by There are many signs of cucumber diseases, some of which can baffle even an experienced gardener. But if you carefully examine the bush, it will be easier to figure out how to preserve the harvest.
All cucumber diseases can be divided into several groups: fungal, bacterial and viral. Often, summer residents do not even realize that their plant is sick, because it is not easy to calculate and determine the disease. Let’s carefully examine the leaves, stems and fruits of the cucumber and try to determine together what is wrong with the plant.
Fungal diseases of cucumbers
Fungal diseases are more common in cucumber beds than others. Hot weather, high humidity, pests and mistakes in agricultural technology almost always lead to health problems in cucumbers. In the worst case, up to 50% of the crop can suffer from the diseases described below! Let’s find out what fungal disease has affected the bushes and how to treat cucumber leaves to restore their health.
When using chemicals, remember that cucumbers can only be eaten 3-4 weeks after the last treatment.
Small raised brown spots on cucumber leaves
The leaves are covered with small, slightly convex spots (up to 2 cm long) of brown color along the edges and in the middle. After a while, the spots merge, the leaf dries up and dies. There are no spots on the fruits and stems.
Diagnosis: Alternaria (dry spot) of cucumbers.
Greenhouse cucumbers, which grow at the entrance to the greenhouse and often experience temperature changes, usually suffer from alternaria. First, scattered spots appear on the lower leaves, then they merge and cover almost half of the leaf blade. The process of photosynthesis is disrupted, the formation of ovaries and fruits slows down. High humidity and temperatures within 30°C contribute to the reproduction of the fungus. The disease is quickly transmitted to other plants.
Plants in film greenhouses are affected by alternaria more often than in glass ones. The main carrier of the disease is aphid.
Control measures. At the onset of the disease, spraying with copper sulfate (20 g per 10 l of water) and fungicides (Abiga-Peak, Consento, etc.) is effective. Perform treatments every 10-14 days until the leaves acquire a healthy appearance. If you want to use biological preparations, pay attention to Trichocin, which is safe for humans and animals. It can also be used in the spring for preventive soil treatment.
White coating on cucumber leaves
The lower and upper sides of the leaves are covered with a white coating. Round spots are located all over the leaf blade, then merge and darken.
Diagnosis: powdery mildew of cucumbers.
Powdery mildew is the most common disease of garden plants. It can be found on cucumbers in greenhouses and in open ground. The white coating is easy to notice: the plant looks like it is sprinkled with flour. If no action is taken, the leaf will begin to deform, then bend outward and die. The disease spreads along the entire vine, covering the stems and petioles of the fruit. The cucumbers themselves are bitter. As a result, the plant cannot set new fruits, the harvest quickly decreases. After a while, the bush dies.
The main reason for the damage is an excess of nitrogen fertilizers and improper watering.
Control measures. After the first spots of powdery mildew on cucumbers are detected, spray the bushes with a soda solution (100 g per 10 l). You can add a little laundry soap to it so that the solution sticks better to the leaves. Perform the treatment 6 times every 7 days until the plaque disappears. For preventive treatment and in case of minor damage, use the following preparations – Alirin-B, Sporobacterin, Fitosporin-M.
Rusty spots on leaves, stems and fruits of cucumbers
Leaves, stems and fruits are covered with spots (up to 4 cm) of red color. Then holes form in their place. Greens become covered with brown ulcers and stop growing.
Diagnosis: anthracnose (copperhead) of cucumbers.
The disease affects cucumbers at all stages of development. Small brown spots can be seen already on the root collar of seedlings. But anthracnose is mainly diagnosed by spots on the leaves of adult plants. The reproduction of the fungus is facilitated by high humidity (sometimes it is enough to reduce it to save the plants), as well as uncleaned plant residues. The disease quickly spreads from one bush to another.
Control measures. To treat anthracnose, treat the beds with a 1% solution of Bordeaux mixture or a 0,4% solution of copper oxychloride. Repeat the spraying after two weeks. You can also use Abiga-Peak, OxyHOM and other fungicides.
When using any chemicals, wear gloves and a respirator. Always read the instructions for use. This will protect not only your health, but also the environmental situation on the site.
Pale spots on the edges of cucumber leaves and brown spots on the stems
The edges of the leaves become lighter and covered with pale spots, which then spread to the entire leaf blade. Brown spots are visible on the stems. The skin of the fruit darkens, and black dots are visible on it.
Diagnosis: ascochytosis (black mycosphaerella stem rot) of cucumbers.
The disease manifests itself mainly at the beginning of the growing season, when the stems are covered with whitish spots. But the damage becomes noticeable during the fruiting period. The vascular system of the plant is not affected by the infection, so the bush continues to bear fruit. But the fruits are not suitable for food, they are ulcerated on the outside, and the pulp inside decomposes. Without treatment, the plant dies completely.
Ascochytosis most often affects greenhouse cucumbers.
Control measures. Spray the plants with a 10% solution of Bordeaux mixture every 1 days. Repeat the procedure 3-4 times. You can also add urea to the solution (10 g per 10 l of water) to nourish the bushes. Powder the stems with a mixture of copper sulfate and chalk (1:1). A modern biopreparation Trichoderma Veride 471 gives a good effect.
Remove lower affected leaves to control the spread of the fungus.
Small dark brown spots on cucumber leaves, grey coating on stems and ulcers on fruits
The leaves are covered with small dark-brown spots, which over time acquire an olive-gray tint. In places where tissue dies, holes with jagged edges appear. The fruits are curved, ulcers are visible on them. The stems are covered with a gray coating and die off along with the leaves.
Diagnosis: Cladosporiosis (olive spot) of cucumbers.
In summer, young fruits, which are no longer suitable for food, are mostly affected by cladosporiosis. Stems and leaves are less likely to get sick. The development of the fungus is affected by air humidity; as soon as it exceeds the norm of 80%, the spores become active and multiply en masse. In a short time, the entire greenhouse or garden bed in the open ground can be affected.
Control measures. For treatment, you can use a 1% solution of Bordeaux mixture. A 0,3-0,4% solution of copper oxychloride will also help stop the spread of the pathogen. Spray every 10-12 days at least 3-4 times per season.
White fluffy coating on the stems and fruits of cucumber
A fluffy white coating appears on the stems and fruits, the tissues soften. The plant gradually withers and dies.
Diagnosis: white rot of cucumbers.
Greenhouse cucumbers and plants planted near lettuce and parsley are at risk. The fungus mycelium multiplies very quickly and can damage all cucumber bushes. For its development, it is enough to violate just a few rules of agricultural technology, for example, to thicken the plantings or not to remove dead parts of plants in time. It is easy to infect plants when working with dirty tools. Affected cucumbers are not suitable for food.
Greens are most likely to become infected with rot if they come into contact with diseased stems.
Control measures. Preventive measures include, first of all, soaking seeds before sowing in a solution of Baktofit, pouring the soil with a solution of Alirin-B. To improve the effect, add chalk to the preparations (1:1). To strengthen the immune system and combat white rot on cucumbers, spray the bushes with a mixture of 2 g of copper sulfate, 1 g of zinc sulfate and 10 g of urea per bucket of water.
Cucumber leaves die and stems dry up
The stems dry up and become thinner, the leaves die off. The roots are covered with brown spots.
Diagnosis: root rot of cucumbers.
It is not so easy to notice this disease. In hot hours, the lower leaves of the plants turn yellow and slightly wither, as if from a lack of moisture. Additional watering only makes matters worse, the pathogenic fungus actively multiplies, and the above-ground part of the plant becomes weaker. The roots rot, and the cucumbers grow crooked, underdeveloped and tasteless. The appearance of fungus at the beginning of the growing season can completely deprive you of the cucumber harvest!
Wilting can also occur with verticillium wilt and fusarium wilt of cucumber.
Control measures. It is very difficult to fight root rot, it is easier to prevent it. It is important to water the plants only with warm water, strictly according to the schedule, dust the lower part of the bushes with peat or chalk. If root rot does appear, use Baktofit, Previkur Energy for treatment, which will suppress the activity of the fungus.
The tops of the cucumbers are wilting
During the day, the tops of the bushes wither, but at night they come back to life. After a while, the leaves turn yellow, and the plant dries up.
Diagnosis: Fusarium wilt of cucumbers.
In a short time, the bush dies off completely. The development of the disease accelerates at low temperatures and waterlogged soil, so cucumbers in open ground are at risk. Wilting can be sluggish in nature, when the bushes bear fruit, but quickly age. The main cause of infection is infected seeds.
There is also verticillium wilt, which is favored by high greenhouse temperatures.
Control measures. For treatment, use broad-spectrum fungicides, such as Previcur Energy, Consento, etc. Water the plants with the solution 1-2 times at intervals specified by the manufacturer. Dig up and burn dead plants, disinfect the soil with Trichoplant.
Light yellow spots on the upper side of cucumber leaves and a grey-purple coating on the lower side
The leaves become covered with light yellow spots, darken and die. A grey-violet coating appears on their lower part.
Diagnosis: downy mildew of cucumbers.
Peronosporosis is activated in cold and rainy weather. The spread of the fungus is facilitated by watering with cold water and temperature changes, and in greenhouses – the formation of condensation on the walls. Light spots on the leaf blades turn brown over time, the process of photosynthesis is disrupted, but the leaves do not fall off. Weak plants die 2 weeks after infection.
Control measures. When the first signs appear, immediately begin treatment of downy mildew. Spray the leaves with solutions of the preparations – Fitosporin-M, Gamair, Consento, Kuprolux, Kurzat, Ordan, Previkur Energy. It is important to carry out the treatment as soon as possible, otherwise the bush will not be saved.
Do not overuse fungicides. In excessive quantities, they harm plants and soil, dry out leaves, slow down shoot growth and reduce plant immunity.
Brown spots on cucumber fruits and leaves
The fruits are covered with brown spots, sometimes with black fungal mycelium. The petioles are ulcerated. The leaves have brown spots with a whitish coating.
Diagnosis: rhizoctonia of cucumber.
The disease causes great harm to crops at the beginning of the growing season. The fungus affects cucumbers both in a greenhouse and in open ground. Moreover, almost all parts of the plant are infected, except for the flowers. The fungus itself lives in the soil, sometimes quite deep (up to 25 cm). Neither humidity nor temperature affect its development. But dense plantings and improper watering allow rhizoctonia to show all its harmfulness.
Control measures. The biological product Trichoderma Veride 471 is effective. For prevention, use the biological product Sporobacterin, and soak the seeds in Baktofit before sowing. Most often, the disease affects fruits that touch the ground, so tie up the vines and mulch the beds.
Dark spots on cucumber leaves
Dark spots appear on the leaves, they merge, after which the entire blade dies.
Diagnosis: black mold (cucumber leaf burn).
Black mold quickly spreads on cucumbers throughout their above-ground parts, including the greens. The disease mainly starts with old leaves, so they should be removed regularly. A special sign: a brown rim remains along the edge of dead tissue.
Control measuresSpray plants with 10% copper oxychloride solution or 0,3% Bordeaux mixture solution every 1 days until symptoms disappear.
Bacterial diseases of cucumbers
Like fungi, bacteria are not asleep and are waiting for their time to infect plants. We will tell you how to treat cucumbers if you find the following suspicious signs.
Cucumber leaves, flowers and fruits are covered with brown spots
A cloudy liquid forms on the lower part of the leaves in the places of these spots, after a while only the veins remain from the leaves. The greens wrinkle and become covered with ulcers.
Diagnosis: bacteriosis, or angular leaf spot of cucumbers.
The disease actively spreads in greenhouses, but can also affect cucumbers in open ground. Hot weather, heavy rainfall and improper watering favor the growth of bacteria. The development of bacteriosis at the beginning of fruiting is especially dangerous, since the cucumbers, even if they grow a little, will be unfit for food.
Control measures. You can’t delay treating bacteriosis. At the first signs, spray the plants with Abiga-Peak or another contact fungicide. Sporobacterin has also proven itself to be effective. Treatment with a 1% solution of Bordeaux mixture or a 0,3% solution of copper oxychloride is also effective. If the root collar is affected, pour a 0,2% solution of Fitolavin under the root (20 ml per 10 l of water).
Dark green water-soaked spots on cucumber leaves and fruits
Watery dark green spots are visible on the leaves, then they turn brown, merge into necrotic formations up to 3 cm in length. The plant loses turgor, the stems soften. The greens become covered with watery spots, from which liquid is released.
Diagnosis: wet bacterial rot of cucumbers.
Plantings can be damaged throughout the entire growing season. Most often, infection occurs through contaminated seeds or rotten plant waste that remains in the beds. It is impossible to eat the fruits: they turn brown inside, and watery mucus is visible. The bush stops growing, the lower leaves dry out. And although there are usually many flowers, there are practically no ovaries, and the fruits grow crooked.
Control measures. To prevent the disease, disinfect the entire greenhouse frame in the fall and pour the soil with a solution of formalin or chloropicrin. At the first signs of damage, spray the cucumber bushes with a 1% solution of Bordeaux mixture. Repeat the procedure after 10-12 days.
Viral diseases of cucumbers
Viral diseases are most often represented by mosaics, which are characterized by unusual leaf colors. They are mainly carried by fleas, aphids and other pests. They also get into the garden through infected seeds.
Mosaic pattern on cucumber leaves
The leaves become covered with colored spots, then curl up. The fruits lose their natural color, become speckled. The flowers dry up, the ovaries fall off.
Diagnosis: common cucumber mosaic virus (cucumber mosaic virus).
The virus can live in the soil for years, and after a temperature change it becomes active. Its first manifestations can be confused with chlorosis. But then the bush noticeably stops growing, the leaves become smaller. Sometimes the stems crack. In a word, mosaic on cucumbers is not at all harmless, and it is better to remove severely affected plants immediately.
The mosaic virus affects not only cucumbers, but also many other garden crops, such as tomatoes, peppers, dill and beans.
Control measures. Every 7-9 days, spray the bushes with a 0,03-0,035% solution of Farmayod, a 10% solution of low-fat milk. Fight aphids that carry the disease, and soak the seeds in a weak solution of potassium permanganate or any other fungicide before sowing.
If there is a lack of nutrition, fungi and bacteria damage, cucumbers may develop chlorosis – a common disease in which the production of chlorophyll is disrupted and the process of photosynthesis slows down. The leaves of the plants turn yellow, and the veins remain green. Then the leaf dies.
To solve the problem, remove weeds, destroy pests and spray the bushes with Antichlorizin, Mik-Reacom or iron sulfate (50 g per 10 l of water). Continue the treatment until the leaves turn green.
Prevention of cucumber diseases
To ensure that plant diseases bypass your garden and you don’t have to think about how to treat cucumbers, follow these simple rules:
- treat seeds before sowing in solutions of Fitolavin or Maxim preparations;
- disinfect all equipment;
- disinfect the soil with a solution of potassium permanganate or chemicals: Fitosporin, Baikal EM1, etc.;
- regulate the temperature and humidity in the greenhouse (the norm is no higher than 28°C and 80%);
- destroy pests and weed;
- observe crop rotation;
- tie the vines to supports so that they have less contact with the soil;
- water cucumbers only with warm, settled water in the furrows, and not at the roots;
- at the end of the season, wash the greenhouse, remove and burn all plant debris, dig the soil deeply;
- Discard diseased and weakened plants, which are most likely to become infected.
Now you know what diseases cucumbers suffer from, what dangers await them in the open air and in greenhouses. When the first signs are detected, do not waste time and immediately save the plants. This way you can minimize crop losses. And preventive measures will help protect cucumber plantings from infection.
