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Pea weevil (Bruchus pisorum) – pest management
The pea weevil, Bruchus pisorum, is a species widespread on all continents.
Description. The adult has an elongated, oval body, black, covered with thick pubescence, gray-reddish and it is 4-5 mm long. The egg is oval, white-yellow, 1.5 mm long and 0.6 mm wide. The newborn larva is 1.5-1.6 mm long, with thin legs, a brown head, and a yellow-reddish body. The last-stage larva doesn’t have any legs, is 5-6 mm long, and is colored in white-yellow. The pupa is yellow, 4-5 mm long.
Life cycle. The pea weevil produces one generation a year and overwinters in the adult stage in warehouses, infested grains, cracks in walls and floors. Some adults overwinter in the field, in infested grains, in the cracks of tree barks, or under plant debris.
At the end of April, when the average daily temperature exceeds 14º C, the adults migrate to the pea crops at distances of up to 3 km. The maximum flight activity is recorded at temperatures of 26-28 ºC, during the flowering stage of the pea crops and they remain very active during hot and sunny days, feeding on the pollen of pea flowers. When sexual maturity is reached, copulation and spawning take place. The spawning coincides with the formation of pods, begins at the end of May, and lasts approx. 30 days. A female lays 150-200 eggs, which are laid separately in well-developed pods (reaching up to 30 eggs in one pod).
After an incubation of 8-12 days, the newborn larvae penetrate through the wall of the pods in the beans, where they hatch and become larvae without legs. The development of larvae takes place inside the grains for 30-45 days. Even if several larvae have entered a bean, only one reaches full development.
Crop damage. The larvae gnaw the inside of the beans, forming ovoid “chambers”, consuming up to 40-50% of their mass. Adults feed on flower pollen.
Pest management. Specific insecticides must be used to treat the grains stored in warehouses.
Specialist's advice 
