草地贪夜蛾对水稻和玉米的取食和产卵选择性与适合度

【目的】明确草地贪夜蛾Spodoptera frugiperda对寄主植物水稻和玉米的取食和产卵选择性与适合度,进而分析草地贪夜蛾对水稻的为害风险。【方法】采用自由选择法,测定草地贪夜蛾对水稻和玉米的取食、产卵选择性。调查取食水稻和玉米苗的草地贪夜蛾的生长发育、存活率、繁殖力的差异,用种群增长趋势指数(I)评价水稻对草地贪夜蛾的适合度。【结果】草地贪夜蛾对水稻和玉米的取食和产卵选择性存在显著差异。接虫后2-48 h,幼虫对玉米的取食选择率随时间延长而逐渐增加,而幼虫对水稻的取食选择率随时间延长而逐渐降低;接虫后48 h,2龄幼虫和4龄幼虫对玉米的取食选择率分别为93.06%和59.72%,分别是对水稻的取食选择率的66.95倍和21.48倍。自由产卵6 d,在玉米上的产卵量是在水稻上的8.64倍。与取食玉米苗的相比,取食水稻苗的草地贪夜蛾幼虫发育历期延长,卵孵化率、幼虫存活率、化蛹率和成虫羽化率均显著降低,雌性比率下降,雌成虫寿命显著缩短,单雌产卵量显著减少。取食玉米苗的草地贪夜蛾的种群增长趋势指数(I)为165.93,其在水稻上的相对适合度为0.21。【结论】相较于水稻,草地贪夜蛾在玉米上表现出更高的适合度,其偏好在玉米上取食和产卵。水稻不是目前侵入我国的草地贪夜蛾的嗜食寄主,但其可以通过取食水稻幼苗正常生长发育并完成生活史,在其种群密度较大、嗜食寄主植物缺乏时存在转移为害水稻的潜在风险。

Feeding and oviposition preference and fitness of the fall armyworm,Spodoptera frugiperda(Lepidoptera: Noctuidae), on rice and maize

【Aim】 This study aims to clarify the feeding and oviposition preference and fitness of the fall armyworm, Spodoptera frugiperda, on host plants rice and maize and then to analyze its damage risk to rice. 【Methods】 The feeding and oviposition preference of S. frugiperda were tested by free choice method. The development, survival rate and fecundity of S. frugiperda fed on maize and rice seedlings were investigated, and the fitness of S. frugiperda on rice was evaluated by the population growth trend index (I). 【Results】 There were significant differences in the feeding and oviposition preference of S. frugiperda to rice and maize. The choice rate of larvae to feed on maize increased with time during 2-48 h post infestation, while that on rice decreased with time. At 48 h post infestation, the choice rates of the 2nd and 4th instar larvae to feed on maize were 93.06% and 59.72%, respectively, which were 66.95 and 21.48 times as high as those to rice. In terms of oviposition preference, the number of eggs laid on maize was 8.64 times as high as that on rice after a free oviposition period of 6 d. The individuals of S. frugiperda fed on rice seedlings had longer developmental duration, lower egg hatching rate, larval growth rate, pupation rate, adult emergence rate and proportion of females, shorter female longevity and less eggs laid per female as compared to those fed on maize seedlings. The population growth trend index (I) of S. frugiperda fed on maize seedlings was 165.93, and the relative fitness of S. frugiperda on rice seedlings was 0.21. 【Conclusion】 S. frugiperda prefers to feed and lay eggs on maize rather than on rice, and shows a higher fitness on maize. Rice is a non.preferable host to S. frugiperda that has invaded China, but it can feed on rice seedlings to grow and develop normally and finish its life cycle. The results suggest that S. frugiperda may become a potential threat to rice production when it has a high population density and its preferable host plants are absent.