防治小包裝米害蟲方法之評估

Abstract

為解決小包裝米受積穀害蟲嚴重為害問題，本試驗實際進入米商的碾米廠進行取樣及試驗，發現米象（Sitophilus oiyzae (L.)）已逐漸成為稻穀中積穀害蟲的優勢種，族群密度遠高於以往在農會委託倉庫中之調查結果，且可能是小包裝米中主要害蟲來源。在銷售階段，於室溫環境儲藏三個月後，小包裝糙米每公斤內發生米象活蟲數高達126隻。於溫控超市內，小包裝米袋內溫度約較室溫環境低3℃ ，但蟲數卻明顯下降，儲藏三個月後僅159隻，兩者相差79倍。防治上再配合無毒物質矽藻土的使用，將矽藻土與糙米以1:200的比例混拌，在溫控的超市中儲藏三個月後每公斤糙米內活蟲數更降低至8隻。運用溫控且添加矽藻土於白米中，可將米象蟲數從每公斤中143隻降低至2隻。銷售環境溫度的降低，不只降低蟲數，更延緩害蟲發生，如配合添加矽藻土可使防蟲效果更顯著。未來結合溫控與混拌矽藻土的綜合防治，將可實際解決小包裝米嚴重的蟲害問題。 In order to solve problems caused by stored-product insects affecting commercial rice in small packages, rice in storehouses at mill factories was sampled and was subjected to a series of tests in this experiment. It was found that Sitophilus oiyzae was the dominant pest among stored-product insects during rough rice storage in these mill factories. S. oiyzae population densities in this study were much higher than any that had been previously reported from Farmer’s Association bins in earlier studies. These large populations might be the major source of S. oiyzae found in small packages of commercial rice. Among packages on store shelves, an average of 126 live S. oiyzae could be found in a 1-kg package of rice after storage for 3 months at room temperature (RT). However, in air-conditioned environments, about 3 t lower than RT, only 15.9 S. oiyzae could be found, an almost 8-fold decrease. With the addition of diatomite (w w, 1 200) in small packages of brown rice in air-conditioned supermarkets, S. oiyzae could be suppressed to only 8 bugs/kg of rice. In the case of milled rice under the same conditions (combining air-conditioning with the application of diatomite), the number of S. oiyzae could be reduced from 143 to 2 bugs/kg of rice. These results show that lower temperatures can dramatically reduce the number of S. oiyzae occurring in rice and delay the development of these pests when the rice is treated with diatomite. The combined use of air-conditioning and diatomite supplementation may be an effective integrated pest management strategy to solve the severe pest problems in small packages of commercial rice in the future.