Cone fly

The cone fly (genus Strobilomyia) belongs to the family Anthomyiidae, order Diptera. These insects are significant pests of coniferous trees, as their larvae specialize in feeding on the developing seeds within the cones of various conifer species, including spruce, larch, and pine.

The life cycle of the cone fly is strictly timed with the growth and development of host tree cones. Adult flies emerge in early spring, synchronized with the cone-bud flush of their host trees. Females deposit their eggs under the scales of young, tender cones, ensuring the larvae have immediate access to their food source upon hatching.

Once hatched, the larvae bore into the cone axis and feed extensively on the developing seeds. This feeding activity causes substantial destruction of the seed crop. By the time the cones reach maturity, the larvae are fully grown, exit the cones, and drop to the forest floor to pupate in the soil or leaf litter, where they overwinter.

Infestation symptoms include premature yellowing or necrosis of cones and the presence of frass or exit holes on the exterior of the cone scales. The damage is economically severe, particularly in seed orchards and nurseries, where the yield of high-quality, viable seeds is significantly reduced due to larval feeding.

Integrated pest management strategies are essential for controlling Strobilomyia populations.

• Monitoring adult emergence using pheromone or visual traps during flowering.
• Removing and destroying infested cones before larvae exit.
• Applying targeted insecticides in seed orchards during the peak adult activity period.
• Promoting biodiversity in forests to encourage natural predators and parasitoids.