Controle químico da mancha branca do milho

Abstract

The white spot, though old in Brazil, occurred more frequently at the end of the cycle of corn plants when they are presented close to senescence. However, the disease began to be observed in younger plants, and can take early susceptible genotypes, with a consequent reduction in productivity, when coupled with environmental conditions favorable to the pathogen. The objective of this study was to evaluate the severity of maize white spot before the application of pesticides in two application periods (V8 or pre-flowering) to obtain the best strategy of chemical control in the management of this disease. The study was conducted at the experimental site of the Department of Agriculture, Federal University of Lavras, with simple hybrid super early AG9010, which is susceptible to disease. The experimental design was randomized blocks (DBC) with nine treatments and four replications, totaling 36 experimental plots. The treatments were: oxytetracycline + streptomycin (400, 500 and 600 g.p.c/ha), oxytetracycline (300, 400 and 500 g.p.c./ha), epoxiconazole + pyraclostrobin (750 ml.p.c/ha) and mancozeb (2500 g.p.c/ha). We evaluated the severity of the disease every seven days, a week after the application of treatments pre-flowering, 10 plants at random from each plot useful, determining the average severity. Data obtained on the severity of the disease in all ages were used to estimate the disease progress curve and area under the disease progress curve (AUDPC). Harvest was done manually, where the plots were harvested only useful (two central lines of four meters of each plot). The productivity of the treatments was adjusted to 12% moisture and made into t / ha. When done the application of pesticides in the V8 stage of corn was noted positive effect of all pesticides used in the severity of white spot, however, the fungicide mancozeb in dosage 2500 g.p.c./ha showed superior control of disease in these conditions, effect this resulted in an increase of 100% productivity. The application of pre-flowering assessed by AUDPC showed efficiency of all pesticides used at this time, but the mixture epoxiconazole + pyraclostrobin showed greater control of the severity of white spot of maize, which resulted in an increase of about 90% yield.