Efficacy of Neem (Azadirachtin indica) biopesticide against tomato leaf miner (Tuta absoluta) in greenhouse conditions

The Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most devastating invasive new pest affecting tomato crops in Kenya. This study evaluated the insecticidal effect of neem (Azadirachtin indica) against Tuta absoluta at various dose rates namely; 20 ml/20L, 40 ml/20L, 60 ml/20L and control where only water was sprayed in greenhouse conditions. Neem was compared to Coragen®, a synthetic chemical recommended for lepidopteran pests. The experiment was laid out in a complete randomized design with four replications. The results revealed that neem significantly (p < 0.05) lowered Tuta absoluta populations on treated plants compared to the untreated. The mean Tuta absoluta population reduction at 40ml/20L and 60 ml/20L was significantly (p < 0.05) higher than that at 20 ml/20L, the lowest dose rate. Mean population reduction at 40 ml/20L and 60 ml/20L dose rates did not differ. Corgen® treatment had the lowest Tuta absoluta population in the greenhouse compared to in other treatments. High fruit damage of over 90% was recorded in control treatments compared to 30.0%, 23.4% and 20.0% for 20 ml/20L, 40 ml/20L and 60 ml/20L dose rates, respectively. The results demonstrate the potential of neem in reducing Tuta absoluta population which can be exploited in the pest control mitigation program for sustainable management.