Cotton stem weevil

Pempherulus affinis, commonly known as the cotton stem weevil, belongs to the family Curculionidae within the order Coleoptera. This insect is recognized as a major pest of cotton, causing significant economic losses in various tropical regions by attacking the main stem of the host plant.

The primary host for this pest is the cotton plant (Gossypium). The larvae are internal feeders, living inside the stem, which makes them difficult to control once they have bored into the plant tissue, as they are shielded from many conventional contact insecticides.

The life cycle of the pest involves the female laying eggs in the bark of the cotton stem. After hatching, the larvae tunnel through the tissue, feeding and creating chambers where they eventually pupate. The duration of each developmental stage is heavily influenced by ambient temperature, allowing for multiple generations per year under favorable conditions.

Symptoms of infestation include the formation of distinct swellings or galls on the stem at the points of larval entry and feeding. These galls weaken the structural integrity of the plant, disrupting the xylem and phloem transport, which leads to stunted growth, wilting, poor boll development, and increased susceptibility to lodging.

Management strategies for this pest include:

• Implementation of strict post-harvest crop residue destruction.
• Crop rotation to break the pest's reproductive cycle.
• Application of systemic insecticides directed at the base of the plant during the early growth stage.
• Maintaining field sanitation to prevent the build-up of overwintering populations.