Pests of cucumbers with photos and their treatment. Ways to fight
Causes of diseases on cucumbers
- plant remains of the last year. It is necessary to observe the crop rotation or steam the greenhouse soil;
- wild weeds that are vectors. They must be destroyed;
- infection inside and on the surface of seeds. It is necessary to warm up the seeds and treat them with fungicides before sowing;
- rains containing spores of a pathogenic disease, therefore it is better to grow in a film or glass greenhouse;
- seedlings infected nearby. They must be removed immediately and the soil must be disinfected.
Having studied the causes of diseases, let's move on to their description and control measures.
Cucumber viral diseases
A feature of these diseases is the presence of a living host-carrier. Viruses do not live long outdoors, but they can be easily transferred during harvest or forming with sap. It differs from other diseases in that the color of the leaves of individual areas changes in the form of a mosaic. At the same time, the leaf is deformed, wrinkled, and this manifestation is asymmetric, which distinguishes them from the signs of an overabundance of growth stimulants, which appear almost the same, but symmetrically. Consider the manifestation of the most common viral diseases.
Viral diseases are often seed-borne. The virus can be neutralized by warming dry seeds before sowing at a temperature of + 50 degrees for three days, and then a day at +70 degrees. If a plant sick with a virus is noticed, then it is immediately uprooted, and the soil is watered with boiling water. To exclude infestation from weeds, they are destroyed around the cucumber planting at a distance of at least 10 m.
Bacterial diseases of cucumbers
Angular leaf spot... It is caused by bacteria that penetrate the stomata of leaves or damage to the integumentary tissues. Other plants of the pumpkin family are also affected, which can be reserves of infection. Basically, the source of infection is seeds, in which bacteria can persist for about 2 years, and in the soil they quickly die. The incubation period is up to 10 days. Bacteria are transferred by air masses and hands, when caring for the beds. The manifestation of the disease begins with the lower leaves, angular brown spots are formed on the leaves of the cucumbers from the upper part and an oily yellowish bloom from the lower part of the leaf. Affected fruits have small, round ulcers. The leaves gradually dry out, the planting completely dies.
To combat bacterial disease, antibiotics are necessary, but there are no drugs specially developed for this. A single use of penicillin at a concentration of 1 million units is possible. for 10 liters of water when the first signs of the disease appear.
Gray rot. Caused by bacteria under cool conditions. All aerial parts are affected, brown areas and a thick gray coating appear on cucumbers. The disease will spread rather quickly. The period from infection to the onset of symptoms is 3-5 days.
To cope with the disease, watering is stopped, the greenhouse is well ventilated, the affected parts are smeared with a pasty mass made from the drug Rovral or Euparen multi.
Fungal diseases of cucumbers and their treatment
The most common and harmful diseases are caused by spore-bearing imperfect fungi. Cucumber has very delicate integumentary tissues, so it is easily affected by various types of this infection. To prevent contamination from plant debris, cucumber must not be grown in one place for two consecutive years.
Root rot... Cause fungi, which are ubiquitous in the soil, feeding on inanimate plant debris, healthy seedlings are not affected. They arise only at the moment of weakening of plants, mainly due to the low temperature of the soil below +16 degrees. The root loses live root hairs, becomes covered with a brown coating, leaves and stem wither.
When buying seeds, you can see that some of them have already been processed and painted in a bright signal color. This is done to eliminate some of the infection on the surface of the seed, and to give a noticeable color, which makes sowing easier as it becomes more visible. Usually covered with a coating containing the fungicide Thiram, which suppresses fungi that cause root rot.
If the disease begins to manifest itself, then it is necessary to increase the temperature of the soil, pouring it with warm water with the addition of potassium permanganate to a slightly pink color. The stems, lowering from the support, are laid on the ground and sprinkled with soil to form additional roots.
White rot or sclerotinosis. A highly infectious dangerous disease that manifests itself as white flakes with black dots on all parts of the plant. Slimy soft spots appear on them. Aerial parts wither and die within 3-5 days. There are currently no effective drugs. When this disease of cucumbers appears in the greenhouse, it is quarantined with the destruction of all plant residues and the treatment of the soil with steam or its replacement.
Anthracnose. Ascochitis. Cladosporium. These fungal diseases have similar symptoms, mainly brown spots appear on cucumbers. Affected leaf tissue crumbles and holes appear. Brown lesions appear on the fruits. The plant eventually loses its leaves and dies. Spores of these fungi overwinter on plant debris and are transferred from infected plants to healthy ones by the wind. These diseases have an incubation period and begin to manifest themselves 3-7 days from the moment of infection.
To combat diseases, it is necessary to carry out preventive treatments with one of the copper preparations: 1% Bordeaux mixture, abiga-peak, copper oxychloride. Stop using these fungicides 30 days before harvest.
Powdery mildew. A fungal disease that manifests itself in high humidity, often after prolonged rainfall. The disease manifests itself 3-5 days after infection with spores. A white bloom appears on cucumbers only on the upper part of the leaves. They gradually shrivel and then dry out, the seedlings stop growing and die.
To combat this disease, preparations containing sulfur are used, for example, Quadris or Colloidal sulfur. Processing is carried out prophylactically every 2 weeks and stopped 14 days before harvest.
Peronosporosis or downy mildew of cucumbers. The most harmful disease, since the defeat is lightning fast and there are no sufficiently effective means of struggle. The spores of this fungus have flagella that pierce even thin aluminum foil. For infection, drip-liquid moisture is required. Optimal conditions for infection are +18 degrees and 100% relative humidity. Peronosporosis of cucumbers appears as a whitish bloom with a purple tinge on both sides of the leaf, which is a distinctive feature of powdery mildew. Fruits become incompletely colored and tasteless. The leaves turn brown quickly, crops completely die.
Until recently, only early maturing cucumbers could be grown. Currently, the cultivation of resistant or tolerant varieties allows you to get a harvest even in the open field. In greenhouses, cucumbers are less susceptible to disease during preventive treatment with copper preparations and the alternation of preparations of various chemical groups, for example, Strobi, Ridomil Gold, Bravo. Treatments are stopped 30 days before harvest.
We hope that the information presented in the article will allow you to avoid many diseases of cucumbers and get a high yield.
grounde.ru
Cucumbers are affected by diseases or pests, what should I do?
Have you noticed that the leaves of cucumbers turn yellow, shrivel, wither one by one? Most likely, the plants were attacked by pests or were affected by some kind of disease. Various pests, bacterial, viral and fungal diseases of cucumbers in a greenhouse or outdoors are most often the result of improper plant care.
For example, from excessive moisture on the leaves, stems and fruits of cucumbers, powdery mildew, anthracnose, white rot may appear, and root rot will develop on the roots. At low humidity, spider mites multiply rapidly. From weeds to cucumbers, melon aphids are transferred. And if you do not change the soil before sowing seeds, various fungi and viruses will overwinter in plant remains and then the fight against diseases of cucumbers will not give any result.
Most problems can be avoided by following basic rules for growing cucumbers:
- carry out disinfecting treatment of seeds before sowing;
- observe crop rotation with other vegetable crops and change the soil;
- maintain an optimal humidity level (in the greenhouse about 80%), from time to time airing the room with plants;
- avoid sudden changes in daily temperatures;
- pour warm water;
- weed weeds as they appear;
- feed the cucumbers with fertilizers.
The most common pests of cucumbers
When growing cucumbers in greenhouses and greenhouses, you can often observe how white or light yellow dots appear on the leaves, and then the leaves are completely covered with spots and, turning yellow, dry out. There is no doubt - he settled on your plants spider mite... A tick on cucumbers is quite common, it braids the leaves from below with a barely noticeable cobweb, pierces the skin of the leaf and drinks the juice of the plants. It is difficult to notice him with the naked eye, since his body is only half a millimeter in size.
photo of greenhouse whitefly
To combat spider mites, collect the affected leaves in a bucket and burn them or bury them deeper in the ground. During the growing season, it is necessary to carry out several treatments of plants with different insecticides ("Fosbecid", "Agravertin", "Fitoferm", etc.). You can spray plants with "Karbofos", especially pay attention to the lower part of the leaves. To prevent spider mites from appearing on cucumbers, it is recommended to plant seedlings early and constantly destroy the weeds around the cucumbers. Video about diseases and pests of cucumbers
Cucumbers, along with pumpkins and zucchini, amazes melon aphid- a small insect (up to 2 mm), with a color from yellow to dark green. Aphids, like ticks, settle on the lower part of the leaves, as well as on flowers, ovaries and shoots, causing twisting and drying of parts of the plant. Since aphids and their larvae overwinter in plant debris, moving from weeds to vegetable crops, first of all, it is necessary to ensure timely weed control. You can also collect ladybugs hibernating under rotten foliage and put them in a greenhouse.
spider mite photo
Also found on cucumbers and tomatoes greenhouse whitefly, sucking juice from the leaves, thereby damaging them. On the sugary secretions left by the whitefly, sooty mushrooms are formed, as a result, the leaves turn black and dry out. Regular weed control and covering the vents and doors with gauze in one layer will help prevent the appearance of whitefly. Spray the affected plants with clean water, washing additionally the lower part of the leaves, where a large amount of whitefly accumulates most often. After flushing the pests, loosen the soil a couple of centimeters.
Diseases of cucumbers, their manifestation and methods of struggle
Cucumbers are most often subject to fungal diseases, which can persist from year to year in plant debris and quickly spread to plants when the air humidity rises. Therefore, for the prevention of diseases, it is especially important to observe all the above rules for caring for cucumbers. Video about protection against diseases and pests of cucumbers
The most common diseases of cucumbers:
- Gray rot... Large gray or brown spots form in the axils of the leaves and in the places of branching on the stem, and on the fruits - a gray fluffy bloom. Many male flowers appear, barren flowers rot, thus affecting healthy stems. The affected areas are sprinkled with ash, the plants are ventilated, watering is temporarily suspended. If the disease progresses, the damaged areas are removed and burned. It is recommended to grow self-pollinated cucumber varieties and avoid thickened sowing.
- Powdery mildew... Appears on leaves and stems in the form of whitish or reddish spots. The affected parts of the plant are powdered with wood ash or removed altogether. You can spray the cucumbers on all sides with a solution of mullein or colloidal sulfur.
- White rot... Roots, leaves, petioles, stems and fruits are covered with white mycelium, become slimy, and rot. Remove damaged parts or sprinkle with fluffy lime. The spread of the disease is facilitated by excessive moisture in the soil and air, poor ventilation, and thickening of the plantings.
- Root rot... At the beginning of fruiting, separate brown spots are formed near the roots of cucumbers, which subsequently merge into one large spot. As a result, the stem rots, the roots die off. The disease develops intensively with temperature extremes and high humidity. Sore spots should be dried, powdered with ash or chalk, water only the soil around the plant. The dead plants must be dug up together with a lump of earth and burned, and the hole must be treated with copper sulfate. To prevent root rot, it is necessary to disinfect the soil.
- Ordinary mosaic... Light green and dark green spots that appear on the leaves, making it wrinkle. Mosaic discolouration and bumps can also appear on the fruit. The infection spreads through weeds and infected seeds, so only treated seeds should be used for sowing, preferably purchased ones, and not your own. Remove diseased plants, and disinfect the inventory in a solution of bleach or potassium permanganate.
- Olive spot of cucumbers... Brown ulcers appear on the fruits, from which liquid is released. Disease occurs as a result of watering the plant with completely cold water, from drafts and due to high humidity. The causative agents of the disease persist in the affected fruits and plant waste. If an olive spot is found, stop watering cucumbers for 5 days, spray the plants and fruits with Oxyhom or Bordeaux liquid (1% solution). It is recommended to choose the varieties that are most resistant to this disease.
You can see what the most common diseases of cucumbers look like in pictures by opening the tab with photos. Identifying symptoms in a timely manner will help prevent disease or pests from spreading to healthy plants and preserve your harvest.
orchardo.ru
Diseases of cucumbers photo, description and treatment in a greenhouse, in the open field
Growing cucumbers is quite troublesome. The following conditions must be met:
- selection of a suitable site;
- preparation of seedlings and seeds;
- careful care during the period of active growth.
As a result, all the work can be in vain if the cucumbers are attacked by pests or get sick. In this case, the entire crop can be destroyed. That is why it is always necessary to apply preventive measures when growing.
Diseases of cucumbers photos and their treatment: prevention
Long before planting, you should think about how to treat cucumbers from diseases and pest infestations, since most diseases are not cured and are easier to prevent.
Professional gardeners recommend following some planting and growing rules to avoid problems and additional care afterwards. It is with these simple tips that one should begin to consider the diseases of cucumbers and the fight against them will not seem scary and endless.
- So that the diseases of the cucumbers whose photos are in the article do not interfere with rooting and growth, it is worth giving preference to resistant varieties.
- High-quality and disinfected seeds are suitable for planting. They should be bought from trusted manufacturers or procured on their own, as well as additionally treated with disinfectants (Grandsil and Grandsil Ultra).
- Seeds are sown exclusively in heated soil. At a depth of 10 cm, the temperature should be at least 12 degrees Celsius.
- The soil needs to be loosened and properly fertilized.
- The remnants of last year's plants must be removed from the beds, since insect larvae and viral bacteria can be found in them.
- It is important to observe the turnover of crops and plantings (it should be alternated with legumes), weed cucumbers regularly, eliminate unhealthy plants in a timely manner, and treat pests.
- Do not forget that diseases of cucumbers in a greenhouse and their treatment require a thorough approach. In greenhouses, as well as in open gardens, the frequency and rate of fertilization are of great importance. It is not recommended to exceed the composition of the elements: urea (6-12 g), superphosphate (about 10 g), potassium chloride (about 8 g) and ammonium nitrate (no more than 6-7 g) per 10 liters of water.
Diseases of cucumbers photos of leaves and fruits: treatment and prevention
The most dangerous for plants is the treatment with the wrong means and fertilization with the wrongly chosen preparations, therefore it is important to determine the disease by its external signs and to know the preventive and therapeutic methods.
White rot
White rot of cucumbers appears on the stem
Most often, cucumbers are affected by leaf diseases, covering over time their shoots, antennae, peduncles and ovary. With white rot, the plants are completely covered with mucus and bloom. The infection develops especially quickly in greenhouses with thickened plantings, high humidity and stagnant air.
To get rid of white rot, you need constant temperature control, thinning of plantings and timely weeding. The affected parts of the bushes should be carefully cut off, and the wounds should be powdered with ash or slaked lime. With this disease of cucumbers in the greenhouse or in the beds, disinfection of the soil is necessary (with 1-2% manganese solution or nettle infusion), and with severe infection, its complete replacement by 10-15 cm in depth. You should also spray the crops with a special solution (10 liters of water, 2 g of copper sulfate and 10 g of urea).
Root rot
The consequences of root rot
The disease is dangerous for the measles system, because with it part of the rhizome dies off, and the stem itself becomes rotten, and the plant dies just before our eyes. Root rot is caused by cold weather, heavy and too wet soil and poor quality seeds. Almost all diseases of cucumbers of an infectious nature are dangerous because the pathogen can be for a long time in the beds, in greenhouses or uncleaned plant remains.
If you notice that root rot of cucumbers has begun, treatment is carried out by mulching the bushes with clean sand, peat mixture, chalk (limestone) or sawdust. Already infected - should be mercilessly cut and disinfected with dry bleach in a volume of up to 200 g per sq.m. It is advisable to use warm irrigation water.
Powdery mildew
Powdery mildew of cucumbers
It is this disease of cucumbers that is considered the most common. Its signs are noticeable not only on the leaves (small white spots, gradually covering the entire surface), but also on the stems with petioles. The disease stains the whips completely brown, they dry out and fall off.
The reasons for the appearance of powdery mildew are almost the same as those that cause other diseases of cucumbers with photos - temperature fluctuations, excessive humidity, excess weeds and neglect of plantations. Cold irrigation water, drafts and strong winds can also lead to its development.
If powdery mildew appears on cucumbers, measures to combat it will consist in pruning the affected parts of the stem and disinfecting the soil. Recommended processing:
- ground sulfur up to 30 g for every 10 sq.m. vegetable garden;
- solution of 3% colloidal sulfur up to 30 g per 10 l of liquid.
Deep digging of beds, scrupulous destruction of plant residues, systematic application of potassium fertilizers will also not be superfluous for prevention.
Peronosporosis
Greenish bloom and yellow spots are signs of peronosporia
The enemy destroying entire fields appears with a greenish bloom and yellow spots on the upper part of the foliage. It tends to spread over the entire surface of cucumbers and infect plantings growing in the immediate vicinity.
Downy mildew, also called peronosporosis, can spread rapidly due to frequent fogs, a lot of dew, too cool watering and temperature changes.
Peronosporosis of cucumbers, the treatment of which experts recommend using a milk-iodine solution (10 drops per 10 l) or urea (1 g per 1 l), will not interfere with obtaining beautiful ripe fruits. The main thing is not to forget about the disinfection of seeds, warming up the soil and mandatory feeding.
Anthracnose
Anthracnose is expressed in yellow-brown spots
Yellow-brown spotting on foliage and pink bloom on the rest of the bushes is most often the result of anthracnose, which develops to a greater extent with excess moisture. At first, barely noticeable mucus appears on the culture, however, in places of its concentration, small ulcers are almost always formed, which lead to the death of the bush.
The virus is transmitted with the seed and infected plants remaining in the ground, and rainy weather and humidity create favorable conditions for the spread of pathogenic bacteria.
To prevent the disease of cucumbers in the greenhouse and on the plots, it is necessary to sow only proven seeds in sufficiently heated and treated soil. It is better to purchase seed material from friends, from official agro-technical companies, or procure it yourself. With already proven anthracnose, the treatment of cucumbers from diseases with folk remedies helps:
- a mixture of milk of lime and copper sulfate;
- bleach solution (up to 40 g per 10 l of water).
Cladosporium
Dark brown and olive spots are a sign of cladosporium
Many of the diseases of cucumbers considered and their treatment concerned damage to the foliage and stem, from which the plant itself died. Cladosporia primarily affects the fruit itself. Small, but numerous spots of a watery type appear, which quickly grow and harden, which leads to cracking of the skin of the vegetable and its death.
This ailment is also called olive spot, which can spread directly through the air, infecting areas with cucumbers during irrigation or during rains.
Preventive treatment of cucumbers for diseases is carried out with a 15% suspension of Bordeaux mixture. However, the problem may not be completely resolved. If the remedies do not help, and contaminated cucumbers constantly appear, airborne diseases are prevented by reducing humidity and choosing the most resistant varieties.
Diseases of cucumbers photo leaves treatment for fusarium
Diseases of cucumbers photo leaves treatment for fusarium
This disease can be massive or spread by foci in vegetable gardens and greenhouses without proper heating. Fungal diseases of cucumbers affect plantings at different points in their growth. The problem with fusarium is that infection may not manifest itself externally until the plants enter the fruiting phase, when they begin to droop and die.
Fusarium wilting of a cucumber, the treatment of which does not bring the desired results, must be prevented even at the planting stage. You can avoid infection:
- seed dressing;
- maintaining the required humidity and temperature in greenhouses;
- thorough disinfection of the earth and processing of the material with Trichodermin (5 g per 1 kg) will not interfere.
Pests of cucumbers with photos and their treatment. Ways to fight
Most infections are carried by insects, so it is important to monitor their spread and take preventive measures in time.
Melon aphid
Cucumber pests - melon aphid
Small pests of cucumbers, mercilessly destroying ovaries, flowers and leaves, are far from a wonder for experienced gardeners, especially in rainy seasons. To destroy them, you need to take care of the correct turnover of plantings on the site, dig up and disinfect the soil and carefully get rid of weeds.
When the aphid has already attacked the plantings, spraying them with a fermented herbal infusion (1 kg is infused in 10 liters of liquid during the day) or an ash suspension (10 liters of water, 50 g of soap shavings, 200 g of ash) will help.
Spider mite
Spider mites breed in hot weather
It settles down on the lower sides of the leaves and, entwining them with a thin web, feeds on sap, which can cause significant damage to all plantations. Hot weather is ideal for mites to breed.
For prevention, you should properly irrigate the land. Moisture becomes favorable for the spread of most insects, but extremely dry soil is suitable for the tick. Garlic or onion infusions (10 liters of water and 200 g of husks) will help to cope with the destruction of colonies. It is necessary to spray the bushes 4 times a season.
Whitefly
Gluttonous Whitefly Larvae
The microscopic insect moves and lives no more than a day in the air, but manages to lay voracious larvae on the deciduous part of the cucumber. They suck the juices from the crop, which leads to the development of a sooty fungus.
It is difficult to neutralize the whitefly due to its fertility. The methods of breeding insects themselves are not so complicated, it is enough to regularly wash off the larvae from the bushes and loosen the soil, followed by the introduction of peat or humus into it. Spraying with Inta-Vir will help get rid of the colonies already gathered on the leaves.
Ants
Ants breed aphids on cucumber foliage
They are pests that dig millions of underground tunnels and contribute to the appearance of aphids on leaves and stems.
It is easy to deal with them: with the help of sweet baits (syrup) and dusting the earth with ash or lime. Noticing the nests of ants, you can pour boiling water over them, dig up or pour plenty of kerosene (waste oil is also used).
Slugs
Slugs mainly damage the leaves, but they can also feast on the fruits.
Insects are afraid of daylight, so they choose to eat fresh herbs and fruit pulp at night. Dark droppings and the characteristic shiny slug marks also do not improve the quality of the crop.
Regular digging of plots and pollination with ash or chalk will help to destroy pests. You can also try to lay out special shelters in which the slugs will find refuge for themselves, and collect them during the day. It is also recommended to treat cucumber beds with Metaldehyde.
Outcome
Treatment of various diseases of cucumbers and pest control is not an easy process, but a serious approach to all measures and timely prevention will significantly simplify it and get an excellent harvest as a result.
In most cases, infestations can be avoided by observing safety precautions with planting, proper fertilization and watering. Follow the recommendations of professional gardeners and reap a rich harvest.
vsadu.ru
Diseases of cucumbers in the greenhouse: description of photo video
The conditions that are created in closed ground when growing vegetable plants, in particular, long-term use of the soil, a limited set of crops, an artificial microclimate, contribute to the massive development of diseases.
The most common infectious diseases of cucumber in greenhouses are root and root rot, wilting, white and gray rot, ascochitis, powdery mildew, downy mildew, bacteriosis, brown spot, olive spot, anthracnose, black mold, alternaria, etc.
We will now consider these and some other diseases in detail.
Root and root rot
They affect seedlings, seedlings and adult cucumber plants. At first, small brown streaks and spots form on the roots, which grow and merge. The roots of seedlings and seedlings rot, die off. Affected seedlings lodge.
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 ...
An interception with or without decay may form on the underside of the stem. On the cross-section of the stems of the affected plants, you can see the browning of the vessels. Stems are delayed in growth, wither. The leaves of seedlings are often deformed with small brown spots. On the leaves of adult plants, interveinal chlorosis and magnesium starvation necrosis can be found.
Root rot is a consequence of the action of a complex of pathogenic fungi with Fusarium, Pythium, Rhizoctonia, Phytophthora, Phomopsis. All pathogens remain in the soil. Fusarium root rot pathogen may persist in cucumber seeds.
Sowing of seeds in cold waterlogged soil, watering with cold water, a sharp drop in soil temperature (below +16 º С) or overheating (above +28 º С), excess nitrogen, excessive organic background contribute to the development of the disease. Cucumber root rot can also be non-infectious. In this case, the vessels turn brown at the roots, the tissues exfoliate, and cylindrical cavities form around the vascular bundle.
Withering cucumber
This problem is caused by the fungi Fusarium oxysporum, Verticillium albo-atrum and V. dahliae, which harm during the entire growing season. Pathogens enter the vessels of the plant from the soil through the roots, develop there, clog the vessels and release toxins. On the stems of the cucumber near the ground, the vessels become silvery-white, and the browning of the conducting system is clearly visible on the cross section. Sometimes a white or pinkish bloom of pathogen sporulation appears on the stems. The lower leaves wither during the daytime, and at night their turgor resumes. Later, the leaves become chlorotic and die off. Sick plants grow poorly, their fruits are small, with low palatability.
Also, wilting of plants can be caused by underdeveloped roots of cucumber, when the seedlings were planted in dense soil, which mechanically squeezes the root system, and water with nutrients cannot enter the plant.
The causative agents of the infectious wilting of cucumber can persist for a long time in the soil, and the fusarium can also persist in the seeds.
White rot
Its causative agent is Sclerotinia sclerotiorum (Whetzelinia sclerotiorum), a polyphagous fungus that infects a wide range of plants, both cultivated and wild. Develops on vegetative stems, leaves and cucumber fruits.
At the base of the stems, the tissues become wet, covered with white, like cotton wool, with a bloom of mycelium, and become wet. The stem dries up, the leaves sag. In addition to the root part, white rot can appear higher, especially in the places of branching. When plaque is compacted, black sclerotia may form. Diseased fruits look like boiled ones and are also covered with bloom.
The development of the disease is facilitated by thickened crops, high air humidity, insufficient ventilation, 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 aboveground organs - stems, leaves, flowers, ovaries, fruits.
In places of lesion, 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.
The persistence of infection in the off-season occurs in the soil and on the structures of greenhouses.
Ascochitosis
Ascochytosis (Ascochyta melonis) affects seedlings and adult plants. On seedlings in the root part of the stem, watery, wet spots with numerous black dots - pycnidia are formed. In the future, an interception is formed.
In adult plants, stems, petioled leaves and fruits are affected. The stem form is manifested in the places where the petioles are attached. Sore areas of the stems become dry and almost black due to numerous pycnidia. Around these areas, parts of the stem are grayish-white, dry, cracked, and loosened.
Large, at first yellow-brown, vague spots are formed on the leaves, which later brighten, become covered with black pycnidia, merge and cover a significant part of the leaf blade, and sometimes more. Diseased leaves, starting from the bottom, dries up. When fruits are damaged, black pycnidia also form on their surface, especially at the point of attachment to the stalk. The fruits become, as it were, boiled, but do not soften, but dry out. The pathogen spreads during the growing season with pycnospores, which are spread by splashes, drops, streams of water and air currents. Infection persists on plant debris, and seed infection is also possible.
The development of diseases of cucumbers is facilitated by the increased humidity of the air and the weakened state of the plants.
Downy mildew
The causative agent Pseudoperonospora cubensis appears on cucumber leaves of different ages. On the upper part of the leaf blade, yellow-green, rounded, angular or indefinite spots are formed. Below, under the palm trees, in damp weather, a gray bloom is formed, consisting of conidial sporulation of the fungus. Diseased leaves become brown, brittle, they curl and dry out. With a strong degree of damage, the plants die. For the development of the fungus, drip moisture, air humidity 90-100% and temperature +16 ... +20 º С.
The infection persists in plant debris and seeds.
Cucumber powdery mildew
Its pathogens are Sphaerotheca fuliginea Erysiphe cichoracearum. Plants are affected starting from the stairs. Cotyledonous leaves and leaves and petioles of adult plants are first covered with a thin white or pink-gray bloom, which is a conidial sporulation of pathogens. Plaque is mainly located on the upper side, at first in separate spots, later - solid. Numerous small, black dots are formed on the plaque - marsupial sporulation - cleistothecia, which are not often observed in open ground. Diseased leaves turn yellow, deform, die off. Sometimes stems and fruits are covered with bloom.
In the greenhouse, the infection is introduced mainly from open ground in the fall (with an autumn-winter culture of cucumber) or at the beginning of summer (with a spring-summer culture), and also persists on plant debris.
The development of the disease becomes possible by sharp fluctuations in humidity and air temperature, drafts, lack of light and optimal temperature for the pathogen +16 ... +20 º С, wilting of plants. More often pockets of powdery mildew begin at doors, transoms, heating pipes.
Anthracnose (copperhead)
It is caused by the fungus Colletotrichum lagenarium, which develops on the cucumber during the growing season on the leaves, stems and fruits. Yellowish-brown, mostly round spots appear on the cotyledons and leaves. Tissues in places of spots are necrotic, crumble.
On the fruits, in-depth, in the form of ulcers, spots are formed - single or in groups. In wet weather, spots become covered with a pink-copper bloom, which eventually darkens and becomes black, dense. Sick fruits are bitter, rot during transportation and storage.
Stems and petioles are covered with in-depth elongated spots, on which a pink bloom of conidial sporulation of the pathogen is also formed. During the growing season, the pathogen is spread by conidia by airborne droplets. Infection persists in plant debris and infected seeds.
Favorable conditions for the development of the cucumber anthracnose pathogen are high air humidity - about 90% and high air temperature - +22 ... +27 º С.
Bacteriosis (angular spotting)
The disease is caused by the bacterium Pseudomonas lachrymans. The first signs can be found on the cotyledons when light brown small spots or ulcers appear. On the leaves, angular, veined spots are formed. At first they seem to be soaked in water or oily, later they turn brown. In wet weather, on the underside of the leaf under the spots, a bacterial exudate appears as a cloudy drop. In the future, diseased tissues dry out, die off and fall out, forming holes.
On the stems and petioles there are small spots that deepen over time. There are also ulcers on the fruits, but they are deep, as if nailed by birds. Exudate also flows from the ulcers, which dries up in dry weather in the form of a whitish skin. The bacteria are spread by droplets of water, and remain in plant debris and seeds. Bacteriosis is intensely manifested in the presence of water droplets on plants and a temperature of +19 ... +24 º С.
Brown (olive) spot
It is caused by the fungus Cladosporium cucumerinum. The disease is more common in plastic greenhouses. Stems, leaves, but most often fruits are affected.
At first, small watery spots form on the fruits, which deepen and quickly increase in size. The peel of the fruit cracks at the lesions and a gelatinous drop emerges on the surface, which quickly hardens and falls off. With increased air humidity, the lesion sites are covered with a grayish-green velvet bloom. The spots coalesce and form large, irregular ulcers. With early damage to the ovaries, they become crooked, deformed, and their growth stops.
On the stems, petioles and veins of the leaves, especially the central ones, small ulcers form with an olive-greenish bloom. On the leaf blades there are rounded spots with a barely noticeable olive bloom. The spots are surrounded by a chlorous zone. The spread and storage of infection occurs by conidia, which during the inter-vegetation period are on plant debris and structures of cultivation structures.
Black mold
Also on the leaves of cucumber in a closed ground, pathogens of black mold, or "guardianship" (pathogen Corynespora melonis), dry (pathogen Alternaria cucurbitae), macrosporia (pathogen Macrosporium cucumerinum) develop, which form spots, respectively: light brown, of various shapes, later merge, necrotic, small, dry, barely convex with a black bloom, at first small, then increase and become zonal.
All of them cause premature death of leaves. They also negatively affect the yield. For their development, their pathogens require an increased hydrothermal regime.
Protective measures
The system of protective measures in closed ground when growing cucumber is based on the biological characteristics of pathogens that develop in a specific artificially created climate using all methods. The overwhelming majority of pathogens persist during the inter-growing season on plant residues in the soil, on cultivation facilities, and also in infected seed material. During the growing season, pathogens of infectious diseases form sporulation, by which the disease is transmitted from a sick plant to a healthy plant. So, in the protection system of a cucumber in greenhouses, there should be measures aimed at destroying sources of infection, preventing primary infection and limiting the development of the disease.
Protective measures are also performed taking into account the previous culture, because pathogens harmful to the subsequent culture are formed on it.
After the last harvest, the repair and the first disinfection of the cultivation premises are carried out to destroy the pathogens that have accumulated on the plants. Carbation and bleach are added to the soil. Disinfection of plant residues, soil surface, artificial substrates, frames, racks, walls, as well as containers, tools should be carried out in a wet way with formalin or sprayed and coated with bleach. It is also recommended to use a mixture of thiophos and copper sulfate for spraying. Insecticides, acaricides are added against pests.
After the first disinfection, all plant residues and debris are carefully removed from the greenhouses and burned. Then he performs the second disinfection with the same preparations as the first time, or fumigates the greenhouses with sulfur dioxide. After that, the soil is sterilized by a thermal or chemical method, observing processing technologies, application regulations, safety measures, etc.
Thus, pathogens of root rot, infectious wilting, rot, ascochitosis, powdery mildew, downy mildew, anthracnose, etc. are destroyed. Seedlings can be planted 25-30 days after thermal or chemical disinfection of the soil. For its cultivation, soil is used free of infection.
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 sodium chloride and disinfected in a 1% solution of potassium permanganate for 30 minutes. Then 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 active ingredients metalaxil and boscalid (Apron 35% salary, Intur Profi, TN). Agate 25 K, PA (inactivated bacteria Pseudomonas aureofaciens) are allowed from biological products.
Another method is two-phase thermal disinfection: dry seeds are heated at a temperature of +50… +52 º С with an exposure of 48 hours and +78… +80 º С 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 event is effective against pathogens that are stored in or on seeds - wilting and fusarium root, downy mildew, anthracnose, bacteriosis, ascochitosis, viruses.
Also, against root rot of cucumber, seeds can be treated with biological products - agatabo pseudobacterin (Pseudomonas aureofaciens), BSP or biopolycide (Paenibacillus polymyxa P), trichodermin (Trichoderma lignorum).
In order to increase plant resistance to pathogens, especially at the early stages of cucumber organogenesis - root and root rot, wilting, ascochitosis, white and gray rot, etc. seedlings are fed with mineral fertilizers (urea, potassium chloride, magnesium sulfate) and microelements (boron, manganese, copper).
When growing a cucumber in a closed ground, it is necessary to carefully adhere to the correct agricultural techniques: maintain the air temperature not lower than +18 ... +20 ° С at night and not higher than +26 ° С during the day; relative humidity according to 80-85% and 75-80%; watering with water heated to +22… +24 º С. It is necessary to avoid sharp fluctuations between day and night temperatures, to prevent condensation and drafts. In sunny weather, glass greenhouses should be whitened with chalk on time. These agrotechnical measures inhibit the development of pathogens. When a cucumber is affected by olive, brown spot anthracnose, ascochitosis, 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 root rot appears, the seedlings are removed, and on adult plants, Previkur 607SL is used. - The soil is watered with a 0.15% solution, and the plants are sprayed with a 0.2% solution.
Against powdery mildew on cucumbers in greenhouses, from the beginning of its detection, it is allowed to use sulfur-based fungicides (Tiovit Jet), thiureobenzene derivatives with the active ingredient methyl thiophanate (Topsin M 70% sp - 0.1% per suspension), benzimidazole derivatives with the active ingredient benomyl (Benlate 50% d.p.) Triazole derivatives with the active ingredients triadimefon (Baylon - 0.01% suspension) and penconazole (Topaz 10% ae).
Against downy mildew of cucumber, the List of Pesticides Permitted for Use in Ukraine (2012) contains fungicides, the active ingredients of which are dimethomorph and mancozeb (Acrobat MC 69%, d.p.) fosetyl aluminum (Allett 80%, d.p. ) cymoxanil and copper oxychloride (Kurzat R 44, s.p .; Ordan) fluopicolide and propamocarb hydrochloride (Infinito 61 SC) mancozeb and metalaxil (Metamil MC, 68% salary and Ridomil MC Gold 68% s.p.) ; aluminum phosphites and phosphoric acid (Fital)
Such drugs as Alfa Vrach, KS and Quadris 250 SC (active ingredient azoxystrobin), effective against pathogens of powdery mildew, downy mildew, ascochitosis and anthracnose; Cabrio Duo, EC (active ingredients pyraclostrobin and dimethomorph) - against pathogens of powdery mildew, downy mildew and Alternaria; Luna Experiences 400 SC (active ingredients tebuconazole and fluopyram) - against pathogens of powdery mildew, anthracnose, alternaria and ascochitosis; honey Extra (active substance of copper chloroxide) - against pathogens of downy mildew, anthracnose and bacteriosis. If necessary, the processing is repeated after 10-14 days. Below is an interesting video on the topic.
In scientific institutions, systems for protecting cucumbers in greenhouses are being developed with the predominant use of biological preparations. Biological preparations of fungicidal action are created on the basis of bacteria of the genera Pseudomonas, Bacillus, fungi of the genera Trichoderma, Ampelomyces, Chaetomium, Coniothyrium, etc. Technologies are being developed for their use for the prevention and treatment of cucumber against common and harmful diseases.
Nina Pletnikova, Ph.D. s.-kh. sciences