Evaluation of Fungicides and Botanical Extracts for the Management of Tomato Late Blight Caused by Phytophthora infestans

Abstract

Phytophthora infestans (Mont.) de Bary causes one of the most devastating diseases of tomato (Solanum lycopersicum L.) and can cause severe losses in yield and economy worldwide (late blight). Rapid growth and several infection cycles occur in a single growing season under favorable environmental conditions (cool temperatures and high humidity). Traditional control practices are mainly depending on the synthetic fungicides, because the pathogen has aggressive and polycyclic nature which leads to the high need for control measures. Contact fungicides like mancozeb and chlorothalonil as well as systemic fungicides like phenylamides, carboxylic acid amides and newer chemistries like oxathiapiprolin have proved to be very effective in reducing disease severity and protection yield. Despite its success, however, there is a high level of fungicide dependence, which has led to increased production expenses, contamination of the environment and the establishment of widespread fungicide-resistant populations of P. infestans. To address these challenges, research has been oriented towards the development of botanical extracts as more environmentally-friendly alternatives or supplements to chemical fungicides. Synthetic compounds obtained from plants like Moringa oleifera, Lantana camara, Eucalyptus spp., and Carica papaya have demonstrated promising antifungal effects on P. infestans through various mechanisms, including the inhibition of sporangial germination, the suppression of mycelial growth, and the activation of host defense mechanisms. While there is some variability in efficacy and formulation and in field performance, botanical extracts can provide benefits for decreasing the need for chemical inputs and delaying fungicide resistance. This review critically synthesizes the current knowledge on the role, efficacy and limitations of fungicides and botanical extracts for tomato late blight management. Mechanisms of action, resistance problems and incorporation of chemical and botanical methods into sustainable disease management are emphasized. Long-term, sustainable control of tomato late blight requires the use of integrated approaches that involve fungicides, botanicals, resistant cultivars and cultural methods.