Integrative effect of some synthetic fungicides with some biological agents in control of Rhizoctonia solani on cotton seedlings

Rhizoctonia solani is an important soil-borne pathogen which has a broad host range and cause damping-off or rottenness in root and crown of cultivated plants. The combined use of different control methods in IPM programs is an effective strategy against pathogens and is useful especially in resistance management programs. In this study, EC50 and EC25 values of three conventional chemical fungicides Zineb, Captan and Carboxin thiram and two biocontrol antagonist Pseudomonas fluorescens 73 and Trichoderma harzianum T22 were tested against R. solani in vitro and greenhouse condition. The results revealed that Carboxin thiram was effective than other fungicides with EC50 values of 0.05 ppm in vitro. The best control (75%) were obtained in combined use of Carboxin thiram fungicides with EC50 value of T. harzianum T22. and EC50 and EC25 values of P. fluorescens 73 in combination with Captan fungicide showed the best control (near 75%) in vitro. In green house tests that the control agents individually and in combination with each other were evaluated showed that, the best control of the disease were observed in positive control (without infection) and EC50 values of fungicides in combination with each of biocontrol agents. Overall results of this research showed that combined use of two antagonists with selected fungicides in both in-vitro and green house condition are effective than individual use of each control agent and may be it is possible to control the R. solani derived disease using this integrated method in cotton crop.