Walnut shoot moth

The walnut shoot moth (Acrobasis juglandis) is a destructive insect species belonging to the order Lepidoptera and the family Pyralidae. It is a well-known pest that poses a significant challenge to walnut growers, affecting both orchard productivity and nut quality.

This moth primarily targets the Juglans genus, specifically the English walnut. The larvae are the main destructive stage, as they tunnel into developing buds, young shoots, and nuts. This feeding behavior causes stunted growth and heavy yield losses if left unmanaged.

The life cycle follows a complete metamorphosis. The larvae overwinter in hibernacula (protective silk cocoons) hidden in bark crevices or branch crotches. As spring temperatures rise, the larvae emerge to feed on expanding buds and young foliage, moving to the developing nuts later in the season.

Damage is often visible through the presence of frass (larval waste) trapped in silk webbing on the shoots or nut clusters. Infested nuts often drop prematurely or become susceptible to secondary pathogens, causing fruit rot and significant aesthetic and commercial damage to the harvest.

Integrated Pest Management (IPM) is essential for controlling Acrobasis juglandis. Effective strategies include:

• Sanitation through pruning and destroying infested shoots to reduce overwintering populations.
• Monitoring adult moth flights using pheromone traps to determine the timing of insecticide applications.
• Applying systemic or contact insecticides during the larval emergence period.
• Encouraging natural predators and parasitoids within the orchard environment to maintain ecological balance.