草地螟对寄主植物的选择性及其化学生态机制

Oviposition preference of the meadow moth, Loxostege sticticalis L., on different host plants and its chemical mechanism

田间自然条件下,草地螟成虫产卵对不同植物具有明显的选择性,其中灰菜上落卵量最多,占调查总卵量的50%以上;甜菜、大豆上次之,玉米和马铃薯上最少。在室内条件下,草地螟成虫产卵对灰菜、大豆、玉米和马铃薯的选择性与田间调查结果完全吻合。而且,草地螟幼虫的嗜食性与成虫产卵对寄主的选择性是一致的。吸附、收集上述植物的挥发物后进行GC-MS测定,并利用风洞进行了生测。其中灰菜和大豆的主要挥发物成分为反-2-己烯醛、青叶醇、青叶酯、1-十八烯等;玉米和马铃薯的挥发物性成分包括青叶酯、芳樟醇、香叶醇、紫罗酮、1-十八烯。生测结果表明,灰菜的挥发物对草地螟雌蛾引诱力最大,选择系数为78%;大豆苗挥发物对其也有较高的诱虫活性;但玉米和马铃薯几乎无引诱作用。自然生长的4种植物的诱虫结果与其挥发物的诱虫结果相似。这些生测结果与成虫和幼虫选择寄主的一致性反映了草地螟选择寄主行为的化学机制。

The meadow moth, Loxostege sticticalis L. （Lepidoptera： Pyralidae ） is an important polyphagous pest in the northern China. The oviposition preference of L. sticticalis on different host plants and its chemical basis were studied in the field and laboratory. Different wild host species were identified in fields of soybean, sugar beet, corn and potato in Hebei province, and the number of eggs laid on each plant species was counted. More than 50% of the eggs counted on all host plants were found on the common weed lambsquarters, Chenopodium album L. （Chenopodiaeeae）. Significantly fewer eggs were found on soybean and sugar beet, and only a few eggs were found on corn and potato. Choice-tests in the laboratory were conducted with both adults and larvae using three crop species （soybean, corn and potato） with or without the weed lambsquarters. Results from the laboratory were consistent with that from the field, with the highest proportion of eggs laid on lambsquarters （〉50%） compared to soybean, corn or potato. Third, fourth and fifth instar larvae preferred to feed on soybean foliage compared to potato or corn~ however, larvae fed only on lambsquarters when it was added into a cage with the three crop species. The oviposition preference on different host plants by L. sticticalis adults was positively correlated with the feeding preference by the larvae. Headspace volatiles of lambsquarters and soybean collected on Tenax were attractive to L. sticticalis females in wind tunnel tests, with preference indices for each species 78% and 38%, respectively. However, volatiles from corn and potato plants did not act as attractants. The chemical compositions of the volatiles collected from different host plants were analyzed using GC-MS. Relatively large amounts of E-2-hexenal and Z-3-hexen-1-ol were found in the volatilesfrom the preferred hosts lambsquarters and soybean, while the same compounds were found in much smaller quantities in corn and potato. Linalool, E-3,7-dimethyl-2,6-octadien-1-ol and β-ionone were identified in the headspace volatiles of corn and potato plants but not lambsquarters or soybean plants. These results suggest that volatiles may play an important role in the oviposition preference of L. sticticalis, and possibly in the feeding preference of larvae as well.