Jiang N, Schulthess F
Stemborer Biological Control Project, International Centre of Insect Ecology and Physiology, PO Box 30772 00100, Nairobi, Kenya.
Bull Entomol Res. 2005 Dec;95(6):495-504. doi: 10.1079/ber2005381.
Laboratory and field trials were conducted to evaluate the effect of plant species (maize, sorghum), plant age (young, middle, old) and four different nitrogen fertilization levels (N0-N3) on the bionomics of the invasive crambid Chilo partellus and the performance of its braconid larval parasitoid Cotesia flavipes. Plant N varied significantly between N0 and N1-N3, but the differences among the latter were not significant. Intrinsic rates of increase and net-reproductive rates of C. partellus followed the same trends: they were lowest with N0 and similar among the other treatments. On maize only, mortality of C. partellus and parasitism by C. flavipes tended to decrease with age of the plant while the percentage of borers reaching adulthood (i.e. pupation) increased. Borer mortality and parasitism was lower and pupation higher on sorghum than on maize. On both host plants, percent dry matter content of frass, which could affect ingress of the parasitoid into the borer tunnel, did not vary with nitrogen level but varied with age of the host plants: on maize, it was highest on young plants and on sorghum on old plants. Tunnels were shorter on young maize and sorghum plants; longer tunnels on older plants indicated compensatory feeding by the larva as a result of lower nutritive value of the food source. Consequently, larval weight was lower on older than younger plants. The level of nitrogen fertilization had no effect on food conversion efficiency of C. partellus. Nitrogen did not affect number of C. flavipes progeny while egg load of progeny increased significantly with nitrogen level, on both plant species. Differences in egg load between sorghum and maize were mostly not significant. It was concluded that on depleted soils only, an increase in nitrogen via mulching, rotation with a leguminous crop or fertilization would increase survival of C. partellus on both maize and sorghum and an increase in acreage of maize and in application of nitrogen fertilizer in an area would also increase the parasitism of C. flavipes.
开展了实验室和田间试验，以评估植物种类（玉米、高粱）、植株年龄（幼龄、中年、老龄）以及四种不同施氮水平（N0 - N3）对入侵螟虫小蔗螟生物学特性及其幼虫茧蜂寄生蜂黄足盘绒茧蜂寄生表现的影响。N0与N1 - N3之间植株含氮量差异显著，但N1 - N3之间差异不显著。小蔗螟的内禀增长率和净繁殖率呈现相同趋势：在N0处理下最低，其他处理间相似。仅在玉米上，小蔗螟的死亡率和黄足盘绒茧蜂的寄生率随植株年龄增长而降低，而蛀茎螟发育至成虫（即化蛹）的百分比增加。高粱上的螟虫死亡率和寄生率低于玉米，化蛹率则高于玉米。在两种寄主植物上，可能影响寄生蜂进入螟虫隧道的粪便干物质含量百分比，不随氮水平变化，但随寄主植物年龄变化：在玉米上，幼龄植株最高；在高粱上，老龄植株最高。幼龄玉米和高粱植株上的隧道较短；老龄植株上的隧道较长，表明幼虫因食物源营养价值较低而进行补偿性取食。因此，老龄植株上幼虫的体重低于幼龄植株。施氮水平对小蔗螟的食物转化效率没有影响。氮对黄足盘绒茧蜂后代数量没有影响，但在两种植物上，后代的卵负载量均随氮水平显著增加。高粱和玉米之间的卵负载量差异大多不显著。得出的结论是，仅在贫瘠土壤上，通过覆盖、与豆科作物轮作或施肥增加氮含量，会提高小蔗螟在玉米和高粱上的存活率，在某一地区增加玉米种植面积和氮肥施用量也会提高黄足盘绒茧蜂的寄生率。
