Host Selectivity Of Dysmicoccus Neobrevipes (Beardsley) And Its Mechanism

The selectivity of Dysmicoccus neobrevipes (Beardsley) on Agave sisalana, Agave Americana, Musa balbisiana, Opuntia dillenii, Acacia pycnantha, Euphorbia longana and Cocos nucifera was studied in this paper. The effect of A. sisalana, A. Americana, M. balbisiana and O. dillenii on development and reproduction of D. neobrevipes was researched. The major chemical consistents of leaves of seven host plants were tested. The influence mechanism of selectivity of D. neobrevipes on different host plants were discussed by correlation analysis. The main findings were as follows:(1) Under the free selection, D. neobrevipes had frequent activities within 24 hours, slowed down after 48 hours and was inaction without external interference after 72 hours. The selection sequence of D. neobrevipes on host plants was shown to be A. sisalana> A. Americana> M. balbisiana> O. dillenii> A. pycnantha>E. longana> C. nucifera. Under the non-free selection, there were significant differences among all host plants. A. sisalana was the most suitable. A. pycnantha, E. longana and C. nucifera were not the optimum host plants.(2) The developmental time of D. neobrevipes reared on O. dillenii was the longest, but had the shortest development on A. sisalana, it was shown to be 115.85 d and 69.77 d, respectively. The life-span of D. neobrevipes on A. sisalana was shown to be 58 d, and the number of eggs laid was 246. The longevity of D. neobrevipes on E. longana and A. pycnantha was 47 d and 36 d, respectively. Opuntia dillenii had the shortest longevity and the lowest eggs laid. The population index of D. neobrevipes was as following:A. sisalana>M. balbisiana>A. Americana>O. dillenii.(3) To study the alternative mechanism of host plants. The relative contents of tannic acid,soluble sugar and soluble protein of host plants were determined. The chemical concentration and the selection number of D. neobrevipes were correlatively analyzed. The relative contents of tannin acid,soluble sugar and soluble protein had the most significant difference among different host plants. The selection number of D. neobrevipes and the content of tannin acid had extremely significant negative correlation (P<0.01). The content of soluble sugar had the positive correlation, but was not significant differerce. The content of soluble protein had the most significant positive correlation.(4) There were no occurrence of adults during January or September. A peak period was found from March to April and November to December. The generation overlapping was occurred, five generations per year. The first, second, third, fourth and fifth generation was occurred from late February to early March, from late May to early June, from in late July to early August, in early October and early December, respectively.