Cabbage loopers, Trichoplusia ni, often cut a narrow trench across a leaf before feeding on the distal section. The trench reduces the larva's exposure to exudates, such as latex or resin, during feeding. Plant species that do not emit exudate, such as Plantago lanceolata, are not trenched. However, if exudate is applied to a looper's mouth during feeding on P. lanceolata, the larva will often stop and cut a trench. Dissolved chemicals can be similarly applied and tested for effectiveness at triggering trenching. With this assay, I have identified compounds in lettuce latex and parsley oil, plus some pesticides and medicinal drugs that elicit trenching. These results document that noxious plant compounds trigger trenching and suggest that the trenching assay can be used to identify plant compounds of potential use in agriculture or medicine.
Species 1: Lepidoptera Noctuidae Trichoplusia ni (cabbage looper)
Species 2: Asterales Asteraceae Lactuca sativa (lettuce)
Species 3: Apiales Apiaceae Petroselinum crispum (parsley)
Keywords: plant-herbivore interactions, latex
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA