Effects of Low Temperature Acclimation on Developmental Stages of Stored-product Insects 1

Abstract

We studied low temperature acclimation by 4 immature age groups (21–24, 14–17, 7–10 or 0–3 days after oviposition), by adults from laboratory-cultured strains, and by a field strain of each of 3 species: Sitophilus oryzae (L.), rice weevil; Sitophilus granarius (L.), granary weevil; and Rhyzopertha dominica (F.), lesser grain borer. Insects were acclimated for 3 days at 21.1, 7 days at 15.5 and 7 days at 10.0°C, then placed in 4.4°C 2, 4, or 6 weeks. Non-acclimated samples were placed directly in 4.4°C. Prior acclimation increased survival of all insects at 4.4°C. The most cold-tolerant rice weevils and granary weevils were those of 14–17 days development, and most tolerant lesser grain borers, of 21–24 days. More granary weevil adults from the field strain than from the laboratory strain survived. Granary weevil adults (field or lab) were more cold-tolerant than adults of the other 2 species. The least cold-tolerant stages of all species were 0–3 days development (eggs).