Studies on feeding characteristics of grassland caterpillar Gynaephora menyuanensis and its economic threshold for control in Qinghai
In order to elucidate the feeding habits of grassland caterpillar Gynaephora menyuanensis in Qinghai and establish its economic threshold for prevention and control,the G. menyuanensis feeding preferences and its feeding ability on eight plant species were observed under indoor conditions. Cages enveloping tests were conducted using different population densities,and the control effects of different biological agents against G. menyuanensis were also analyzed. We calculated the economic threshold of G. menyuanensis by considering factors such as the price of pasture,level of yield,and prevention cost,providing theoretical basis for the prevention and control of G. menyuanensis. The results showed that among the eight selected plant species,G. menyuanensis preferred for needle fescue Stipa capillata and pendulous lancelet Elymus nutans,with relative feeding frequencies of 0.33 and 0.26,respectively. The highest daily feeding amount (40.67 mg/d) was recorded for the 4th instar larvae,and the 5th instar lar-vae showed the highest utilization and conversion rates on needle fescue,at 6.61％ and 93.94％,respec-tively. A regression model relating density (x) and forage yield loss (y) yielded the linear function y=0.051x+0.083 (R2=0.940),which was the best fit. The results of field control showed that,10 d post-ap-plication,a mixed treatment of Beauveria bassiana and Metarhizium anisopliae achieved the highest control effect at 98.92％,followed by the application of M. anisopliae alone at 97.33％. The economic thresholds for the control of G. menyuanensis were 49.35-57.00 individuals/m2 for Bacillus thuringien-sis Ps3 alone,45.43 individuals/m2 for B. thuringiensis alone,54.25 individuals/m2 for C. albicans,and 90.92 individuals/m2 for a mixed treatment of M. anisopliae and B. bassiana. Since the 3rd instar larvae had the lowest feeding rates,considering the cost of control and control effect,it is recommended to ap-ply M. anisopliae for field control before the larvae reach the 3rd instar.
万方数据
维普
