Plum flower gall midge

The plum flower gall midge (Contarinia pruniflorum) is a specialized insect pest belonging to the Cecidomyiidae family within the order Diptera. This minute fly is a significant threat to stone fruit production, primarily targeting the reproductive stages of host trees, leading to substantial yield losses.

This pest is primarily found on plums, mirabelle plums, and sloe. By infesting the floral buds, the larvae prevent proper pollination and fruit set, which can result in severe economic damage for orchardists if the infestation density is high during the early spring blossoming period.

The biological cycle is synchronized with the phenology of the host plant. The midge overwinters as larvae within cocoons buried in the topsoil. As spring arrives, pupation occurs, followed by adult emergence during the bud swell stage. Females lay their eggs directly into the developing flower buds, where larvae then hatch and begin feeding.

The characteristic damage is the malformation of flower buds, which become swollen, spherical, and exhibit an abnormal yellowish color. These infested buds fail to open and eventually drop prematurely, significantly reducing the fruit load of the tree. The lack of fertilization is the direct result of the larval feeding on the floral interior.

Integrated pest management strategies are essential for control. Cultivation practices, such as tilling the soil around the tree base, help disrupt the pupation process. Furthermore, well-timed chemical interventions with approved insecticides during the 'pink bud' stage are critical to target the adults before egg-laying occurs.

• Deep soil cultivation in autumn to expose larvae to winter conditions.
• Use of soil barriers to prevent adult emergence in spring.
• Application of systemic or contact insecticides before flowering.
• Regular monitoring of bud development for early detection.