In vitro and greenhouse evaluation of botanical extracts for antifungal activity against Phythopthora infestans

The aim of this study was to evaluate plant extracts for antifungal activities against Phythopthora infestans (Mont.) de Bary, an important pathogen of potato which causes late blight disease. Acetone, ethyl acetate and water extracts of garlic (Allium sativum L.), Pawpaw (Carica papaya), Neem (Azadirachta indica), Mexican marigold (Tagetes minuta) and peri –winkle (Vinca rosea) were screened in vitro for their antifungal activities against Phythopthora infestans using the disc agar infusion and microtitre double-dilution techniques. The same extracts were then tested for antifungal activity in vivo in the greenhouse on inoculated potato plants. The water extracts of Allium sativum and Azadirachta indica were active against Phythopthora infestans and had a minimum inhibitory concentration (MICs) of 1.65 mg/ml. MICs of Allium sativum, Azadirachta indica and Tagetes minuta acetone extracts were 0.78, 3.13 and 6.5 mg/ml respectively against Phytophthora infestans. Allium sativum and Azadirachta indica water and acetone extracts performed well and they effectively reduced potato late blight in the greenhouse. These extracts compared well with the reductions due to application of Ridomil, a synthetic fungicide applied at 42.5g/l (active ingredient) and also with levels in the non-inoculated control. Allium sativum and Azadirachta indica were effective both in vitro and in vivo in controlling late blight have a potential to be used as fungicides against the disease. The plants are readily available and the extraction method is also simple and could lead to high adoption as fungicides by resource poor farmers. MS History: 20.09.2014 (Received)-09.10.2014 (Revised)-20.10.2014 (Accepted) Citation: Ngadze, E. 2014. In vitro and greenhouse evaluation of botanical extracts for antifungal activity against Phythopthora infestans. Journal of Biopesticides, 7(2):198-203.