Secondary screwworm

The secondary screwworm (Cochliomyia macellaria) is a member of the order Diptera and the family Calliphoridae. While primarily recognized as a medical and veterinary pest, it poses significant indirect risks to agricultural operations by acting as a vector for pathogens and causing trauma to livestock.

The pest does not feed on plant tissues but thrives in agricultural environments where animal waste, decaying organic matter, and carrion are present. Its presence in farm settings often indicates poor sanitary management, which can indirectly affect the health of surrounding crops by increasing the concentration of fly-borne bacteria.

The biological cycle of the insect consists of four stages: egg, larva, pupa, and adult. Females lay clusters of eggs on necrotic organic substrates. The larvae develop rapidly, often within a few days, depending on environmental temperatures. This rapid turnover allows populations to explode during warm, humid seasons.

The damage caused is primarily attributed to myiasis, where larvae infest open wounds or sores on animals. While they prefer dead tissue, they can invade living flesh, causing extensive tissue destruction, severe irritation, and potential secondary bacterial infections that significantly reduce the productivity of farm livestock.

Effective control measures focus on environmental sanitation and habitat disruption. Key strategies include:

• Prompt disposal of carcasses and biological waste;
• Implementation of rigorous manure management programs;
• Application of approved insecticides in breeding areas;
• Installation of physical barriers like screens in livestock shelters to prevent adult fly access.