Investigation on the effects of Chlorothalonil for control of tomato Early blight disease.

Early blight (target spot), caused by the fungus Alternaria solani, which survives in infected leaf or stem tissues on or in the soil, is one of the most common diseases of tomato. In spite of its name, the disease may occur at any time during the growing season. The fungus attacks leaves, stems and fruit. It can also cause disease on potato, pepper, and eggplant. This disease causes direct losses by the infection of fruits and indirect losses by reducing plant vigor. As the disease progresses, leaves turn yellow, wither, and drop from plants. Tomato plants severely infected by Early blight produce low yields of undersized fruit. Generally, fruit are also show signs of sun-scald since leaves aren't present to protect fruit from direct sunlight. Although this disease usually affects older, senescing plants, it can cause complete defoliation when environmental conditions are optimal for disease development. Early blight control is based on crop rotation, removal and destruction of crop debris from previous crops, staking, mulching, and using of fungicides. In this study efficacy of Cholorotalonil (Daconil SC 725) at three different doses (2, 2.5, 3 l/h), Equation Pro %52.5 WG at three different doses (350, 400, 450 g/h), Daconil WP 75% at one dose (2 kg/h) and chek was evaluated to control Early blight of tomato (Alternaria solani) in two years. The trial was laid down as full randomized design with 8 treatments and four replications. Foliar applications of fungicides were made at 5, 7, 10 and 14 day intervals and started after early symptoms seen. The results are expressed as the percentage of leaf area of marked plants infected by Alternaria solani. Disease severity on leaves was classified from 1 to 7 before each spray and mean of disease severity was calculated using the Horsfall and Barrat scale for each marked plants (Horsfall, J. G., and R.W. Barrat, 1945). Area under disease progress curve (AUDPC) for each plot is calculated by plotting mean disease severity of the five evaluations in order to compare treatments. The data of separate sampling and AUDPC were analyzed by SAS soft ware. The analyses of variance results revealed that there are significant differences between different treatments at P0.05 and P0.01 in all sampling and AUDPC for both years. Also Duncan's Multiple Range Test tables for AUDPC in both two years showed that Cholorotalonil (Daconil SC 725) 3 and 3.5 l/h, and Equation Pro %52.5 WG (400, 450 g/h) are the best treatments to control of Tomato Early blight disease, so the use of Cholorotalonil (Daconil SC 725) 3 l/h and Equation Pro %52.5 WG 400 g/h recomded with 7-10 days interwal