华北棉区第二代棉铃虫的经济阈值

1980—1983年在河北省饶阳县及安徽省濉溪县的不同的土壤肥力类型、不同的棉花品种和不同的栽培管理条件下进行了模拟为害和自然为害的试验,旨在确定第二代棉铃虫Heliothis armigera(Hübner)数量与棉花Gossypium hirsutum L.产量和质量的关系。试验结果表明,棉花对于第二代棉铃虫为害的补偿力很强,这种补偿力随着土壤肥力的提高而增强。棉花品种、年份以及栽培管理方法对补偿力的影响属于次要。通过组建的一个静态模型,收进了二代棉铃虫防治的直接收益与代价以及间接收益与代价,算得高、低肥力地的第二代经济阈值,百株累计卵量分别为332粒和34粒。产量水平在80—90斤的中等偏低肥力地,其阈值可定为60粒。

ECONOMIC THRESHOLDS OF THE SECOND GENERATION OF COTTON BOLLWORM IN NORTH CHINA

Field experiments were conducted at two localities in North China during four growing seasons (1980-1983) to determine the relationships between the population density of the second generation cotton bollworm, Heliothis armigera (Hubner), and cotton yield. The experiments comprised the simulated and real damage and took account on the effects of compensation at various levels of soil fertility, cotton varieties, and various cultural methods. The results show that cotton's ability to compensate for damage during early season (late June to early July) increased with soil fertility. The differences in the results between cotton varieties and between years as well as between cultural methods were less important. Consquently, the economic threshold is largely affected by soil fertility. Expressions of economic loss and number of eggs for various levels of fertility were given.A static economic threshold model was developed incorporating direct benefit and cost as well as indirect benefit and cost. And the economic thresholds were calculated to be 332 eggs per 100 plants for the rich soil, 34 eggs for the poor soil, and 60 eggs for the medium soil.