew, downy mildew, bacteriosis, brown spot, olive spot, anthracnose, black mold, alternaria blight, etc.

We will now consider these and some other diseases in detail.

Root and basal rot

They affect seedlings, seedlings and adult cucumber plants. Small brown streaks and spots first form on the roots, which enlarge and merge. The roots of seedlings and seedlings rot and die. Affected seedlings die.

The roots of adult plants, depending on the pathogen, become brown, crack, especially the main one, or turn black and macerate, or become covered with dark brown wet spots or light brown dry spots. Similar symptoms appear on the root part, as well as possible growth of the root collar .

Interceptions may form on the lower part of the stem with or without rotting. On a cross section of the stems of affected plants, browning of the blood vessels can be seen. The stems are stunted in growth and wither. The leaves of the seedlings are often deformed with small brown spots. On the leaves of adult plants, interveinal chlorosis and necrosis similar to magnesium starvation can be detected.

Root rot is a consequence of the action of a complex of pathogenic fungi with Fusarium, Pythium, Rhizoctonia, Phytophthora, Phomopsis. All pathogens persist in the soil. The pathogen Fusarium root rot can persist in cucumber seeds.

The development of the disease is promoted by sowing seeds in cold, waterlogged soil, watering with cold water, a sharp drop in soil temperature (below +16 º C) or overheating (above +28 º C), excess nitrogen, and excess organic background. Cucumber root rot can also be non-infectious in nature. In this case, the vessels at the roots turn brown, the tissues peel off, and cylindrical cavities form around the vascular bundle.

Wilting cucumber

This problem is caused by the fungi Fusarium oxysporum, Verticillium albo-atrum and V. dahliae, which cause harm throughout the growing season. Pathogens penetrate into plant vessels from the soil through the roots, develop there, clog the vessels and release toxins. On cucumber stems near the ground, the vessels become silvery-white, and on the cross section the browning of the conductive system is clearly visible. Sometimes a white or pinkish coating of sporulation of pathogens appears on the stems. The lower leaves wither during the daytime, and at night their turgor is restored. Later the leaves become chlorotic and die. Sick plants grow poorly, their fruits are small and have low taste.

Also, plant wilting can be caused by underdeveloped cucumber roots when the seedlings were planted in dense soil, which mechanically compresses the root system, and water and nutrients cannot enter the plant.

The causative agents of infectious cucumber wilt can persist in the soil for a long time, and Fusarium wilts can also survive in seeds.

White rot

Its causative agent is Sclerotinia sclerotiorum (Whetzelinia sclerotiorum), a polyphagous fungus that attacks a wide range of plants, both cultivated and wild. Develops on vegetative stems, leaves and fruits of cucumber.

At the base of the stems, the tissues become wet, become covered with a white, cotton-like coating of mycelium, and become wet. The stem dries up and the leaves droop. In addition to the root part, white rot can also appear higher up, especially in branching areas. As plaque thickens, black sclerotia may form. Diseased fruits look boiled and are also covered with plaque.

The development of the disease is facilitated by thickened crops, high air humidity, insufficient ventilation, and temperature fluctuations. The source of the primary infection is soil and plant debris with sclerotia.

Gray rot

The causative agent is the fungus Botrytis cinerea, which affects all above-ground organs - stems, leaves, flowers, ovaries, fruits.

In the affected areas, watery soft spots appear, covered with a gray powdery coating, and among it are flat black sclerotia.

The conditions for the development of the causative agent of gray rot are the same as for the causative agent of white rot.

The infection persists in the off-season in the soil and on greenhouse structures.

Ascochyta blight

Ascochyta melonis affects seedlings and adult plants. On seedlings, watery, wet spots with numerous black dots - pycnidia - form in the root part of the stem. Subsequently, an interception is formed.

In adult plants, stems, leaves with petioles and fruits are affected. The stem form appears at the places where the petioles are attached. Diseased areas of the stems become dry and almost black due to numerous pycnidia. Around these areas, parts of the stem are grayish-white, dry, cracking, and wet.

Large, initially yellow-brown, blurry spots form on the leaves, which later lighten, become covered with black pycnidia, merge and cover a significant part of the leaf blade, and sometimes more. Diseased leaves, starting from the bottom, dry out. When fruits are affected, black pycnidia also form on their surface, especially at the point of attachment to the stalk. The fruits become as if boiled, but do not soften, but dry out. The pathogen spreads during the growing season by pycnospores, which are spread by splashes, drops, water flows and air currents. The infection persists on plant debris, and seed infection is also possible.

The development of cucumber diseases is promoted by high air humidity and the weakened state of plants.

Downy mildew

The pathogen Pseudoperonospora cubensis appears on cucumber leaves of different ages. Yellow-green round, angular or indefinitely shaped spots form on the upper part of the leaf blade. Below, under palm trees, in damp weather, a gray coating forms, consisting of conidial sporulation of the fungus. Diseased leaves become brown, brittle, they curl and dry out. When the damage is severe, the plants die. For the development of the fungus, drip moisture, air humidity of 90-100% and a temperature of +16 ... +20 º C are required.

The infection persists in plant debris and seeds.

Powdery mildew of cucumber

Its causative agents are Sphaerotheca fuliginea Erysiphe cichoracearum. Plants are affected starting from the stairs. Cotyledon leaves and leaves and petioles of adult plants are first covered with a thin white or pink-gray coating, which represents conidial sporulation of pathogens. The plaque is predominantly located on the upper side, first in separate spots, later - continuous. Numerous small, black dots form on the plaque - marsupial sporulation - cleistothecia, which are not often observed in open ground. Diseased leaves turn yellow, become deformed, and die. Sometimes stems and fruits become covered with bloom.

In a greenhouse, the infection is introduced mainly from open ground in the fall (with autumn-winter cucumber crops) or early summer (with spring-summer crops), and also persists on plant debris.

The development of the disease is made possible by sharp fluctuations in humidity and air temperature, drafts, lack of light and the optimal temperature for the pathogen +16 ... +20 º C, and withering of plants. More often, pockets of powdery mildew begin at doors, transoms, and heating pipes.

Anthracnose (scarden)

It is caused by the fungus Colletotrichum lagenarium, which develops on cucumbers during the growing season on leaves, stems and fruits. Yellowish-brown, mostly round spots appear on the cotyledons and leaves. The tissues in the spots become necrotic and crumble.

Deep spots, in the form of ulcers, are formed on the fruits - single or in groups. In humid weather, spots become covered with a pink-copper coating, which darkens over time and becomes black and dense. Diseased fruits are bitter and rot during transportation and storage.

The stems and petioles are covered with deep, elongated spots, on which a pink coating of conidial sporulation of the pathogen also forms. During the growing season, the pathogen is spread by conidia by airborne droplets. The infection persists in plant debris and infected seeds.

Favorable conditions for the development of the pathogen anthracnose in cucumber are high air humidity - about 90% and elevated air temperature - +22 ... +27 º C.

Bacteriosis (angular spot)

The disease is caused by the bacterium Pseudomonas lachrymans. The first signs can be detected on the cotyledons when light brown small spots or ulcers appear. Angular spots bounded by veins form on the leaves. At first they seem to be soaked in water or oily, but later they turn brown. In humid weather, bacterial exudate appears on the underside of the leaf under the spots, in the form of a cloudy drop. Subsequently, diseased tissues dry out, die and fall out, forming holes.

There are small spots on the stems and petioles that deepen over time. There are also ulcers on the fruits, but they are deep, as if pecked by birds. Exudate also flows from the ulcers, which dries out in the form of a whitish skin in dry weather. Bacteria are spread by water droplets and persist in plant debris and seeds. Bacteriosis manifests itself intensively in the presence of water droplets on plants and at a temperature of +19 ... +24 º C.

Brown (olive) spot

It is caused by the fungus Cladosporium cucumerinum. The disease is more common in film greenhouses. Stems, leaves, but most often fruits are affected.

Small watery spots first form on the fruits, which deepen and quickly increase in size. The peel of the fruit in the affected areas cracks and a gelatinous drop appears on the surface, which quickly hardens and falls off. With high air humidity, the affected areas become covered with a grayish-green velvety coating. The spots merge and form large, irregular ulcers. When the ovaries are damaged early, they become crooked, deformed, and their growth stops.

Small ulcers with an olive-greenish coating form on the stems, petioles and veins of the leaves, especially the central ones. On the leaf blades there are rounded spots with a barely noticeable olive bloom. The spots are surrounded by a chlorotic zone. The spread and storage of infection occurs by conidia, which during the mid-vegetation period are found on plant debris and structures of cultivation structures.

Black mold

Also, on cucumber leaves in greenhouses, the pathogens of black mold, or “guardianship” (causative agent Corynespora melonis), dry mold (pathogen Alternaria cucurbitae), macrosporiosis (pathogen Macrosporium cucumerinum) develop, which form spots, respectively: light brown, of different shapes, later merge, necrotize, small, dry, barely convex with a black coating, small at first, later enlarge and become zonal.

All of them cause premature death of leaves. They also have a negative impact on productivity. For their development, their pathogens require an increased hydrothermal regime.

Protective measures

The system of protective measures in greenhouses when growing cucumbers is based on the biological characteristics of pathogens that develop in a specific artificially created climate, using all methods. The vast majority of pathogens persist during the mid-growing season on plant residues in the soil, on cultivation structures, as well as in infected seed material. During the growing season, pathogens of infectious diseases form sporulations, through which the disease is transmitted from sick to healthy plants. So, the system for protecting cucumbers in greenhouses must include measures aimed at destroying sources of infection, preventing primary infection and limiting the development of the disease.

Protective measures are also carried out taking into account the previous crop, because pathogens that are harmful to the subsequent crop are formed on it.

After the last harvest, the cultivation premises are repaired and first disinfected to destroy pathogens that have accumulated on the plants. Carbation and bleach are added to the soil. Disinfection of plant residues, soil surfaces, artificial substrates, frames, racks, walls, as well as containers and tools should be carried out wet with formaldehyde or sprayed and coated with bleach. It is also recommended to use a mixture of thiophos and copper sulfate for spraying. Insecticides and acaricides are added against pests.

After the first disinfection, all plant residues and debris are carefully removed from the greenhouses and burned. Next, a second disinfection is carried out with the same preparations as the first time, or the greenhouses are fumigated with sulfur dioxide. After this, the soil is sterilized by thermal or chemical means, observing processing technologies, application regulations, safety precautions, etc.

In this way, the causative agents of root rot, infectious wilt, rot, ascochyta blight, powdery mildew, downy mildew, anthracnose, etc. are destroyed. 25-30 days after thermal or chemical disinfection of the soil, seedlings can be planted. For its cultivation, infection-free soil is used.

Pre-sowing preparation of cucumber seeds is of great importance. The seeds are heated in a thermostat at a temperature of 56-80 º C for 8-12 hours, calibrated in a solution of table salt and disinfected in a 1% solution of potassium permanganate for 30 minutes. Next, the seeds are washed with water, dried in air and disinfected with disinfectants, which are recommended by the List of pesticides for use in Ukraine (2012), with the active ingredients metalaxyl and boscalid (Apron 35% z.p., Intur Profi, TN). Agat 25 K, PA (inactivated bacteria Pseudomonas aureofaciens) is allowed for biological products.

Another method is two-phase thermal disinfection: dry seeds are heated at a temperature of +50 ... +52 º C with an exposure of 48 hours and +78 ... +80 º C for 24 hours. Before sowing, it is soaked in water for 12-24 hours, and then germinated at a temperature of +25 ... +28 º C in a humid environment. This measure is effective against pathogens that are stored in or on seeds - wilt and fusarium root rot, downy mildew, anthracnose, bacteriosis, ascochyta blight, viruses.

Also, against root rot of cucumber, seeds can be treated with biological products - agatabo pseudobacterin (Pseudomonas aureofaciens), BSP or biopolicide (Paenibacillus polymyxa P), trichodermin (Trichoderma lignorum).

In order to increase the resistance of plants to pathogens, especially in the early stages of cucumber organogenesis - root and basal rot, wilt, ascochyta, white and gray rot, etc. seedlings are fed with mineral fertilizers (urea, potassium chloride, magnesium sulfate) and microelements (boron, manganese, copper).

When growing cucumbers indoors, you must carefully adhere to the correct agricultural technology: maintain the air temperature not lower than +18 ... +20 ° C at night and not higher than +26 ° C during the day; relative humidity according to 80-85% and 75-80%; watering with water heated to +22 ... +24 º C. It is necessary to avoid sharp fluctuations between day and night temperatures, to prevent condensation and drafts. In sunny weather, glass greenhouses must be whitened with chalk in time. These agrotechnical measures inhibit the development of pathogens. When a cucumber is affected by olive, brown spot, anthracnose, ascochyta, white and gray rot, the air humidity in the greenhouse is reduced to 70%, active ventilation is carried out, watering is stopped, and individual parts of the plants are removed.

When root and basal rots appear, the seedlings are removed, and Previkur 607SL, v.r.k., is used on adult plants. – The soil is watered with a 0.15% solution, and the plants are sprayed with a 0.2% solution.

Against powdery mildew on cucumber in greenhouses, from the beginning of its discovery, it is allowed to use sulfur-based fungicides (Tiovit Jet), derivatives of tiuredobenzoliv with the active ingredient methyl thiophanate (Topsin M 70% sp. - 0.1% per suspension), derivatives of benziimidazole with the active ingredient benomyl (Benlat 50% s.e.) Triazole derivatives with the active ingredients triadimefon (Bayleton - 0.01% suspension) and penconazole (Topaz 10% s.e.).

Against downy mildew of cucumber, the List of Pesticides Permitted for Use in Ukraine (2012) includes fungicides whose active ingredients are dimethomorph and mancozeb (Acrobat MC 69%, sp.) fosetyl aluminum (Alyette 80%, pp. ) cymoxanil and copper oxychloride (Kurzat R 44, sp.; Ordan) fluopicolide and propamocarb hydrochloride (Infinito 61 SC) mancozeb and metalaxyl (Metamil MC, 68% w.p. and Ridomil MC Gold 68% w.p.) ; aluminum phosphites and phosphoric acid (Fital)

Drugs such as Alpha Doctor, KS and Quadris 250 SC (active ingredient azoxystrobin), effective against pathogens of powdery mildew, downy mildew, ascochyta blight and anthracnose; Cabrio Duo, EC (active ingredients pyraclostrobin and dimethomorph) – against the pathogens of powdery mildew, downy mildew and Alternaria; Luna Experience 400 SC (active ingredients tebuconazole and fluopyram) – against the pathogens of powdery mildew, anthracnose, alternaria and ascochyta; Honey Extra (active ingredient copper chloroxide) – against pathogens of downy mildew, anthracnose and bacteriosis. If necessary, treatments are repeated after 10-14 days. Below is an interesting video on the topic.

Scientific institutions are developing systems for protecting cucumbers in greenhouses with the predominant use of biological preparations. Biological preparations with fungicidal action are created based on bacteria of the genera Pseudomonas, Bacillus, fungi of the genera Trichoderma, Ampelomyces, Chaetomium, Coniothyrium, etc. Technologies for their use are being developed for the prevention and treatment of cucumber against common and harmful diseases.

Nina Pletnikova, Ph.D. agricultural sciences