| Phenacoccus solenopsis Tinsley is a new invasive exotic pest which has been recently found in China, with a great potential threat to cotton, vegetables, ornamental plants and other cash crops of production. However, the reports about the mealybug were still confined to describe it’s occurrence, distribution, morphological and biology, lacking of comprehensive scientific research. So in this paper, we carried out a systematic study on the morphological characteristics, reproduction mode and environmental factors to understand the biological characteristics and provide a valid experimental evidence and theoretical basis for improving the prevention and control of this pest. The results were as follows:1. The life history of P. solenopsis and it’s morphological characteristics of each instars were observed and described. The results showed that there were five stages (egg,1st,2nd and3rd instar nymph and adult) in the life cycle of female; while in male, there were six stages (egg,1st and2nd instar nymph, pre-pupa, pupa and adult). Length and width of each stage, dark dorsomedial bare spots appearance, wax secretion conditions and number of antenna segments could be used to distinguish the differences between each instars or developmental stages. Moreover, at temperature of27±1℃, cotton as host, the mealybug develop rapidly; the nymphal stage of the female lasted15～20days and the total life span of the female was about47～59days, was much longer than male. Also, the insect had strong fecundity with an average egg laying amount per female adult ranging from400to500. 2. The studies on the reproduction mode of P. solenopsis had shown that all reproduction mode of the mealybug was gamogenesis, rather than parthenogenesis, and both male and female could be multi-mating. Under the tested conditions, the mated (including normal mated and delay-mated) female adult could normally lay eggs, while the unmated female adult could not, but with longer survival time. In addition, microscopic examination of the ovary structure and eggs development of the mated and unmated female adult showed that there were significant differences between the above two treatments.3. The development, reproduction and an analysis of the life table parameters of P. solenopsis feeding on three species of host plants:cotton, eggplant and tomato. The results showed that the pest could complete the whole generation development on the three hosts. Among them, the development, survival, fecundity and population growth were the best and fastest on cotton, followed by eggplant and tomato.4. Temperature had a significant effect on the development of P. solenopsis. At Constant temperature17～32℃range, the developmental duration shortened as the temperature rised gradually, and the developmental rate showed a significant positive correlation with temperature. While under condition of constant high temperature of37℃, the insect’s development was suppressed obviously and could not complete a whole life span. Moreover, the mealybug had the highest survival rate and fecundity during the constant temperature22～27℃, which was the optimum temperature range for the insect’s development, while the sustained higher and lower temperatures were unfavorable to their survival and reproduction. Furthermore, in a simulated natural environment of the summer high-temperature conditions (25～40℃), the insect’s development, survival and reproduction were faster and better.In summary, P. solenopsis has various advantage of biological characteristics to become a major invasive alien pest with not only a high fecundity, a wide host range, but also possessing strong environmental adaptability, so it can survive and multiply in most parts of China and may be a serious threat to cotton and other cash crops production. Therefore, it should be attached great importance to in-depth research, scientific prevention and control. |
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