This study aims to evaluate the performance of four adjuvants types (polyoxyethylene alkyl phenol ether, polyether polymethyl siloxane copolymer, mineral oil, and soybean oil methyl ester) on the spray deposits, dose optimization and simulated rainfastness resistance after application of the diquat herbicide in Euphorbia heterophylla weed. The spray deposits verification will be performed by spraying the Brilliant Blue dye associated with the herbicide and the adjuvants. The deposits values in µL g-1 of aerial dry weight (ADW) will be submitted to ANOVA and the averages compared by the SNK test (p <0.05). The distribution uniformity data will be adjusted to the regression by the Logistic model. To verify the effect of adjuvants in the control of E. heterophylla the herbicide diquat will be sprayed at doses of 3600; 1200; 400; 133; 44; 15; 5 and 0 (control without herbicide) g of a.i. ha-1. The assessments will consist of visual control and ADW. Dose-response curves will be determined using the logistic model by the statistical Software R. The treatments will be compared by the C50 and C90 values (dose required to provide 50 and 90% control or 50 and 90% reduction in ADW). The simulated rainfastness resistance with an intensity of 10 mm at 10; 20; 40; 120; 240 and 480 minutes after spraying will be assessed by visual control and ADW with the treatments averages compared by the SNK test (p <0.05).
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