Use of non-chemical methods for the management of southern blight disease of carrot incited by Sclerotium rolfsii

Abstract

This experiment was conducted to assess the effect of Trichoderma harzianum, soil solarization, and biofumigant on southern blight dis-ease of carrot incited by Sclerotium rolfsii isolate CS 5. A series of in-vitro and in-vivo trials laid out to select a virulent isolate of S. rolfsii against the carrot variety New Kuroda and evaluated the mustard, cabbage, cauliflower, and broccoli leaf extracts for choosing an effec-tive biofumigant against test pathogen. Mustard was the most effec-tive in inhibiting the radial growth, and sclerotia formation (80.37 and 83.37%) of S. rolfsii (isolate CS 5) at 40% level of concentration followed by cabbage leaf extract (62.22 and 68.69%). On the contrary, a total of 10 isolates of T. harzianum were screened against the test pathogen on Potato Dextrose Agar (PDA) medium for choosing a dominant isolate of T. harzianum. The isolate Th-6 was found as the most active in inhibiting the radial growth (84.44%) of S. rolfsii fol-lowed by Th-1 (75.56%). In the application of T. harzianum, biofumi-gation, and soil solarization, the treatment appeared to be the most superior in reducing pre- and post-emergence mortality of carrot during secondary field trials. The lowest southern blight disease inci-dence (10.77%), and disease severity (12.78%) were found at the same treatment. Subsequently, the yield of carrot was increased 155.18% which might be due to the reduction of carrot disease as well as the addition of organic materials in the soil.