Indirect Effect of Some Insecticides on Tomato Early Blight (Alternaria solani) Under Laboratory and Greenhouse Conditions

Matrood, A.A.A., A. Rhouma and A.H.F. Al-Taie. 2022. Indirect Effect of Some Insecticides on Tomato Early Blight (Alternaria solani) Under Laboratory and Greenhouse Conditions. Arab Journal of Plant Protection, 40(3): 231-239. https://doi.org/10.22268/AJPP-40.3.231239 Early blight disease is one of the serious diseases of tomato caused by Alternaria solani. In some instances, annual economic yield loss due to this disease was estimated at 80%. Currently, pesticide applications are used for the management of early blight disease due to the lack of resistant cultivars. The effect of treatment of the susceptible tomato cultivar Super Marmond with three insecticides (Diazinon, Match® 050 EC and Vertimec®) was evaluated under laboratory and greenhouse conditions. In vitro assay showed that the pesticide Vertimec® (at a concentration of 300 ppm) was the most effective against A. solani with mycelial growth inhibition above 93%, inhibition of fungal sporulation to 0.26x103 spores/ml, and spore germination inhibition of 98.79%. In addition, there was a reduction in A. solani spores and their dry weight (0.0144 mg) in the presence of Vertimec®. In greenhouse experiments, when Vertimec® was used curatively on tomato leaves against A. solani, it lowered significantly disease severity (20.33%). The effect of this insecticide was not limited only to the protection of tomato plants but it also improved their growth by increasing the tomato shoot fresh and dry weights (21.94 g and 3.85 g, respectively) as well as the root fresh and dry weight (3.84 g and 0.89 g, respectively). Based on the results obtained, it can be concluded that Vertimec® could be used for early blight management when the tomato crop is also infested with insect pests. Keywords: Alternaria solani, early blight, insecticide, tomato.