Research On Captive Breeding And Analysis Of The Pest Control Effects Of Coccinella Transversoguttata F.

Coccinella transversoguttata F.is one of the main dominant predatory insects in Tibet,with wide distribution and large population size,and has the advantages of early appearance and long feeding time as the main natural enemy of crop pests,which can be applied to the biological control of aphids.However,there are few studies on their biological characteristics,geospatial distribution and predatory responses,and they are not widely used.Since barley,oilseed rape and pepper are severely infested by aphids in Tibet,three aphids frequently found on barley,pepper and oilseed rape,Schizaphis graminum,Myzus persicae,Brevicoryne brassicae,were selected as natural fodder in this experiment.Through individual feeding,predation effect of C.transvorogutata at different aphid densities,disturbance response at different ladybug densities and artificial feed ration experiments,we studied the feeding and pest control of C.transvorogutata and laid the foundation for further use of C transvorogutata to control pest damage and factory breeding of C.transvorogutata.The main research results are as follows:（1）The results of the study on the effect of different aphids on the growth of the C.transvorogutata showed that the S.graminum was more favorable to the growth and development of the C.transvorogutata and the population expansion of the B.brassicae was relatively poor.The developmental period of C.transvorogutata reared with each aphid was from longest to shortest:B.brassicae（20.8 d）>S.graminum（18.3 d）>M.persicae（18.0 d）;the survival rate of feeding S.graminum and M.persicae was 55%and 50%,respectively,which was significantly higher than that of feeding B.brassicae（30%）;the nymphal weight of feeding S.graminum and M.persicae was 0.034 g and 0.033 g,respectively,which was significantly higher than that of feeding B.brassicae（0.020 g）.The body length was 7.46 mm and 7.26 mm for wheat and M.persicae,respectively,significantly higher than that of 6.25 mm for B.brassicae;the body width was 4.95mm for S.graminum,significantly higher than that of 4.63 mm for M.persicae and 4.57 mm for B.brassicae;The highest egg production in the first 10 days（328 eggs）was in the C.transvorogutata fed on the S.graminum,and the lowest egg production in the first 10 days（283 eggs）was in the C.transvorogutata fed on the B.brassicae.（2）The results of predation effect of C.transvorogutata at different aphid densities showed that the predation of M.persicae and B.brassicae by C.transvorogutata was significantly higher than that of S.graminum.The predation on the three aphids by each insect state increased with the increase of aphid density,and the predation on the aphids by the C.transvorogutata basically stabilized when the aphid density reached a certain level,and this result was consistent with the Holling II model.The a’/Th values of each insect state of the C.transvorogutata on the three aphids as a whole were in the order of 4th instar larvae>adult females>adult males>3rd instar larvae>2nd instar larvae>1st instar larvae,in which the C.transvorogutata had the strongest control over M.persicae and the weakest control over S.graminum.（3）The results of the study on the intraspecific disturbance effect and searching effect of C.transvorogutata at different densities showed that the higher the density of C.transvorogutata,the lower the average predation rate per ladybug beetle,and when the density of C.transvorogutata increased from 1 to 5 heads/dish,the average predation rate decreased to 0.188,0.187 and 0.142,respectively.the mathematical models of disturbance response of C.transvorogutata to predation on S.graminum,M.persicae and B.brassicae The mathematical models of the disturbance responses of the C.transvorogutata to the predation of the S.graminum,M.persicae and B.brassicae were E=0.308P^-0.691,E=0.427P^-0.458and E=0.314P^-0.482,respectively,and the comparison of the parameters showed that the disturbance constant m（0.458）of the M.persicae was the smallest and its intraspecific disturbance effect was the smallest,while the disturbance constant m（0.691）of the S.graminum was the largest and its intraspecific disturbance effect was the largest.In the comparison of the same age of the C.transvorogutata,the smaller the aphid density the higher the finding effect of the C.transvorogutata,and the finding effect decreased with the increase of the aphid density.In the range of aphid densities set,the overall finding effect of each insect state of C.transvorogutata was the highest for M.persicae and the lowest for B.brassicae.（4）The effect of different nutritional ratios on the growth and reproduction of lady beetles was tested by feeding the 1st instar larvae with three formulations of artificial feeds,and all 1st instar larvae of lady beetles died on the second day of feeding in two replications.The research on the artificial feed of lady beetle still needs to be continued.This study clarifies the effects of different aphids and artificial diets on the maintenance and promotion of C.transvorogutata,and the investigation of the effects of different ratios of rearing C.transvorogutata growth.This is an important practical guidance for the development of large-scale artificial rearing and release application technology of C.transvorogutata.