Lethal Effects Of Heat Treatment On Four Kinds Of Stored Products Insect Pests

Southern cowpea weevil (C.chinensis L.),and cowpea weevil (C.maculatus F.),red flour beetle (Tribolum castaneum), and lesser grain borer (Rhyzopertha dominica) are four kinds of important grain insect pests, which are ditibuted all around the world.Can cause great lose of stored bean. The female lay eggs on the surface of the beans, after a very short period (just a few days), the larvae hatched into the beans. Southern cowpea weevil (C. maculatus F.) are alien species, Our coastal parts and border ports are often intercepted this pests insects. Tribolum castaneum, is an important pest in stored grain worldwide. and infest wheat, rice food and all kinds of flour products. Adult scent glands on the body secreted effluvium,which can cause food agglomeration,discoloration and mouldy taste and make the food lose of food value of grain. Rhyzopertha dominica is also a worldwide pest in stored grain,most in tropical and subtropical region,and is an important pest of stored wheat and other grains in southern China especially. This article is about heat treatment agains.Southern cowpea weevil,cowpea weevil,Tribolum castaneum Herbst and Rhyzopertha dominica at 42℃,46℃,50℃,54℃,58℃,60℃, the heat treatment time were 15min,30 min,45 min,60 min,75 min and 90 min, repectively. The result,showed corrected mortality changed whith the insect species,developmental period, temperature and heat treatment time. Adult moisture canten and protein canfeul were also measured in this paper.The research result provide some theretical data for using heat treatment to control these four kinds of stured grain insects.1.Heat treatment control on C. maculatusHigh temperature can control C. maculatus effectively for eggs, inside bean period (larva, pupa), adult stage. At 60℃and 58℃60 min, heat treatment the mortality rate can reach up to 100%. Even whith 15 min,30 min heat treatment when the adult C. maculatus, larvae and eggs mortality rate can reach up to 95%, The control effect of the heat treatment against pupal stage was not obvious, the mortality rate was 7.7% and 28%. However, with 60min heat treatment the processing time,mortality rate can reach 100%, which proved treatment of high temperature have better control effect on C.maculatus at relatively lower temperature 42℃and 46℃, whith 90min.treatment time, the carrected mertalities at different developmental stage was lower than 15%. The corrected murtalities keep the same level decreae whith the increasing treatment time from 15 min to 90 min.2. Heat treatment control on C.chinensisAt 58℃and 60℃, whith 30 min treatment time, the corrected mortalities of different stahe, of C. chinensis were 100%, and eveb whith 15 min,treatment time,the martalities were above 90%,whith showed high temperature had better contol against C.chinensis Hower, At relatively cower temperature 42℃,46℃and 90 min treatment time, the martalitie of all stages were below 12%.3. Heat treatment control on Tribolum castaneumTribolum castaneum adults and larvae of the two lower temperature 42℃and 46℃have a stronger tolerance to heat treatment at 42℃and 46℃and deal with 90min treatment time, the corrected mortalities were lower tan 10%; However,at 54℃,75mintreatment, the the corrected mortalities can increase up to 100%;At 58℃and 60℃100% mortality can be obtained with only 60 min.Treatment, which showed high temperature could contol triblium caotaneum offectively.4. Heat treatment control on Rhyzopertha dominicaThe larvae and adult, of Rhyzopertha dominica have string tolerauce on 42℃and 46℃heat 90 min treatnebt, the corrected murtalities were lower than 6%.However, at 58℃and 60℃, whith 60 min.Heat treatment, the mortalities,reachecl up to 100%. which showed these two temperature have better control on the larae and adults of 12 dorninica.5.The mechanism of of high temperature control on four stored product pestsHigh temperature on stored product pests are two mechanisms of death:First, severe dehydration temperature makes the insects, resulting in death; the second is the high temperature caused by the insect's own enzyme system has been damaged, modified coagulation proteins, leading to insects pests death.The moisture content (MC) of four kinds of stared product insect pests showed that the MC decereased as the temperature increased. MC deareased about 10% when temperture changed from 42℃to 46℃,which praved high temperature Led to dehyaration of insect and death.The protein content (PC) showed P. C. increased as temperature incereared from 42℃to 52℃and reached the highest at 52℃After 52℃,P. C. decreased gradually as temoerature increased. The reason is that stimulation of high temperature induced to generate heat shock protein,which made the P. C. higher. When high temperature lasted to increase protrin losed actioitions and denatured which resulted in insect pests death.