بررسی اثر قارچ‌کش های مختلف بر شدت بیماری برق زدگی نخود

Ascochyta blight caused by Didymella rabiei is one of the most important disease of chickpea in the world that affects the quality and quantity of this crop. Different strategies such as seed disinfection, sanitation, and crop rotation have been used to reduce the damage. The use of resistant cultivars is the most useful and effective management strategy to minimize yield losses due to the Ascochyta blight but, a high level of resistance have not been bred into cultivars, due to lack of germplasm exhibiting a high degree of resistance and under favour environmental conditions for disease selection and application of fungicides is essential. The objective of this study was to evaluate the efficacy of some fungicides on disease severity of ascochyta blight. First, inhibitory effect of fungicides (captan, carbendazim, tridemorph, chlorothalonil) in 0.01 to 100 ppm concentrations on growth of fungus mycelium was evaluated in vitro. Under field conditions during 2017 year, effect of fungicides was evaluated on disease severity at concentrations recommended by the protocol of manufacturer. A field experiment was conducted in a randomized complete block design with three replications. The Greet, a local accession with kabuli seed type and susceptible to ascochyta blight used in this study. Inoculation of plants was carried out at the 5th leaf and flowering stage using infected plant debris and spore suspension of fungus in early morning and late evening. Fungicides were sprayed at flowering stage two times. Disease severity and score of plants were rated on the basis of a rating scale (1-9, 1: no symptom and 9: death of 100% plant). In vitro results showed that maximum and minimum inhibitoy radial growth of mycelium was at dilution of 100 and 0.01 ppm of tridemorph and chlorothalonil fungicides respectively. Although analysis of field data showed that effect of fungicide was not significant on disease severity at statistical level of 5%, but in comparison efficacy of fungicides, chlorothalonil showed better efficacy in reducing of disease score and severity. Moreover evaluation of weather data such as temperature, precipitation and relative humidity during of this study showed that due to favorable environmental conditions for the growth and development of disease agent, application two times of fungicides spray were not sufficient to significantly reduce disease score and severity.