How to control soybean leaf rollers in soybean cultivation
The soybean leaf roller is a major pest in soybean production in summer and autumn. Besides damaging soybeans, it also harms leguminous plants such as mung beans and peanuts. In recent years, as winter temperatures have risen, its overwintering population has increased, and its occurrence in soybean fields has worsened year by year. Currently it is the damage period of the soybean leaf roller, and control should be carried out promptly.
The soybean leaf roller damages soybean leaves as larvae. Before the 3rd instar, they prefer to feed on the leaf mesophyll without rolling the leaves; after the 3rd instar, they begin to roll the leaves. The 4th-instar larvae roll soybean leaves transversely into tubes and hide inside to cause damage. Sometimes several leaves are rolled together, often causing flower and pod drop. Adults hide by day and emerge at night, are phototactic, and prefer to be active in the evening. Eggs are laid singly on the underside of soybean leaves. After the larvae mature, they pupate in the rolled leaves.
According to relevant information, the soybean leaf roller enters the peak occurrence period of the first-generation larvae from mid-July to early August, with the most severe damage from late July to early August. The rate of rolled-leaf plants in the field increases substantially, and in severely affected fields the rate of rolled-leaf plants reaches more than 90%. From mid-to-late August it enters the peak pupation period. From late August to early September is the occurrence period of the first-generation adults, and September is the peak damage period of the second-generation larvae. Rainy and humid climates are favorable for the occurrence of the soybean leaf roller; densely growing soybean fields, late-maturing varieties, varieties with few leaf hairs, fields with excessive nitrogen fertilizer application, or late-sown fields suffer more severe damage.
Chemical control is currently an important means of preventing and controlling the soybean leaf roller. Control should begin at the early peak stage of egg hatching for each generation (when 1%-2% of plants in the field are found to have rolled-leaf damage), once every 7-10 days, for 2 consecutive applications. Optional pesticides include cyhalothrin, beta-cypermethrin, fenvalerate, chlorpyrifos, indoxacarb, fipronil, tebufenozide, abamectin, and others.