Repellency of marigold, Tagetes erecta L. (Asteraceae) volatile organic chemicals to eggplant fruit and shoot borer, Leucinodes orbonalis Guenee (Lepidoptera:Crambidae)
2015
Calumpang, S.M.F. | Ohsawa, K.
Insecticide use in eggplant is frequent due to the eggplant fruit and shoot borer (EFSB), Leucinodes orbonalis Guenee (Lepidoptera:Crambidae). Food safety, environmental and human health issues for applicators have been raised. There is a need to explore ecological approaches to reduce pesticide use. The authors tested the hypothesis that volatile organic chemicals from marigold flowers, Tagetes erecta L. (Asteraceae) disrupt host-finding behavior of EFSB. The methods include host-finding behavior assays in cages and Y-tube olfactometric bioassays to identify volatile chemicals in marigold flowers that repel EFSB. Behavioral bioassays were conducted at the National Crop Protection Center, College of Agriculture, University of the Philippines Los Baños from 2010 to 2011. Olfactometric bioassays using volatile organic chemicals of marigold flowers were conducted in 2013-2014. Fewer female adult landings were observed on the host plant, eggplant when marigold was present than eggplant alone, in laboratory cage bioassays over a 24 period. The percentage of damaged eggplants with marigold was significantly lower than sole eggplant. The average percent of shoot damage per eggplant with marigold was likewise significantly lower than sole eggplant. The repellency of volatile organic chemicals emitted by marigold flowers was likewise demonstrated with citral and 1- dodecene showing 64-68% repellency to female EFSB. A 10-flower equivalent displayed 72% repellency. Field trials need to be conducted to evaluate the appropriate cropping system that can effectively reduce EFSB populations.
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