Damage Pattern
Damage is caused by both adult beetles and larvae. The larvae feed heavily on the roots, reducing the supply of water and nutrients, leading to increased risk of lodging and the typical “goose neck” symptom. Adult beetles feed on stigma threads and pollen, disrupting fertilization and grain development. They also cause stripe feeding on the leaves.
Biology and Temporal Occurrence
The adult beetle is 5-7 mm long with a dark head and yellow to rusty-brown color. It appears from early July, primarily in August. Oviposition occurs in early fall, with 500-1,000 eggs per beetle laid in the upper 15 cm of soil. Larvae hatch the following summer, feeding on the roots, causing damage, and making infested plants easy to pull from the soil. After 4-5 weeks, they pupate and emerge as beetles. Beetles can fly up to 30-40 km per year.
Control
Chemical control is generally not recommended due to resistance. SoilGuard 0.5 GR, a granulated insecticide, can be applied at sowing to control the larvae, but it does not affect the beetles. Preventive measures include expanding crop rotations that reduce maize acreage and planting crops not favored by the rootworm (e.g., pumpkin, millet, soy). Selecting varieties with strong, regenerative roots can also help.