Sweet potato webworm

The sweet potato webworm (Brachmia convolvuli) is a moth species belonging to the order Lepidoptera and the family Gelechiidae. This insect is primarily recognized as a significant agricultural pest, specifically adapted to feed on plants within the Convolvulaceae family, causing notable damage to commercial crop production.

The primary host for this pest is the sweet potato (Ipomoea batatas). While it also utilizes wild Convolvulus species as alternative hosts, the commercial cultivation of sweet potatoes provides an ideal environment for the moth to thrive, often leading to localized outbreaks during the peak growing season.

The biological cycle of Brachmia convolvuli includes egg, larval, pupal, and adult stages. Females lay eggs on the undersides of leaves. Upon hatching, the larvae immediately begin feeding and constructing protective webbing, which is characteristic of their behavior. The entire development process is highly dependent on temperature, with warmer conditions accelerating the reproductive rate.

The damage caused by these larvae is distinct and easily identifiable. They skeletonize the leaves and tie them together with silk threads to create shelters. This activity severely inhibits the plant's ability to perform photosynthesis, resulting in stunted growth, reduced tuber size, and, in severe cases, the total defoliation of the crop canopy.

Effective management requires a combination of Integrated Pest Management (IPM) techniques. Key control measures include:

• rigorous weed management to eliminate alternative hosts like bindweed;
• sanitation of fields by removing crop residues after harvest to disrupt the pupation cycle;
• application of target-specific insecticides during the early larval stage.