Hawthorn gall midge

The hawthorn gall midge (Resseliella crataegi) is a small insect belonging to the order Diptera and the family Cecidomyiidae. It is an specialized pest that focuses its reproductive and nutritional cycles on plants within the hawthorn genus, causing significant physiological distress to its host.

The primary host plants affected by this midge are species of the genus Crataegus. The larvae induce localized damage to the tender growth of these shrubs, impacting both the aesthetic appearance of the plant and its overall capacity for photosynthesis throughout the active growing season.

The life cycle of the hawthorn gall midge is synchronized with the bud burst and early leaf development of the hawthorn. Adult midges emerge in spring to lay their eggs on the margins of young, unfolding leaves. As the larvae hatch and begin feeding, they secrete substances that cause the leaf tissue to roll and distort, creating a protective gall environment.

The visible impact of the infestation is characterized by tightly rolled leaf margins that hide the larvae inside. As the larvae feed, the distorted leaf sections may become chlorotic and eventually necrotic. Heavy infestations can lead to premature leaf drop and may stress younger or weaker plants, making them more susceptible to subsequent environmental pressures.

Effective management and control of Resseliella crataegi include:

• Manual removal of infested, rolled leaves before the larvae pupate in the soil.
• Pruning and destroying heavily damaged branches during the early summer months.
• Applying systemic insecticides or horticultural oils during the adult egg-laying period if necessary.
• Encouraging a diverse garden environment to support natural predators of gall midges.