Fumigant Activity of Tridax procumbens (Asterales: Asteraceae) Essential Oil Against Sitophilus zeamais (Coleoptera: Curculionidae) and Its Effects on Thai Rice Seed Germination

Fumigant activity of the essential oil extracted from Tridax procumbens L. (Asterales: Asteraceae) by water distillation was assessed against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), together with its effect on the germination of three Thai varieties of rice, Oryza sativa L. (Poales: Poaceae). Tridax procumbens essential oil contains 25 compounds with five principal components as 1,2-cyclooctanediol (11.49%), hexanal (5.34%), 4-heptenal (4.92%), 2,4-nonadienal (3.10%), and 1,6-dimethylhepta-1,3,5-triene (1.67%). Tridax procumbens essential oil was a fumigant toxin to S. zeamais adults with a median lethal concentration (LC50) of 1,509.79 ll/L air 24 h after exposure. The highest concentration of 250 ll/L air of T. procumbens essential oil showed low efficacy in killing adults of S. zeamais at 24 h with 10% mortality. This concentration also affected newly emerged progeny (F1) of S. zeamais compared to the control, with the highest reduction of 92.87%, and also decreased seed germination of the three varieties of Thai rice RD6, Kham Na Sinuan, and KDML at 94.25, 96.0, and 93.25%, respectively, compared with the control (98.0- 98.75%). Results indicate that essential oil from T. procumbens has potential for application on stored products to control progeny of S. zeamais that cause seed damage.