大造桥虫幼虫生长发育及其取食规律的初步研究

Preliminary Study on Growth and Feeding Amount of Ascotis selenaria Larva

大造桥虫是危害大豆的主要食叶性害虫之一。为了明确大造桥虫幼虫发育龄期及各龄期对大豆叶片的取食量,深入研究其取食危害规律,采用离体叶片单头饲养法,系统观测幼虫生长发育及各龄期取食量。结果显示,大造桥虫幼虫共6龄,在27～28℃条件下,幼虫发育历期平均需要19.05 d,其中1龄3.07 d,2龄2.00 d,3龄1.86 d,4龄2.24 d,5龄3.33 d,6龄6.38 d。各龄幼虫的头宽与体长均随着龄期的增长而增大,头宽与体长的生长模型分别为y1=0.178e0.489x(R2=0.997)和y2=1.671e0.519x(R2=0.994);大造桥虫幼虫发育阶段与取食量的关系模型为:叶面积,y1=6.387e1.202x(R2=0.976),鲜叶重,y2=0.467e1.319x(R2=0.949)。整个幼虫期可累计取食大豆叶片面积为17 218.88 mm2,重量为2 669.50 mg。其中4～6龄幼虫的取食量占整个幼虫期取食量的98%以上。因此,从有效控制大造桥虫幼虫危害的角度出发,防治宜在3龄前进行。

It is necessary to research defoliator development and the feeding law in order to estimate the developmental stage of defoliator in the field,forecast the extent of their damage and establish the prevention strategy scientifically.Ascotis selenaria is a kind of important defoliator pests of soybean.Up to now,there is no consistent conclusion on its feeding amount and instars.In this experiment,the development and feeding amount of Ascotis selenaria were observed systematically using the method of single larvae fed by detached leaves.The results showed that Ascotis selenaria larvae undergo 6 instars at temperature of 27℃-28℃ and the average developmental duration of larva was 19.05 days.The instar from 1to 6 instar was 3.07,2.00,1.86,2.24,3.33,6.38 d,respectively.Head width and body length were both increasing with the instars,the growth equation as follows：head width y1=0.178e0.489x（R2=0.997）;body length,y2=1.671e0.519x（R2=0.994）.Total feeding amount of Ascotis selenaria larva was 7 218.88 mm2 and about 2 669.50 mg.The relationship between developmental duration and feeding amount is：leaf area,y1=6.387e1.202x（R2=0.976）;leaf weight,y2=0.467e1.319x（R2=0.949）.The 4th-6th-instar larva＇s feeding amount account for more than 98% of the whole larva duration.