Soybean Stalk Weevil
· Bean · Soybean
Larvae and adults of Sternechus subsignatus feed on tender stem tissues, mostly during early vegetative stages. Females clip petioles of the leaves and and girdle stems to lay their eggs nearby the damaged tissue, covering them with cut fibres and tissue pieces. Soon after the larvae hatch, they penetrate the stem and feed on the internal tissue, mostly from a stationary position. As they grow and damage the inside of the stem a gall is formed in the girdled part of the stem.
Sternechus subsignatus is active from the early stages of plant development to harvest. The insect spends the latency phase (when soybean plants are not available) in the soil. Before the harvest period, the larvae jump onto the ground and enter hibernation, protected in chambers formed with soil particles. Adults emerge from the soil gradually over a long period of time. Due to the length of the respective life stages, adult, larvae and eggs phases usually overlap on the same plant or field.
No biological control of the pest has been described so far.
Always consider an integrated approach with preventive measures together with biological treatments if available. Chemical control of populations is possible during the periods the larvae spend inside the stalks (about 30 days) and in the soil. Seed and foliar insecticides can also protect the crop, but they only provide short-lived protection, since continuous adult emergence leads to rapid crop reinfestation.