Chemical composition and fumigant toxicity of the essential oil from Tithonia diversifolia (Hemsl.) A. Grey against two major stored grain insect pests.

The essential oil (EO) from the leaves of Tithonia diversifolia (Hemsl.) A. Grey was investigated to determine chemical composition and fumigant toxicity against two major stored grain pests rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and red flour beetle, Tribolium castaneum (Herbst.) (Coleoptera: Tenebrionidae). A total of 78 compounds were identified by GC-MS of which α-Pinene (63.62%), Bicyclo [3.1.0] hexane, 4-methylene-1-(1-methyl ethyl)- (14.68%) and 1,6,10-Dodecatrien-3-ol, 3,7,11-trimethyl-, (E)- (2.34%) were most abundant. EO from leaves of T. diversifolia showed strong fumigant activity against S. oryzae adults with LC50 values of 95.12, 77.00 and 74.68 µL/L air after 24, 48 and 72 h of exposure whereas for T. castaneum the LC50 values were 102.67, 98.12 and 81.54 µL/L air, respectively. Mortality rates increased with increasing exposure periods and increasing concentration. These naturally occurring materials derived from EO of T. diversifolia could be used to manage the populations of S. oryzae and T. castaneum. It was found that the EO's of T. diversifolia is very effective as a fumigant against stored grain insect pests and can also be used as an alternative to the synthetic fumigants. [ABSTRACT FROM AUTHOR]