Drop Size, Volume of Application and Use of Adjuvant in Deposition and Control of Yellow Spot (Pyrenophora tritici-repentis) in Wheat

Abstract

We evaluated the effect of droplet size, volume of application and use of adjuvant in the efficiency of a triazole fungicide strobilurin mixture, to control yellow spot on wheat, caused by Pyrenophora tritici-repentis. The experiment was conducted in a commercial farm hinterland Experimental Station Mario A. Cassinoni (School of Agriculture, University of the Republic), in Paysandú, Uruguay. The design was a randomized block with 2x2x2 factorial arrangement of treatments, with the factors of variation droplet size, spray volume, and adjuvant use, plus a control without fungicide. The distribution in different plant strata was evaluated by fluorometry techniques using fluorescent tracer Blankophor ® 267 % BA. The variables evaluated were the deposition on wheat leaves through the estimation of tracer deposition, impacts density, efficiency of disease control, and grain yield. The results indicated that the use of 158 l.ha-1 and the presence of adjuvant, determined higher deposition of the tracer with extremely large drops, followed by the use of midsize drops. However these differences had no effect on the variables that estimated the effects on disease control and grain yield. Only a tendency was determined to a better control of the disease with the use of midsize drops, perhaps in response to the increased coverage.