Development and Harmfulness of the Pea Weevil, Bruchus pisorum (L.), in the Forest-Steppe of the Middle Volga Region

This paper summarizes data on seasonal development and fecundity of the pea weevil Bruchus pisorum L., its impact on the chemical composition of the pea seeds, damage to seeds by the weevil larvae, pea productivity and resistance to the weevil, and also assessment of pest harmfulness depending on the pea farming techniques. Studies were carried out in 1989–2007 in the southern part of the forest-steppe zone (Samara Province, Bezenchuk and Kinel districts). The highest densities of weevils and of eggs laid on the forming pods were observed on determinate pea varieties with limited stem growth. Among the tested pea varieties, high resistance with less than 1% seed damage was observed in Selvay (USA), Usach Intensivnyi, and local varieties VIR 6559 (Afghanistan), VIR 2380 (Georgia), and Akhalkalaki (Georgia). Seed damage was higher in the years with less precipitation during the pea growing season (May–July). Seed damage in relatively large pods was 1.2 times as high as that in medium pods, and 1.9 times as high as that in small ones. The harmfulness of B. pisorum was determined by low field germination rates of damaged pea seeds, which was reduced by 44–85% as compared to that of intact seeds; the biological grain yield was reduced by 48–92%. The content of ash, protein, and tryptophan was higher while that of sugars, starch, lysine, threonine, alanine, aspartic acid, and serine was lower in damaged seeds than in intact ones. The ovipositing weevils preferred pea crops included in rotation with green manure, with regular and increased dosages of mineral fertilizers, and with presowing seed treatment with Tenso Cocktail or with Tenso Cocktail + Rhizotorphin; the difference was determined by better development of pea plants in the corresponding variants.