Elm gall midges

The primary host plants affected by these midges are members of the genus Ulmus, including the smooth-leaved elm and the wych elm. Younger trees and nursery saplings are particularly susceptible, as their rapid spring growth coincides with the peak activity period of the adult midges.

The life cycle of the elm gall midge is deeply integrated with the seasonal growth of the host plant. Adult females lay their eggs within the developing tissue of leaves or young stems. Upon hatching, the larvae secrete substances that stimulate the host plant to produce a gall, which serves as a protective chamber for the larva to feed and complete its development.

The damage caused by these insects is characterized by leaf curling, swelling, or the formation of distinct horn-like galls on the foliage. Heavy infestations can lead to premature leaf drop, stunted shoot growth, and a general decline in the tree's vigor, making it more susceptible to environmental stress and opportunistic secondary pathogens.

Effective control strategies require a combination of preventative and corrective measures:

• Sanitation by removing and destroying fallen leaf litter during the autumn to reduce the overwintering population.
• Applying systemic insecticides in the early spring, specifically timed with the oviposition phase.
• Maintaining healthy tree conditions through proper watering and fertilization to enhance natural resistance.
• Encouraging natural predators, such as parasitic wasps and ladybugs, to help manage the population density.