Effect of Trichilia americana extract on feeding behavior of Asian armyworm, Spodoptera litura

We investigated the desensitization of Asian armyworms, Spodoptera litura, to a crude methanolic extract of wood Trichilia americana. Following repeat ed exposures to the extract over four days, desensitization was observed un der no-choice conditions at low extract concentration (0.5 mug/cm(2)). No d esensitization was observed under choice conditions or at a higher concentr ation (5.0 mug/cm(2)). Repeated exposures of larvae to the extract over 7.5 hr showed that larvae increasingly tolerated the extract due to hunger, ra ther than showing true desensitization. When larvae were exposed to the ext ract in test arenas of different sizes, larvae showed reduced feeding and d esensitization as arena size increased. Finally, treatment of whole cabbage plants with extract resulted in larvae abandoning the plant. The crude ext ract was effective at protecting the plants. although desensitization did n ot occur. because the larvae moved away from the plant.