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.