Population Dynamics and Probit Models of Adult Cephus fumipennis (Hymenoptera: Cephidae)

Author of the article:ZHAO Li-Min, JIA Hao, YANG Rong-Ke

Author's Workplace：Shaanxi University of Technology

Key Words：Cephus fumipennis; occurrence period; probit model; forecast

Abstract：The gray-winged wheat stem sawfly, Cephus fumipennis Ev. is a key insect pest on spring wheat in Northwestern China. To explore its bionomics and control techniques, the authors made systematic observations on growth and decline trends of adults in spring wheat fields, and simulated the observed data with a linear correlation and regression analysis between probits and dates. The results indicated that the probits for adults were closely correlated with the observational Julian dates; several probit models were established wherefrom; the chi-square goodness-of-fit test showed that the aptness of all the models was higher than 0.99; the curves of adult increments followed a normal distribution on the dates. Based on the models, the authors estimated and forecasted adults' peak days, peak periods, appearing periods, and related 95% confidence intervals at the three observational sites. At the site in Minhe County where the altitude was 1,820 m, the theoretical peak period was from May 23 to June 4; in Xunhua County, 1,800 m, from May 23 to June 2; whereas in Huangzhong County, 2,760 m, from July 3 to 20. At each site, the appearing period was twice as long as the peak one, and both periods were bilateral symmetry on the peak day. The probit models and the analytical methods would be applicable in forecasting of other insect occurrences.