author(s)
Eman H Ismail

abstract
The present investigation was conducted to determine the toxicity, repellency and latent effects of seven medicinal plant oils against the confused flour beetle, Tribolium confusum and the red flour beetle, T. castaneum (Coleoptera: Tenebrionidae). The tested oils were camphor (Eucalyptus globulus), guava (Psidium guajava), ginger (Zingiber officinale), turmeric (Curcuma longa), nigella (Nigella sativa), star anise (Illicium verum) and thyme (Thymus vulgaris). Results revealed that the most effective oils against T. confusum were turmeric, ginger, star anise, thyme and camphor which induced mortality percentages of 90.0, 70.3, 37.5, 36.4 and 35.0, respectively with the highest concentration (5ml oil/100g flour). Turmeric oil showed highly significant reduction in number of alive beetles after treatment at different concentrations and exposure times. In repellency tests, turmeric oil produced complete repellency (100%) in both multiple- and two-choice in food-preference bioassays. Moreover, it produced repellency class of V (96.67% repellency) in area-preference bioassay. Similarly, turmeric oil showed highly significant protection against the confused flour beetles’ infestation up to six months (with mortality percentages ranging from 99.3% after 15 days to 96% after 180 days after oil application). But regarding T. castaneum, the most effective oils were ginger, turmeric, thyme, nigella and guava at mortality percentages of 75.8, 63.5, 34.7, 32.8 and 26.6, respectively with the highest concentration. Ginger oil was the most effective in reducing beetles’ numbers in toxicity tests. Also, it showed highly significant repellent effects in both multiple- and two-choice tests and ranked Class V (94.17% repellency) in area-preference tests. The latent effect tests showed that ginger was the most effective oil in protecting flour from the red flour beetles’ infestation. The mortality percentage was 77.7% after 15 days till 63.7% mortality after 180 days of oil application.