| The pink hibiscus mealybug, Maconellicoccus hirsutus(Green), is a polyphagous sap-sucking pest with a great threat to fruiter, vegetables and crops and it has been listed as quarantine pest in many countries which import agricultural products of China. As a new pest found on soyabean, it also has a potential threat to the safety production of soyabean and it’s intercropping of maize and cotton which is host of M.hirsutus in southern China because soybean intercropping with maize, cotton, wheat, cassava and sugarcane has becomming popular. So in this paper, we carried out a systematic study on the morphological characteristic, habitus, developmental durations, developmental threshold temperature, effective accumulated tempeature of this pest. Meantime, the life table of the laboratory population fed on soyabean was constructed at different temperatures(16, 19, 22,25,28,31,34℃) to provide a valid experimental evidence and theoretical basis for this pest. The results were as follows:1. The morphological characteristics and biological habits of each instars were observed and described.There were five stages(egg, 1st, 2nd and 3rd instar nymph and adult) in the life cycle of female; while in male, there were six stages(egg, 1st and 2nd instar nymph, prepupa, pupa and adult). Length and width of each stage, number of antenna segments and surface secretion could be used to distinguish the differences between each instars or developmental stages.2. The observed results of individual development showed that the duration of the egg was 7.15 days. The nymphal stage of the female lasted 17.6 days and the female adult life was 29.97 days and the generation lasted 54.27 days at temperature of 25℃, soyabean as host. The 1st and 2nd nymphal stage of the male lasted 11.87 days, prepupa 2.27 days, pupa 3.33 days, the male adult life was only 3.37 days and the generation lasted 28.43 days.3. Temperature had a significant effect on the development of M. hirsutus at constant temperature 16~34℃ range, the developmental duration shortened as the temperature rised gradually.The female generation was 126 days at the temperature 16 and 40.37 days at 34℃ ℃. The male generation was 110.77 days at 16 and 22.87 days at 34 which had a more obvious ℃ ℃change.The effect of temperature was bigger on male than female. The developmental duration had great changes on male at the stage of egg, prepupa, pupa and adult when temperature changed, the same at egg and second instar on female.4. Temperature had a significant effect on the survival rate of M. hirsutus. The pink hibiscus mealybug had the highest survival rate and fecundity during the constant temperature 22~28℃, which was the optimum temperature range for the pest’s development. However the sustained higher and lower temperatures were unfavorable to their survival and reproduction.5. The temperature affected female reproduction significantly. The highest amount of spawning per female was 682 at the temperature of 22℃ and the minimum was 13 at the temperature of 34℃. The highest average spawning was 419.2 at 22℃ and the minimum was 28.0 at 34℃.6. Constructed life table of the experimental population of M. hirsutus at different temperatures. The population trend index(I) were larger than 1 at 16~31℃ and less than 1 at 34℃. With the temperature increasing, mean generation time shortened gradually and net reproductive rate presented a trend of rise first then fall. It showed that the finite rate of increase were larger than 1 which could mean the population growth with geometry number level. The observed value of intrinsic rate of increase and finite rate of increase were highest at 25℃. According to the relationship between temperature and intrinsic rate of increase deduced a regression equation r=-0.0008t2 +0.0418t-0.4496(R2=0.9717) to evaluate the rm was 0.1049. |
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