Alfalfa flower midge

Systematic position: The Alfalfa flower midge (Contarinia constricta) belongs to the order Diptera and the family Cecidomyiidae. It is a highly specialized insect that specifically targets the reproductive structures of alfalfa, making it a significant pest in seed production systems.

Host plants and damage: The primary host is alfalfa (Medicago sativa). The damage is caused by larvae feeding inside the buds, which prevents normal pollination and seed set. Attacked buds swell, become distorted, turn yellow, and eventually die. A high infestation level can lead to nearly complete loss of the seed yield if not controlled effectively.

Biology and life cycle: The midge overwinters as larvae in cocoons within the soil. In spring, pupation occurs, and adults emerge in synchronization with the budding phase of the host plant. The female midge deposits eggs into the developing flower buds. The larvae grow inside these buds, and after completing their development, they drop to the ground to pupate in the soil, often completing multiple generations per season.

Agricultural control methods: Cultural practices are the first line of defense. This includes implementing crop rotation and maintaining spatial isolation between seed fields and older alfalfa stands. Timely mowing of the crop for green forage before the larvae drop to the soil is a highly effective way to break the life cycle and reduce the population density for the next season.

Chemical and integrated management: Chemical intervention is necessary when monitoring reveals high adult population density during the pre-blooming stage.

• Monitoring adults using yellow sticky traps.
• Application of selective insecticides targeting imago.
• Encouraging natural predators and parasitoids.
• Deep tillage to bury overwintering pupae.