Diseases of cucumberscan occur on both ground and greenhouse cucumbers. Among them we find fungal, bacterial and viral diseases. The most common symptoms are yellowing, browning, spots, rot and deformation of the leaves and fruits of the cucumber. In this article, you will learnhow to recognize cucumber diseases , what are the characteristic symptoms of these diseases and how to combat pathogens that attack vegetables. We also recommend the bestspraying for cucumber diseases !
Why do cucumbers get sick and how to treat them?
Fig. depositphotos.com
Fungal diseases of cucumbers
Themost common fungal diseases of cucumbersinclude: powdery mildew of cucurbits and downy mildew of cucurbits. Both types of powdery mildew can attack both field and greenhouse cucumbers, although, for example, in the case of field cucumbers, powdery mildew does not cause large losses (the disease appears in the final stage of cultivation and mainly affects the leaves). Field cucumbers are often susceptible to cucumber anthracnose, and greenhouse cucumbers to black rot and cottage cheese rot.
sowing and mulching the soil so that the leaves and ripening cucumber fruits do not come into direct contact with the ground. It is also helpful to grow cucumbers on strings or other supports, thanks to which the cucumbers do not fall on the ground and it is easier to water the plants without soaking the leaves. By the way, it will be easier to care for plants and harvest cucumber fruits. After finishing the cultivation, clean the beds of the remaining remnants and
do not grow cucumbers in the same placefor another 3-4 years.
Cucurbit anthracnose
Cucumber anthracnosisis a disease that affects cucumbers and is rarely found under cover. It is caused by the pathogen Colletotrichum orbiculare. As a result of the infestation, small yellowish spots appear between the veins on the surface of the leaf blade, which eventually coalesce, and the entire leaves turn yellow and fall off. The infection spreads to the shoots and it infects the cucumber fruit.Affected cucumbers become covered with rotting spots, on the surface of which you can see a pink coating of myceliumAnthracnose can attack fruit tissues up to a depth of 3-4 mm. The fungus spores spread with infected plant debris or seeds collected from diseased plants.
Prophylaxis is based primarily on removing plant debris from flower beds after the end of cultivation, rotating vegetables (cucumbers should not be planted in the same position for 2-3 years), deep autumn plowing and seed dressing before sowing.If you notice the first symptoms of the disease on plants, remove the infected plant parts on an ongoing basis, and spray the fungicide Switch 62.5 WG or Scorpion 325 SC.
Korynes porosis of cucurbits
Korynespora cassiicola is a disease caused by the pathogen Corynespora cassiicola thatinfects the fruit buds of cucumbers grown under coverOn older leaves, it causes angular olive-colored spots with a yellow border that blend together and cover with a black coating of mycelium. On the stems and petioles, the spots take on a more oblong shape. This thermophilic fungus feels great at 28-30 ° C and poses the greatest threat in the summer.Cucumbers are most at risk of infectiongrown in blast furnaces heated tunnels.
The fungus spores overwinter in plant debris, which, along with infected seeds, are a frequent source of infection.Toprevent this disease in cucumbers , clean tunnels and greenhouses, ventilate frequently, clean up plant debris and treat seeds before sowing. Prophylactically, we can use copper fungicides, such as Miedzian 50 WP and Miedzian Extra 350 SC, spraying at 14-day intervals, ending 3-4 weeks before harvesting.
Powdery mildew of cucurbits
Powdery mildew of cucurbitsis a fungal disease that appears on the leavesspots covered with white mycelium coatingOver time, the spots merge and become a bit darker. As the disease progresses, the petioles and stems are also affected. The leaves deform, the surface folds, and eventually the leaves fall. The fruits are not damaged but due to weakening the whole plants wilt and die.
Cucurbit mildew may be caused by the pathogens Erysiphe cichoracearum and Sphaerotheca fuliginea.In both cases, the symptoms of the disease are identical. The spores of the fungus often hibernate in plant debris, e.g. in greenhouses, from where, when carried by the wind, they can infect plants in the ground.Optimal conditions for the development of powdery mildew are high air humidity and insufficient amount of lightThe use of cold water for watering plants, especially in hot and dry weather, also contributes to infection. The rapid growth caused by the use of too high doses of nitrogen fertilization also exposes the plants to infection.
Powdery mildew of cucumber leaves
Fig. depositphotos.com
To prevent the emergence or spread of this disease of cucumbers, it is best tocultivate varieties resistant to mildew , strengthen the plants with appropriate fertilization, and after harvesting carefully remove the remnants from the field and greenhouse vegetable.
Powdery mildew on cucumbers can be combatedusing natural preparations based on horsetail, nettle or grapefruit.If we do not have time to prepare decoctions and extracts of weeds and herbs on our own, you can reach for ready-made preparations, such as Evasiol (based on horsetail), Nettle growth stimulant (equivalent to nettle slurry) and Biosept Active (grapefruit seed extract, which immunizes plants for diseases and supports their regeneration). In the event of a rapid development of the disease, chemical agents such as Siarkol Extra 80 WP and Scorpion 325 SC can be used.
Downy mildew of cucurbits
Downy mildew of cucurbitsis caused by Pseudoperonospora cubensis. This most dangerous of cucumber diseases causes significant losses in crops. Under certain conditions, all plants can die within a few days.
The first symptoms of infection can be seen on the leaves -olive, watery discoloration between the veinsOn the underside of the leaf blade, within the infected tissue, clusters of brown spores of the fungus appear.Infected leaves turn yellow, then turn brown and die. Humid and cool nights (approx. 13 ° C) as well as warm and sunny days promote the development of the disease. Long-lasting night fog also contributes to the spread of the fungus spores.
Downy mildew of cucurbits
Fig. depositphotos.com
Downy mildew of cucurbits is a disease of cucumbers that is quite difficult to combat. The spores of the fungus are carried long distances by the wind. That is why prevention is so important - location of the cultivation away from water and other plantings, mulching the soil, fertilization with phosphorus during the setting of cucumber fruits.
We can fight downy mildew on cucumbersby spraying with natural preparations - extracts of nettle, horsetail, yarrow, garlic, onion or nettle liquid manure. It is worth planting basil and garlic in the vicinity of cucumbers - the presence of these species reduces the risk of infection.
If, despite the ecological spraying , symptoms of downy mildew of cucurbitsappear on cucumbers, spraying with copper or sulfur preparations is performed. For amateur crops on plots and in gardens, Miedzian 50 WP and Siarkol 800 SC will be a good choice.
Pumpkin scab
Cucurbit scab is a disease caused by the fungus Cladosporium cucumerinum.Symptoms of this disease of cucumberscan be seen on all the above-ground organs of the plant. Brown spots with a yellow border appear on the leaves, which look like water-soaked spots. Over time, in these places, the tissue dries up and crumbles, and as a result, holes are formed in the leaves. Stains also appear on the stems.On cucumber fruits you can see watery spotswhich become concave over time. Such fruits are unfit for consumption.
Cuckoo scab attacks both ground and greenhouse cucumbers Humid, warm and windy weather favors the development of the disease. To prevent scab infection, sow cucumber-resistant varieties, regularly weed cucumber beds, remove plant debris from the beds after cultivation, and follow the rules of crop rotation. Among the chemical pesticides, the only one registered for use in amateur cropsagainst cucumber scabis Scorpion 325 SC.
Pumpkin scab
Fig. Rasbak, CC BY-SA 3.0, Wikimedia Commons
Black root rot of cucurbits
Black root rot caused by the fungus Phomopsis sclerotioides is a very serious diseasedisease of cucumbers grown under cover on straw and in the groundCauses root rot in the soil. As a result, the plant has limited access to water and nutrients and dies.The spores of the fungus hibernate in the soil and are extremely viable. They spread with water, infected plant debris and seeds.
An effective method of combating this disease of cucumbersis soil disinfection with steam. The preparation Magnicur Energy 840 SL can be used for disinfecting the substrate and watering plants.
Curd rot
Curd rot caused by the pathogen Sclerotinia sclerotiorum is a serious problem in the cultivation of many vegetable species, especially under cover.Symptoms of this disease of cucumberscan be seen on all organs of the plant in the form of a thick, woolly, white coating with black spore spots. It also happens that symptoms appear only during the storage of cucumber fruits.
The most effectivemethod of fighting this disease of cucumbersis prophylaxis, because spore forms in the soil remain viable for up to 12 years.First of all, the infected plants should be removed immediately and greenhouses or tunnels should be ventilated frequently, as the development of the disease is favored by high soil and air humidity.
As a preventive measure, the soil can be sprayed with Contans, which includes the fungus Coniothyrium minitans, which is a parasite of sclerotia and mycelium causing sclerosis rot. Unfortunately, the preparation is currently available only for professional users (e.g. for agricultural crops). In amateur crops, after diagnosing the disease, chemical agents such as Switch 62.5 WG or Scorpion 325 SC can be used.
Cucumber gumoza
Black rot of buds and shoots, also known as cucurbits, is a fungal disease caused by the pathogen Didymella bryoniae and affects the above-ground parts of plants. It manifests itself byspots on leaves and shoots as well as rotting of the tips of the cucumber fruitThe infection is fostered by too high air humidity.Black rot penetrates the plant through flowers and mechanical injuries.
Pumpkin gumosis on watermelon shoots
Fig. David B. Langston, CC BY-SA 3.0, Wikimedia Commons
We should take care of cleanliness as a prophylactic: disinfect tools, clean plant residues and maintain air humidity under covers below 80%, and avoid large temperature fluctuations.
Plants are positively influenced bybiological spraying with Prestop WP , which, thanks to the spores of the parasitic fungus Gliocladium catenulatum, prevents the development of black rot on cucumber. Unfortunately, at the time of writing this article, we were unable to find small packages of this agent intended for amateur cultivation. Although theoretically the preparation is allowed to be used in amateur crops, the smallest packaging available in stores is 1 liter. In practice, therefore, the use of this agent on a small scale of crops, e.g.in home gardens may be unprofitable.
Bacterial diseases of cucumbers
Bacterial angular cucumber spot , caused by the bacterium Pseudomonas syringae pv. lachrymans, manifests itself in tiny olive water-soaked spots on leaves, shoots and fruits. Mucous discharge appears in places of discoloration. Infected tissue dries quickly and crumbles, leaving holes surrounded by a white border. This last symptom is quite easy to confuse with cucurbits scab, as a result of which quite similar holes appear in the leaves.
Bacterial angular blotch of cucumber
Fig. Clemson University - USDA Cooperative Extension Slide Series, CC BY-SA 3.0, Wikimedia Commons
With high air humidity, the disease develops very quickly and mainly affects cucumbers grown in a greenhouse. It is spread by wind, water droplets and infected seeds.It can also be spread by pests of cucumbers. It can overwinter in plant residues and seeds, so you should take 2-3 years of breaks in the cultivation of cucumbers in the same place, and take care of the hygiene of the crops. It is worthto use mustardas a forecrop for cucumbers, which limits the development of infection.
To combat this disease of cucumbersyou can use Miedzian Extra 350 SC as a preventive measure.
Viral diseases of cucumbers
Cucumber mosaic is a viral diseasetransmitted mainly by aphids. The first symptoms of the disease appear as mosaic-like chlorosis on young plants. As the disease progresses, the leaves wrinkle, shrink, and their edges curl downwards. On cucumber fruits, the virus stimulates the formation of lumpy lumps.
Cucumbers infected with the virus should be removedas they cannot be cured. Keeping crops hygienic, combating aphids and disinfecting are actually the only ways to prevent this disease.
MSc Eng. Anna Błaszczak
