Symptom Identification and Control Methods for Aphids and Root-Knot Nematodes in Cucumbers

Cucumber is a widely grown annual climbing or trailing herbaceous plant of the Cucurbitaceae family, and during its growth it is highly prone to two pests: aphids and root-knot nematodes. Below is an introduction to the symptoms and control methods for these two pests.

Symptoms and Control Methods for Aphids

Main symptoms: aphids, also known as plant lice, are pests that commonly occur in cucumber production. They cluster on the undersides of melon and vegetable leaves or on young tender stems and buds, sucking sap, causing leaves to curl and become deformed, and spreading viruses. When aphids cause damage, they also excrete large amounts of honeydew that contaminates leaves and fruits, leading to parasitic sooty mold infection and affecting photosynthesis.

Control methods:

(1) Clean up the field. Promptly remove weeds in the field and along field edges, dispose of dead branches and fallen leaves, and promptly spray disinfectant agents for disinfection.

(2) Physical and biological control: use yellow sticky boards to trap and kill them, cover the ground with silver-gray film or hang strips of silver-gray film in greenhouses, conservatories and other fields, which can repel insects. For biological control, microbial pesticide BT emulsion can be sprayed for control.

(3) Strengthen field management, improve plant disease resistance, and apply additional fertilizer and water reasonably.

(4) Prepare tobacco leaf water at a ratio of 1:15, soak for 4 hours, then spray.

(5) Prepare a solution of washing powder, urea and water at a ratio of 1:4:400 and spray.

(6) Use 95% mineral oil at 200 times dilution, applied 3-4 times consecutively; or control with nicotine, veratrine, etc.

(7) Use natural enemies such as ladybugs and green lacewings for control.

Symptoms and Control Methods for Root-Knot Nematodes

Main symptoms: cucumber root-knot nematode disease mainly affects the lateral roots and fibrous roots of cucumbers. When fibrous roots or lateral roots are infected, root knots of varying sizes form, ranging from light yellow to yellow-brown. When root knots are dissected, many slender, wriggling milky-white nematodes can be seen parasitizing within the diseased tissue. Above the root knots, thin and weak new roots generally grow out, forming root-knot tumors after infection. Mildly diseased plants show no obvious symptoms on the aboveground parts; when the disease is severe, plants are noticeably stunted, bear few and small cucumbers, leaves fade to yellow, and on sunny days at noon the aboveground parts of the plants wilt or gradually turn yellow and withered, eventually resulting in plant death.

Control methods:

(1) Select disease-resistant and disease-tolerant varieties.

(2) Use disease-free soil for seedling cultivation, and cultivate disease-free strong seedlings.

(3) Promptly remove diseased plants found during transplanting.

(4) Implement a crop rotation of more than two years with vegetables such as onions, garlic and Chinese chives. For severely affected plots, it is best to rotate with gramineous crops; rotation between paddy and dryland crops gives the best results.

(5) Deep plowing or soil replacement. When changing crops in summer, plow more than 25 cm deep while adding fully decomposed organic fertilizer; or replace all the topsoil within 25 cm.

(6) After cucumber vines are pulled up, promptly remove diseased and residual roots, bury them deeply or burn them, and eradicate field weeds.

(7) Soil disinfection treatment under high summer temperatures. In high summer temperatures, spread wheat straw 5 cm thick in the greenhouse, then spread about 100 kg of superphosphate, turn it into the soil, cover with plastic film, and seal the greenhouse, so that the greenhouse temperature reaches above 70°C and the soil temperature at a depth of 10 cm reaches about 60°C, keeping the greenhouse sealed for 15-20 days.

(8) After cucumber vines are pulled up and before planting the next crop, plant a short-growth-period and highly susceptible crop, such as baby bok choy or spinach; after they become infected, dig them all out of the greenhouse and apply pesticide treatment to the loosened soil surface.