Utilization of Sargassum seaweed against Asian corn borer, Ostrinia furnacalis (Guenee) (Lepidoptera:Crambidae) for increased corn productivity

Anecdotal claims reveal that brown or Sargassum seaweed has long been used by farmers to reduce insect pest populations in cacao and various vegetables. A study was conducted at the National Crop Protection Center, College of Agriculture and Food Science, University of the Philippines Los Baños from 2015-2017 to validate farmer knowledge on reduced Asian corn borer populations when brown seaweed, Sargassum cinctum J. Agardh is placed on plot borders. Prominent volatile organic chemicals (VOCs) emitted by seaweed under sunlight and room conditions were identified by GCMS and differences in emission patterns were observed. In general, the fresh seaweed extract showed a higher percent repellency as compared to the dried seaweed extract. We identified for the first time the nature of the compounds emitted by S. cinctum and repelling the Asian corn borer. Some VOCs presented in combination did not produce synergistic effect. The behavioral responses of Asian corn borer (ACB) larvae and adult oviposition, effect on development, fecundity, hatchability of eggs and longevity to the brown seaweed, S. cinctum, was studied to elucidate the mechanism for reduced ACB populations in corn (Zea mays L.) with brown seaweed hanged on the plant as practiced by farmers. The methods included rearing pan and Petri plate bioassays to determine possible effects of volatile organic chemicals (VOCs) emitted by brown seaweed. Our results demonstrated that neonates and second instar larvae were apparently repelled by VOCs emitted by S. cinctum. VOCs did not affect significantly larval development, developmental periods, fecundity and longevity of adult male and female, O. furnacalis. Egg hatchability and larval survival were likewise not significantly affected by VOCs from the brown seaweed. The number of egg masses and number of eggs laid by female moths was reduced when brown seaweed was applied on corn under field cage conditions. Sargassum seaweed can be used together with other effective IPM strategies, especially in coastal areas, to reduce corn borer population. Brown seaweed can be an effective pest management strategy tool for low input and/or organic green corn production.