Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2011
Publication Date: 11/4/2011
Citation: Dowd, P.F., Johnson, E.T., Vermillion, K., Berhow, M.A. 2011. Coconut leaf bioactivity toward generalist maize insect pests. Entomologia Experimentalis et Applicata. 141:208-215. Interpretive Summary: Insects that damage corn cause billions of dollars in losses each year due to lower yields and contamination with mold toxins. New sources of broad, stable resistance to these insect pests would help reduce these losses. Tropical plants are often better defended against insects than temperate ones, and could be a good source of resistance. Tropical palm leaves were found to have high resistance to two corn ear feeding caterpillars. Active components could be extracted and separated. Introduction of comparable corn genes responsible for biosynthesis of the active components from the palm into corn through breeding or genetic engineering should result in plants that are less heavily damaged and contaminated by mold toxins, resulting in healthier corn for humans and animals and corn that is more acceptable to importers.
Technical Abstract: Tropical plants are often more resistant to insects than temperate plants due to evolution of robust defenses to cope with a more constant insect threat. Coconut (Cocos nucifera L.) has very few chewing leaf feeding insect pests and was tested against two omnivorous leaf feeding caterpillar species, the corn earworm Helicoverpa zea and fall armyworm Spodoptera frugiperda. Feeding on leaf tissues from the most recently expanded leaves of a coconut variety caused significant mortality of S. frugiperda and significant reduction in growth rates (as indicated by survivor weights) of both S. frugiperda and H. zea. Responsible factors did not appear to include proteins or other polymers. Components responsible for activity were acetone extractable and separable by thin layer chromatography. Multiple separated components caused significant reductions in growth rates of both insect species. The most active component caused browning of test diets, suggesting it contains a compound capable of oxidation, which is also a likely mode of action.