南方根结线虫侵染对乌桕癞皮夜蛾幼虫生长发育和食物利用的影响

为明确南方根结线虫（Meloidogyne incognita）侵染对癞皮夜蛾（Gadirtha fusca）幼虫的影响是否因龄期而异，本研究以南方根结线虫侵染乌桕（Triadica sebifera），选用该植株叶片饲喂癞皮夜蛾大龄幼虫，以未受南方根结线虫侵染植株的叶片作为对照，比较不同龄期幼虫生长指标和食物利用指标的差异。结果表明：随着幼虫龄期的增加，癞皮夜蛾幼虫体质量、取食量及发育历期呈上升趋势；相对生长率呈下降趋势；食物利用率和食物转化率先上升后下降，而近似消化率则呈先下降后略微上升的趋势。线虫侵染处理后，与对照相比，癞皮夜蛾4龄幼虫的相对生长率、食物利用率和食物转化率显著提高；5龄、6龄幼虫的虫体质量和5龄幼虫的相对生长率以及6龄幼虫的取食量、近似消化率、化蛹率显著降低。南方根结线虫侵染对癞皮夜蛾幼虫生长及食物利用的影响因发育阶段而异，主要通过抑制两个末龄龄期幼虫的生长发育及化蛹，从而间接减轻癞皮夜蛾对乌桕的危害。

Effects of Meloidogyne incognita Infection on Gadirtha fusca larvae Growth and Food Utilization of Triadica sebifera

In order to examine whether effects of Meloidogyne incognita infection on Gadirtha fusca larvae vary with instars, the older larvae of G.fusca were fed by the leaves of Triadica sebifera infected by M.incognita, and the leaves of T.sebifera uninfected by M.incognita were used as controls.The differences in growth indexes and food utilization indexes of larvae at different instars were compared.The results showed that the larval biomass, the food consumption and the developmental duration of G.fusca gradually increased with the increase of larval instars.While the relative growth rate showed a downward trend.The food utilization rate and food conversion rate increased first and then decreased.While the approximate digestibility decreased first and then increased slightly.After M.incognita infection, the relative growth rate, food utilization rate and food conversion rate of the 4th larvae significantly increased compared with control group.The larval biomass of 5th and 6th larvae, the relative growth rate of 5th larvae, the food consumption, the approximate digestibility and pupation rate of 6th larvae all significantly decreased compared with control group.Effects of M.incognita infection on the growth and food utilization of G.fusca larvae varied with the developmental stage, mainly by inhibiting the growth and development and pupation of the two last instar larvae, the damage of G.fusca to T.sebifera was reduced indirectly.