Biology of Bruchus dentipes Baudi (Coleoptera: Bruchidae) on Vicia faba and a method to obtain gravid females during the imaginal quiescence period

Abstract

Bruchus dentipes Baudi was found to have four larval instars, and the sex ratio was very close to 1:1. Both sexes fed on pollen and nectar of faba beans (Vicia faba) for seven days before and throughout the oviposition period of the females, which was about 33 (range 26–40) days. The beginning and peak of oviposition were influenced by the phenology of the crop, particularly flowering and pod-setting dates, but also temperature. Females laid an average of 123 (range 28–310) eggs, and the end of the adult life in the field came in May when the pods had matured. In different years, peak oviposition occurred on different dates in April when the pods were still all green. During the quiescence period in the winter, females obtained from wetted seeds were fed with different diets in the laboratory, but only those supplied with faba bean flowers laid eggs. No major adult mortality occurred in seeds harvested in May and stored until the end of March of the following year, after which mortality rose steeply till all adults had died by early June. Therefore, storing seeds and delaying their planting till the following year will ensure 100% adult mortality. As the seeds remain viable, such storage is one method for reducing infestation in the field. Mortality of larvae in the stored seeds was from cannibalism when two larvae met at the same tunnel (10%), from the mite Pyemotes tritici (Lagrèze-Fossat & Montagné) (11%), from the braconid larval parasite Triaspis thoracicus (Curtis) (2%) and from unknown reasons (5%).