The efficacy of some medicinal plant extracts and essential oils against potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae)

The potato tuber moth (PTM), Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae), is an important pest of potato and other solanaceous plants. It is cosmopolite and oligophage that exist in most countries where potatoes are grown. Because of chemical treatment adverse effects, there is a necessity to find safe alternatives to synthetic insecticides. So, medicinal plants are promising since they are safe, inexpensive and effective. In this direction, potato tubers were dipped in 1 ml of 5% methanolic extracts of fumitory, licorice, lavender and oregano. The percentage of first larval penetration to tubers and oviposition-preference of mentioned medicinal plants was investigated on PTM. Subsequently, fumigant toxicity of essential oils of basil, european pennyroyal, lavender, mint and savory were investigated on P. operculella. Treated potato tubers by methanolic extract of lavender elicited the lowest percentage (19.3) of first larval penetration. Studying of oviposition-preference demonstrated that the most number of eggs were laid on control and fumitory with 28 and 10 eggs after three days, respectively. Probit analysis of essential oils showed that the most effective oil was savory which exhibited LC50 value on adults of PTM equivalent to 0.048 µL/L air.