Post-harvest treatments to reduce emergence and damage caused by larvae of Curculio sayi (Coleoptera: Curculionidae).

Damage caused by lesser chestnut weevil (Curculio sayi Gyllenhal) larval feeding affects yield and marketability of chestnuts (Castanea spp.) produced by commercial growers and hobbyists across the eastern United States. Post-harvest treatments to mitigate weevil damage involve submerging chestnuts in heated water for ≥20 min. Prolonged submergence in hot water, however, can discolor chestnuts or diminish quality of chestnuts in cold storage. We assessed larval emergence from chestnuts held at room temperature (controls), or submerged in water at 22.5°C (unheated), 43.3°C, 49.0°C, 54.4°C, or 60°C for periods of 5 to 30 min. Subsets of treated chestnuts were quartered after submergence, then again following 30, 60, or 90 d of cold storage (1°C) to evaluate larval feeding damage, chestnut quality and storability. Effective control (less than 1 emerged larva per 100 chestnuts) corresponded to submergence for 15 min in 49°C water, 10 min in 54.4°C water or 5 min in 60°C water, while 24 to 41 larvae per 100 chestnuts emerged from controls. Quality of chestnuts in cold storage declined sharply for chestnuts submerged in 54.4°C water for 25 min or 60°C water for 20 to 25 min. Submerging chestnuts for 10 to 20 min in 54.4°C water appeared optimal; no larvae emerged and chestnut quality was retained for 60 d in cold storage. Time needed to attain core temperatures lethal to weevil larvae varied with chestnut size. Curatura (water curing) and exposure to alternating cycles of warm and cold temps were also evaluated.