Pasture webworm

Loxostege affinitalis, commonly known as the pasture webworm, is a moth species in the family Crambidae. It is a recognized agricultural pest, particularly in Australia, known for its significant impact on broad-acre crops and pasture production during favorable environmental conditions.

The pest poses a threat to a variety of crops, primarily targeting soybeans, sunflowers, cotton, and various legume pastures. It is opportunistic, frequently moving from native grasses and weeds onto emerging or established crops, which complicates early detection and management efforts.

The life cycle consists of the egg, larval, pupal, and adult stages. The female moth lays eggs on host plants, and larvae typically emerge within a few days. The larvae are the primary damaging stage, moving across the soil or plant surface and sometimes creating webbed shelters for protection.

Feeding damage involves larvae consuming foliage, which can range from minor leaf-shredding to total defoliation of the crop. In severe cases, the caterpillars strip the plants entirely, leading to significant yield losses or the complete necessity of replanting affected field areas.

Integrated pest management (IPM) is essential for effective control. Growers should focus on crop scouting, maintaining weed-free field margins, and utilizing biological controls where possible. Chemical intervention with registered insecticides should be targeted at the larval stages before significant damage occurs.