Phytochemicals for Pest Control that Restrain the Voracity of Spodoptera litura Larvae

農学 昆虫世界の謎解きThe common cutworm, Spodoptera litura (F.), is one of the most destructive polyphagous pests in the world. To identify phytochemicals that can restrain the voracity of S. litura larvae and thus be used for pest control, the larvae were fed leaves from unidentified Lavandula sp. (Lamiaceae), Japanese pepper (Rutaceae: Zanthoxylum piperitum), Japanese mustard spinach (Brassicaceae: Brassica rapa var. perviridis), narrowleaf angelonia (Scrophulariaceae: Angelonia salicariifolia), and soybean (Fabaceae: Glycine max var. Tamahomare). We observed that S. litura larval growth was clearly inhibited by Japanese mustard spinach and narrowleaf angelonia leaves. Larvae that were fed leaves from these two species weighed less than larvae that were fed soybean leaves. When we determined the amounts of mono-, di-, tri-, and tetrasaccharides in S. litura larvae that were fed either Japanese mustard spinach, narrowleaf angelonia, or soybean (Tamahomare) leaves, we found lower levels of these sugars in larvae that were fed leaves from the former two plant species.チョウ目幼虫であるハスモンヨトウは広い食性を持つ重要害虫の一種であり、世界中に分布する。幼虫は暴食するからこそ害虫になりうる。本研究では、暴食を抑える植物由来の化学成分発見を目指して、ラベンダーの未同定種（シソ科）・サンショウ（ミカン科）・コマツナ幼苗（アブラナ科）・アンゲロニア（オオバコ科）・ダイズ（タマホマレ）（マメ科）をハスモンヨトウに与え、その生育の様子を調べた。ハスモンヨトウ幼虫の生育はラベンダー未同定種・サンショウ・コマツナ若芽・アンゲロニアで確認した。このうち、ダイズと比較すると、サンショウ・アンゲロニアで有意に体重増加は阻害されていた。また、ハスモンヨトウ体内の単糖類から四糖類を分析したところ、サンショウ・アンゲロニアを与えたハスモンヨトウ血中の多糖類は有意に減少していた