Comparison of Five Fungicides on Development of Root, Crown, and Fruit Rot of Chile Pepper and Recovery of Phytophthora capsici from Soil.

Abstract

The activity of five fungicides, azoxystrobin, dimethomorph, fluazinam, fosetyl-Al, and metalaxyl (subsequently replaced with mefenoxam by the manufacturer), was compared for effects on the development of root, crown, and fruit rot of chile pepper and on recovery of Phytophthora capsici from naturally infested soil. When inoculated with zoospores, plants survived longer and shoot and root fresh weights were greater for plants drenched with metalaxyl at 10 μg/ml than for plants treated with the same rate of azoxystrobin or dimethomorph. At 100 μg/ml, the duration of plant survival was greater for dimethomorph and fluazinam than for azoxystrobin; however, shoot and root growth did not differ. In soil naturally infested with P. capsici, survival and growth of shoots and roots for plants treated with dimethomorph at 100 μg/ml were greater than for those treated with the same rate of azoxystrobin or fluazinam. The most effective compounds for inhibition of lesion development on stems and fruit were mefenoxam at 1,200 μg/ml and dimethomorph at 480 μg/ml. Recovery of P. capsici from soil treated with each of the five tested compounds was significantly less than that recorded for soil not receiving a fungicide. The potential and relative value of azoxystrobin, dimethomorph, fosetyl-Al, and fluazinam as chemical management tools for Phytophthora blight on chile pepper, in addition to metalaxyl (replaced with mefenoxam), has been demonstrated.