Evaluation of Different Phytochemical Extracts for the Management of Early Blight of Tomato

Abstract

Background: Early blight is a serious disease of tomato that reduces both yield and quality. Farmers often use chemical sprays to control it, but these can harm the environment and lose effectiveness over time. Using plant-based extracts is a natural and safer option to manage this problem. Objective: To evaluate the various phytochemical extracts for the management of early blight of tomato. Methdology: The antifungal efficacy of ten medicinal plants, namely; prickly acacia (Acacia nilotica L.), datura (Datura alba L.), black pepper (Piper nigrum L.), turmeric (Curcuma longa L.), garlic (Allium sativum L.), ginger (Zingiber officinale L.), oleander (Nerium oleander L.), eucalyptus (Eucalyptus globulus L.), ashwagandha (Withania somnifera L.),  chinese date (Ziziphus mauritiana L.) along with the fungicide Mancozeb, were evaluated against Alternaria solani, the causal agent of tomato early blight, under in vitro and screen house conditions, and data was analyzed using the CRD model (ANOVA). Results: The In-vitro experiment with Potato Dextrose Agar (PDA) medium amended with 500 mg/L dose of the plant powder preparations, Mancozeb to be the most effective in reducing colony diameter of A. solani after 7-14 days of incubation. All the ten tested plants also reduced the colony diameter of A. solani significantly (p<0.05) as compared with unamended control. However, garlic, oleander and turmeric were found to be superior to the other plants. Similarly, these three plants, along with Mancozeb, also markedly reduced fungal biomass and spore concentration. In the screen house study (3000 mg/L), disease severity after the second application was lowest in Mancozeb-treated plants (16.7%), followed by garlic (26.6%), oleander (26.7%), and turmeric (30.0%), while the untreated control showed the highest severity (96.7%). Yield assessment revealed that during the first picking, maximum fruits per plant were obtained with Mancozeb (6.3), followed by garlic (5.3), oleander (4.7), and turmeric (4.7), whereas untreated, eucalyptus, and datura-treated plants produced the lowest (3.0 fruits each); a similar trend was recorded during the second picking. Furthermore, Mancozeb, garlic, oleander, and turmeric significantly improved plant growth attributes, including plant height, fresh weight, and dry weight, compared to untreated plants. Conclusions: It is concluded that garlic, oleander, and turmeric can be used as effective alternatives for managing early blight in tomato, with oleander being particularly promising due to its low cost and abundant availability.