Identification of 8 Common Cucumber Pests and Diseases and Pesticide Control Methods

Cucumbers are widely cultivated across China and are one of the main greenhouse products. In production, pests and diseases often occur together, so when controlling them, pesticides should be reasonably combined, and the dosage should be flexibly adjusted according to the stage of disease development.

Disease control: identify the symptoms, apply the right pesticide

Downy mildew is most damaging in low-lying areas with poor ventilation and excessive watering. It mainly attacks the leaves, first appearing as water-soaked, angular lesions; under high humidity, black mold grows on the underside of the leaves, and once the lesions merge, the leaves wither prematurely. For control, keep daytime temperatures at 25°C and nighttime temperatures at about 15°C while maintaining ventilation; when the disease appears, spray with 50% Juncheng diluted 2000 times with water, and repeat once every 3~5 days in severely affected fields.

Powdery mildew mainly attacks leaves and vines, first appearing as white, nearly circular powdery patches that later join into large white powdery areas, with the diseased leaves turning yellow and withered in the later stage. Choose disease-resistant varieties, ensure good light penetration, water reasonably, reduce humidity, and apply plenty of organic fertilizer; in the early stage of the disease, spray with Tiannuo Keli Feng fungicidal type diluted 1000 times, spraying 2~3 times in a row at 5~7 day intervals.

Gray mold: the pathogen enters through withered female flowers, produces a gray-brown mold layer, then invades young fruits, causing the tops to rot and shrivel, while larger fruits turn yellow and drop off. It is best to use high-ridge cultivation, reduce humidity, water in the evening and ventilate to remove moisture; in the early stage of the disease, spray with 50% Sumilex diluted 1500~2000 times or 50% Duomeiling diluted 800~1000 times.

Anthracnose attacks stems, leaves and fruits. Leaf spots are reddish-brown and nearly circular with a halo around them, while fruit spots are dark brown and easily deformed. Rotate with @non-cucurbit crops for more than 3 years, disinfect the soil, clear away crop residues, and apply more phosphorus and potassium fertilizer; spray with 1:2:100 Bordeaux mixture or 65% mancozeb diluted 500~800 times, or fumigate with 250 grams of 45% chlorothalonil smoke agent per mu, once every 7~10 days for 3~4 consecutive applications.

Bacterial angular leaf spot: the lesions are angular, limited by the leaf veins, and under high humidity white bacterial ooze appears on the underside of the leaves, with perforation in the later stage. Before sowing, soak the seeds in 55°C warm water for 15 minutes to disinfect them; in the early stage of the disease, spray with 70% Keshade diluted 400 times or Xinzhi Meisu diluted 500 times, once every 7~10 days for 3~4 consecutive sprays.

Pest control: management first, biological and physical methods preferred

Leafminer larvae tunnel through the leaf mesophyll, forming winding feeding trails; damage is severe from the 2~7 leaf stage at the seedling stage, and the leaves turn yellow, wither and fall off. Parasitic wasps such as Diglyphus isaea, Dacnusa sibirica and Opius spp. can be released; at peak periods, use 5% fipronil at 50~100 ml per mu or 40% Qixingbao diluted 600~800 times, once every 5~7 days for 2~3 consecutive treatments; when using 50% phoxim diluted 1000 times, stop application 7 days before harvest.

Whiteflies gather to cause damage, secreting honeydew that contaminates leaves and fruits and triggers sooty mold. Cultivate insect-free seedlings, add nylon mesh to ventilation openings, do not intercrop with tomatoes or common beans, and remove and burn old leaves; when adult whiteflies are below 0.5 per plant, release Encarsia formosa, once every two weeks for a total of 3 releases, at 15 insects per plant; hang orange-yellow sticky traps at 32~34 per mu, and recoat the sticky oil every 7~10 days; for chemical control, use 2.5% deltamethrin or 20% fenvalerate diluted 2000 times, spraying 3 times in a row at 6~7 day intervals.

After melon aphid damage, leaves curl, seedlings wilt or even die, old leaves drop early, and the fruiting period shortens, reducing yield. Yellow sticky boards can be used to trap aphids, and natural enemies such as the seven-spotted ladybird, Chrysopa sinica and aphid parasitoid wasps should be protected; when damage is found, spray 100 ml of 0.65% shanghaosu mixed with 30~40 kg of water, or 2.5% derris extract diluted 600~800 times, or 10% imidacloprid diluted 2000 times, then spray again after 10~15 days.

In short, install qualified insect-proof nets, detect and control pests and diseases promptly, and eliminate them while they are still in the spot-and-patch stage; give priority to physical and biological control, and only use chemical control when outbreaks occur, paying attention to rotating and combining pesticides.