Biology of broadbean seed beetle ( Bruchus rufimanus ; Coleoptera: Chrysomelidae) in Latvia

Abstract

The broadbean seed beetle (Bruchus rufimanus Boheman, 1833) is a major pest of faba bean (Vicia faba L.) almost everywhere this crop is grown. The main tasks of this research were to study the seed beetle's phenology, and rates of egg laying, larval survival and the emergence of young adults before the harvest. Studies were done in field conditions in farms located in various places in Latvia. The highest density of imagines was observed at a time when the plants were flowering intensively. Egg laying began as soon as the pods had formed in the lower third of the stem and lasted 4–5 weeks. In severe infestation happened, more than 34 eggs were laid per pod. The percentage of damaged yield increased in proportion to the average number of eggs laid on pods until this number reached 11–12 eggs per pod and remained at approximately the same level also when egg-laying rate was higher. In several fields, no seeds with imago exit holes were found in the samples few days before harvest, while in other sowings, the proportion of such seeds exceeded 90% of the total amount of damaged yield.