The planting dates for soybean in Louisiana range from early March to late June, depending on production systems and maturity groups. This variability in planting dates can expose soybean plants to a myriad of insect pests that can injure both below and above ground plant parts.
Soybean seedlings can generally tolerate substantial injury from insect pests. However, some situations may affect the ability of soybean plants to compensate for injury.
The primary early-season insect pests of soybean are bean leaf beetle, three-cornered alfalfa hopper, wireworms, grape colaspis, and thrips.
General conditions where the use of insecticidal seed treatment may be warranted:
- early-planted soybean where fluctuations in environmental conditions add stress to seedlings, making the plants more vulnerable to insect injury
- late-planted soybean where seedlings may be exposed to high insect pest pressures
- soybean planted into wheat stubble, a favorable environment for three-cornered alfalfa hopper development
- weedy fields
- conservation tillage production system
- areas with historically high numbers of problematic insect pests
- planting directly into cover crops
Compared to previously stated situations, risks associated with insect damage are reduced when soybeans are planted at the recommended planting window, under optimal soil conditions, and historically low insect pest densities. Thus, insecticidal seed treatments are much more important when planting occurs in suboptimal conditions compared to timely and optimal conditions. In addition, these products are generally effective in soybean for only 30 days.
Refer to the “2022 Louisiana Insect Pest Management Guide” available at the LSU AgCenter website for more ways to manage insect pests of soybean.