Investigation of Insecticidal Activity of Blend of Essential Oil of <i>Cymbopogon schoenanthus</i> and neem oil on <i>Plutella xylostella</i> (Lepidoptera: Plutellidae)

Abstract

Plant and plant derived materials appear nowadays as a safe alternative to conventional pesticides to fight against crop pests. For this purpose, activity of blend (1:1 weight/weight) of Cymbopogon schoenanthus essential oil and neem (Azadirachta indica) seed oil on diamondback moth (Plutella xylostella) through contact and feeding methods were investigated and compared to each individual botanical. In the contact method, the combination of Cymbopogon schoenanthus/Azadirachta indica (LC50 = 23.3 mg/ml) oils exhibited medium activity showing higher toxicity than neem oil (58.39 mg/ml) and lower toxicity than Cymbopogon schcoenanthus essential oil (LC50 = 12.08 mg/ml). In feeding method, the toxicity resulted from the blend of Cymbopogon schoenanthus/Azadirachta indica (LC50 = 47.02) was slightly higher than both considered separately (LC50 = 52.39 and 53.63 for Cymbopogon schcoenanthus and neem respectively). Neem oil and the blend of Cymbopogon schoenanthus /neem exhibit strong antifeedance effect and inhibition of adult emergence of Plutella xylostella. The interaction between the mixture of Cymbopogon schoenanthus/ neem was additive resulting in increasing of insecticidal spectrum and could be used as an alternative to chemical pesticide in cabbage protection against Plutella xylostella.