Contact and fumigant toxicity of plant essential oils and efficacy of spray formulations containing the oils against B‐ and Q‐biotypes of Bemisia tabaci

Abstract

The contact + fumigant toxicity of 92 plant essential oils and control efficacy of 18 experimental spray formulations containing nine selected essential oils (0.5 and 0.1% sprays) and six commercial insecticides to females from B- and Q-biotypes of Bemisia tabaci were evaluated using vapour-phase mortality and spray bioassays. Garlic and oregano (LC50 , 0.15 mL cm(-3) ) were the most toxic oils against B- and Q-biotype females. Strong fumigant toxicity to both biotype females was also obtained from catnip, cinnamon bark, clove bud, clove leaf, davana, savory and vetiver Haiti oils (LC50 , 0.17-0.48 mL cm(-3) ). The 0.5% sprays of these oils (except for thyme red oil) resulted in 90-100% mortality against both biotype females. Only garlic applied as 0.1% spray provided 100% mortality. Spinosad 100 g L(-1) suspension concentrate (SC) treatment resulted in 92 and 95% mortality against both biotype females, whereas acetamiprid 80 g L(-1) wettable powder (WP), imidacloprid 80 g L(-1) SC, thiamethoxam 100 g L(-1) water-dispersible granule (WDG) and pyridaben 200 g L(-1) WP treatments resulted in 89-100% mortality against B-biotype females only. In the light of global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment, the essential oils described, particularly garlic, cinnamon bark and vetiver Haiti, merit further study as potential insecticides for the control of B. tabaci populations as fumigants with contact action.