Symptom Identification and Control Methods for Cucumber Aphids and Root-Knot Nematodes

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

Symptoms and Control Methods of Aphids

Main symptoms: Aphids, also known as greenflies, are pests that frequently occur in cucumber production. They gather on the undersides of leaves or on young tender stems and buds, sucking sap and causing leaves to curl and become deformed, and they also transmit viruses. When aphids cause damage, they also excrete large amounts of honeydew that contaminates leaves and fruits, causing sooty mold fungi to parasitize, which affects photosynthesis.

Control methods:

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

(2) Physical and biological control: Use yellow sticky boards to trap and kill them, use silver-gray plastic film for ground mulching, or hang strips of silver-gray plastic film in fields such as greenhouses and glasshouses, 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, let it steep for 4 hours, then spray.

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

(6) Use 95% mineral oil at a 200-fold dilution, applied 3-4 times consecutively; or use nicotine, veratrine, and the like for control.

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

Symptoms and Control Methods of Root Nematodes

Main symptoms: Cucumber root-knot nematode disease mainly damages the lateral roots and fibrous roots of cucumber. When fibrous roots or lateral roots are infected, root knots of varying sizes form, ranging from light yellow to yellowish-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. On mildly diseased plants, the aboveground symptoms are not obvious; when the disease is severe, the plants are noticeably stunted, bear few and small cucumbers, and the leaves turn chlorotic and yellow. At noon on sunny days, the aboveground parts of the plants wilt or gradually wither and yellow, and eventually the plants die.

Control methods:

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

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

(3) Remove diseased plants promptly when found during transplanting.

(4) Carry out crop rotation with vegetables such as scallions, garlic, and chives for more than two years. For severely affected plots, it is best to rotate with grass-family crops; paddy-upland rotation gives the best effect.

(5) Deep plowing or soil replacement. When changing crops in summer, plow deeply and turn the soil more than 25 cm, while applying 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 the high heat of summer, 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 tightly, so that the greenhouse temperature rises above 70°C, the temperature in the soil at a depth of 10 cm reaches about 60°C, and keep the greenhouse closed for 15-20 days.

(8) After cucumber vines are pulled up and before planting the next crop, plant short-growing-season and easily susceptible crops, such as baby bok choy and spinach, and after they are infected, dig them all out of the greenhouse, then carry out pesticide treatment on the loosened soil surface.