Study On The Development And Predation Of Cheyletus Malaccensis (Oudemans) At Different Temperatures

As an important class of predator,predatory mites play a big role in the biological control and economic significance.As an important commodity related to national economy and people's livelihood,the grain has the characteristic of large reserves and long storage period.Pest control is the key point of daily management of grain storage.With the problem of resistance and environmental pressure caused by chemical fumigation,the integrated control technology has become the focus of research.The basic biological characteristics,reproduction and development of Cheyletus malaccensis?Oudemans?reared on Acarus siro,were studied at different temperatures.Age-stage,two sex life tables and predation rate analysis of C.malaccensis fed on A.siro at different temperature were constructed,on basis of two sex life table theory and predation analysis.The major contents are as follows:1 Effects of temperature on the growth and development of C.malaccensisThe development of C.malaccensis?Oudemans?fed on A.siro were observed by individual rearing under six constant temperatures of 15-32?and 75%RH.The results showed that the developmental duration of C.malaccensis?Oudemans?was shortened gradually with the increasing of temperature at the temperature range of 15-32?.According to the priority law,the developmental threshold of all stages of C.malaccensis are similar range from 11.47-13.60?.Based on the Wang-Lan-Ding model,the development rates fit well with the temperatures.Fitting results showed that the optimum developmental temperature was 26.26-29.99??female?,28.12-19.97??male?,the critical lethal high temperature was 34.69-39.92??female?,32.28-39.55??male?and the critical lethal low temperature was 4.42-14.82??female?,6.73-14.61??male?,with five period of C.malaccensis range from egg to adult while the males had four period.The results can be inferred that raising a certain development temperature is helpful to shorten the development time of C.malaccensis.Considering the development duration,fecundity and the difference between males and females,the optimum temperature for raising C.malaccensis is 24-28?.Based on the critical temperature of C.malaccensis,it can establish the population under the temperature conditions in most ecological regions of China when used as a natural enemy.2 Age-stage,two-sex life table constructions of C.malaccensis fed on A.siro at different temperaturesBased on the two-sex life table theory and analysis technology,age-stage two-sex life table of C.malaccensis fed on A.siro was constructed at the temperatures range from 22 to 32?and 75%RH.The results showed that within a certain temperature range,the mean generation time and life expectancy of C.malaccensis decreased gradually with the increase of temperature,with the lowest was 12.49 d and 22.15 d at32?,respectively.The net reproductive rate and fecundity were the highest at 28?,which was 290.25 and 544.52,respectively.The intrinsic rate of increase raised with the increase of temperature.The finite rate of increase showed the same trend.The female age-specific fecundity?1?₄)and age-specific fecundity of total population?8?)increased firstly and then decreased within the experimental temperature range.The peak value of the two curves was 28?>24?>30?>32?>22?.28?was a optimum growth and development condition for the multiplication of C.malaccensis.3 Predatory rate analysis of C.malaccensis to A.siro at different temperaturesBased on predation analysis,the predation of C.malaccensis to A.siro at different stages was studied at the conditions of 22,30 and 32?and 75%RH.The results showed that the daily predation rate of C.malaccensis to A.siro at three temperatures increased firstly with age and then decreased.The daily predation rate of C.malaccensis to A.siro at 32?was the highest value of 20.Meanwhile,the age-stage specific predation rate of C.malaccensis to A.siro reached the highest values of 17,15.67 and 20 on 27,18and 6 d,respectively at the temperatures of 22,30 and 32?.The age-specific predation rates increased wavily with age at different temperatures,and the order from high to low was:32?>30?>22?.The cumulative net predation rates from high to low were 22?>30?>32?and the transformation rates were 30?>22?>32?.The results showed that increasing the temperature properly is helpful for the predation of C.malaccensis to pests.The predation rate at 32?was the highest while the cumulative net predation was the lowest,and the predation rate at 22?was the lowest while the cumulative net predation was the highest.The adults of C.malaccensis with the highest predatory ability had a short developmental duration and a low cumulative net predatory rate when applied in high temperature ecological areas.Supplementary insertion of C.malaccensis is a better biological control strategy.