Biology of Sawtoothed Grain Beetle (<I>Oryzaephilus surinamensis </I> L.) and Its Control Efficacy Using Ozone in Milled Rice

Abstract

Biology of sawtoothed grain beetle (Oryzaephilus surinamensis L.) reared in ‘Pathum Thani 1 rice was studied in 96-well plate held at  28-32 °C and 75% RH. It was found that egg incubation period was 2.71±1.60 days. The mean duration of the first instar to the fourth instar  were 2.42±0.97, 2.70±0.65, 2.74±0.90 and 3.31±0.80 days respectively. Prepupal and pupal periods were 1.10±0.3 and 5.92±0.67 days respectively. The total life cycle from egg to adult emergence was 19.81±1.65 days. The oviposition preference in various grains of sawtoothed grain beetle was examined. Barley and barley mixed with 5% yeast were the most preferred oviposition sites followed by Pathum Thani 1, Kum 88061, Kumdoisaket and Niaw San-pah-tawng 1, respectively. Barley and barley mixed with 5% yeast  were also the best food source for development of sawtoothed grain beetle. The efficiency of ozone to control sawtoothed grain beetle was investigated. Pupa was the most tolerant stage when exposed to 60 ppm ozone for 2 hours with mortality rate of 60.83±3.19%. The optimum time and concentration of ozone for controlling pupa of sawtoothed grain beetle were examined. Hundred percent mortality was found within 6 hours after exposing directy to 60 ppm ozone. However, when thirty pupae per one kilogram of KDML 105 rice were exposed to 60 ppm ozone for 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 14, 16, 18 and 20 hours, all pupae were died when exposing to ozone for 20 hours.