关键词: 豆科牧草, 种子产量, 产卵, 生活史, 越冬

Abstract: Alfalfa seed chalcid (Bruchophagus roddi) is an important insect pests in milk-vetch (Astragalus adsurgens) as it bores into seeds, and seriously affects the yield of viable seed. In order to obtain relevant information for timely control and reduction of this pest, in this study mature inflorescences (early flowering, EF) and immature inflorescences (late flowering, LF) were collected from 8 regionally sourced germplasm lines (Inner Mongolia, Guyuan, Ningxia, Liaoning, Shanxi, Ordos, Henan, Zhongsha) of A. adsurgens, beginning in early November when plants were at a mature stage of growth. Three inflorescences of each variety were enclosed in nylon bags with fine mesh and placed outdoors in order to capture and count emerging adults. At the same time, seeds of each enclosed inflorescence were harvested and put into glass petri dishes in the laboratory at room temperature. The number of emerging adults in each treatment were then counted weekly, until no further emergence of adults occurred. The objectives of these tests were to determine the timing of emergence of B. roddi and the levels of parasitism of different varieties and different categories of spikes. The percentage of parasitized seeds ranged from 0 in late flowering inflorescences of the Liaoning line, to 20.71% in early flowering inflorescences of the Guyuan line. Generally, parasitism of late flowering inflorescences was low. Only the Shanxi line had significant parasitism of late flowering inflorescences, while the Ordos line was notable, compared to other lines, for low parasitism of early flowering inflorescences. The emergence timing of B. roddi differed between the indoor and outdoor samples with adults first appearing on February 3rd and May 5th, respectively (91 day difference); and peak emergence on March 31st and May 26th, respectively (56 day difference). Hence, the indoor adult emergence period lasted for 167 days, while the outdoor feathering lasted only 77 days. However, the date of complete emergence for both indoor and outdoor conditions was all on July 21st. There were two emergence peaks in both EF and LF inflorescences, indicating that the B. roddi in the collected spikes had two egg-laying periods. In addition, emergence timing differed between varieties meaning that the date of egg-laying was affected by the plant variety. In conclusion, the larvae of B. roddi have no winter dormancy, and can continue to grow, feed, and develop to adults as long as the temperature is appropriate. All the emerging adults counted, both indoors and outdoors, would have been able to fly and attack other plants in the field. It is concluded that the optimal time to control B. roddi adults in A. adsurgens field crops would be from the beginning of flowering to late July.

Key words: Leguminous forage, seed yield, lay egg, life history, overwintering