The Effect Of Microwave Irradiation On Stered Grain Pests

Effect of microwave irradiation produced by microwave oven on different stages of Tribolium castaneum (Herbst),Oryzaephili surnamensis (Linnaeus),Cryptolestes turcicus (Grouville),Sitophilus oryzae (Linnaeus),Sitophilus zeamais (Motschulsky)and Rhyzopertha dominica (Fabricius)were bio-assayed. The output power was adjusted to 160 W, 320 W, 480 W, 640 W and 800 W by the oven controller and the irradiating time was in 5 s, 10 s, 15 s, 20 s,25 s and 30 s, respectively. And the irradiation with the power of 160 W, 320 W, 480 W, 640 W, 800 W was carried out in 20 s and with the power of 800 W were done in the time of 5 s, 10 s, 15 s, 20 s and 25 s for the test inscets which were mixed in the flour,rice or wheat relatively.The results showed that: the mortality rate of the test pest increased with the extension of irradiation time under the same microwave power, and the insect's death increased with the increasing of microwave power under the same irradiation time. The different states of the powder feeding insect pests were exposed to microwave radiation directly, the pupae and eggs showed strong tolerance , while the larvae was the most sensitive stage. The sensitivity of boring bettle from high to low were: egg, larva, pupa and adult which was analyzed by the method of microwave treatment.The microwave treatment had been taken to treat the different states of Tribolium castaneum which mixed in the flour and the Oryzaephili surnamensis mixed with the rice, when the power was 800 W and irradiation time of 25 s, the four stages of the pest could be eliminated completely . And the pupae showed a stronger tolerance. The five stored grain pests in wheat had been treated by microwave irradiation and found that the sensitivity of the five pest from high to low were: Oryzaephili surnamensis,Tribolium castaneum,Sitophilus oryzae,Rhyzopertha dominica and Cryptolestes turcicus. And the mortality rate of pests had a direct proportion with moisture content of the wheat sample.After microwave treatment, the fatty acids of flour and rice decreased slightly, with the time of microwave treatment increased,utill the 15th day and 30th day ,the measurement of free fatty acids increased first and then reduced,the fatty acid value between the flour and rice which were treated by the microwave and the untreated was not significant , the wheat samples had been treated by the microwave , the extension of irradiation time under the same power or under the same irradiation time to increase the power, the wheat germination.rate reduced accordingly.Under the lethal dose, the germination rate of wheat samples varied from 97% -67%.