"Peanut (Arachis hypogaea) Response to Fungicides and Herbicides Applied using Different Spray Nozzles"

Abstract

Late leaf spot [caused by Nothopassalora personata (Berk. & M.A. Curtis) U. Braun, C. Nakash, Videira & Crous] is an economically important disease in peanut (Arachis hypogaea L.) and fungicides are used routinely to protect peanut from infection and the resulting yield loss. Herbicides are an important component of effective weed management in peanut. Concern over particle drift of pesticides exists in the farming community, especially after stewardship issues associated with synthetic auxin application in herbicide resistant crops in the United States. Spray nozzles that deliver larger droplets that are less prone to drift is a possible solution to this issue. However, fungicides may be less effective in penetrating the crop canopy and covering foliage for protection from pathogens with these nozzles compared with nozzles delivering smaller droplets. Research was conducted to compare suppression of late leaf spot disease when chlorothalonil, prothioconazole plus tebuconazole, azoxystrobin, pyraclostrobin, and chlorothalonil were applied sequentially every 14 days using hollow cone nozzles (fine droplet size), regular flat fan nozzles (medium droplet size), air induction flat fan nozzles (coarse droplet size), and turbo teejet induction nozzles (ultra-coarse droplet size). Regular flat fan and hollow cone nozzles were slightly more effective in delivering fungicides based on canopy defoliation at harvest compared with turbo teejet induction nozzles and in some cases air induction nozzles. However, suppression of pathogens by fungicides applied using all four nozzle types prevented canopy defoliation adequately to protect peanut from yield loss. In a separate experiment, peanut yield and control of common ragweed (Ambrosia artemisiifolia L.) and late leaf spot did not differ at harvest when herbicides and fungicides were applied with air induction or turbo teejet induction nozzles throughout the cropping cycle. These results indicate that farmers can apply fungicides and herbicides to peanut using nozzles that limit potential for particle drift with minimal concern over reduced pesticide efficacy and protection of yield from pests.