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Chemical Control of Foliar Diseases of Peanuts, Peppers, and Onions as Affected by Spray Nozzle Types, Nozzle Orientations, Spray Intervals, and Adjuvants. T. A. Kucharek, Professor, Plant Pathology Department, University of Florida, Gainesville 32611. R. E. Cullen, Plant Pathologist, and R. E. Stall, Professor, Plant Pathology Department, University of Florida, Gainesville 32611, and B. Llewellyn, Extension Agent, 4320 S. Orlando Dr., Sanford, FL 32771. Plant Dis. 70:583-586. Accepted for publication 27 December 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-583.

The efficacy of disease-control chemicals applied at low spray pressure (2.1 kg/cm2) was the same if sprayed through hollow-cone or flat-fan nozzles for control of peanut leaf spot, bacterial spot of pepper, and blast or purple blotch of onions, four diseases that represent different pathogen and crop canopy types. Control of bacterial spot of pepper was best when maneb plus zinc sulfate was added to a copper hydroxide spray that was applied twice rather than once each week. Control of blast and purple blotch on onions was best when a spreader-sticker was added to the mancozeb spray, which was applied through two nozzles over the center of each row with one oriented forward (45) and the other backward (45). When nozzle numbers per row were reduced from three to one for pepper but the sprays were directed primarily to the young, upper leaves, which are most susceptible to bacterial spot, disease control was not strongly compromised. When nozzle numbers were reduced from three to one for peanut and the sprays were directed to the center of row-canopy exclusively, peanut leaf spot control was improved slightly in that zone. A slight increase in peanut leaf spot occurred in the row-middle zone (vine growth between row centers) that received no sprays, but yield was not compromised. In contrast, when nozzle numbers per row were reduced from two to one (oriented downward) and no adjuvant was added to the spray mix, control of onion blast and purple blotch was inferior to that obtained with treatments where two nozzles per row were used in conjunction with the adjuvant.

Keyword(s): Allium cepa, Alternaria porri, Arachis hypogaea, Botrytis sp., Capsicum annuum, Cercospora arachidicola, Cercosporidium personatum, Xanthomonas campestris pv. vesicatoria.