Controlled ambient aeration during rice storage for temperature and insect control

Rice (cv. Cypress) was harvested in September 2000 from a farm near Grady, Arkansas, placed in six, 600-t (31,000-bu) bins [each was filled with similar to430 t (21,000 bu)], and dried gently from 18 to 13% moisture content (MC). Three of the bins were equipped with an aeration control system activated by specific ambient air conditions in three cycles. Three of the bins were aerated by the on-site, storage manager under his normal regimen. Grain temperatures were recorded at four locations within each bin. To monitor insect viability, small cages were filled with approximately 150 g of rice and 20, 1- to 2-week-old mixed sex adults of one insect species. The species that were tested included the lesser grain borer, Rhyzopertha dominica (Fauvel); the rice weevil, Sitophilus oryzae (L.); and the saw-toothed grain beetle, Oryzaephilus surinamensis (L.). Cages were removed at 5-week intervals, and surviving and emerging insects were counted. Grain temperatures were significantly reduced through controlled aeration relative to the traditional, manual aeration. In addition, both live insect counts and total emerged adult insects recovered from the cages were significantly lower (p < 0.05) within the bins treated with controlled aeration. The rice weevils were the hardiest of the insects tested, while saw-toothed grain beetles survived the least. This work indicates that controlled, ambient aeration can be an effective storage treatment against insects and may be a useful alternative to chemical controls.