Walnut husk fly

Taxonomic position: The walnut husk fly (Rhagoletis completa) belongs to the order Diptera, family Tephritidae. It is a significant agricultural pest that specifically targets the husks of walnut fruits, causing extensive economic losses by rendering the nuts unmarketable.

Host plants: The primary host is the English walnut (Juglans regia). The pest also affects black walnuts (Juglans nigra) and other related Juglans species. Native to North America, it has spread to various regions worldwide, becoming a major quarantine concern for walnut production areas.

Biology and life cycle: The adult flies emerge from the soil during mid-summer. After mating, females puncture the green husk of the fruit to deposit eggs in clusters. The larvae hatch and tunnel through the husk, feeding on its tissue for several weeks. Once mature, larvae exit the fruit, drop to the ground, and pupate in the soil, where they overwinter until the next year.

Nature of damage: Feeding larvae destroy the green outer layer of the walnut, known as the husk. This causes the husk to turn mushy and black, leading to staining of the shell and internal kernel decay. Severe infestations result in early fruit drop, significant reduction in yield, and loss of quality, as the nuts become shriveled and prone to fungal growth.

Control measures: Integrated Pest Management (IPM) is essential for controlling this species.

• Deploying yellow sticky traps to monitor adult flight and reduce local populations.
• Sanitation practices, including the daily removal and destruction of fallen infested nuts to break the cycle.
• Cultivation of the soil under the tree canopy to expose or crush pupae.
• Timely application of registered insecticides based on trap monitoring results during the adult activity season.