Drop deposition on canopy and chemical control of Phakopsora pachyrhizi in soybeans
Abstract
Drop deposition on soybean canopy with three spray nozzles and chemical control programs of asian soybean rust were evaluated in two soybean cultivars, in a study carried out in Itaara, RS. The treatments were arranged under completely randomized block design with four replications, in a factorial design 2 × 3 × 3, utilizing two soybean cultivars, three spray nozzles and three chemical control programs. The fungicide applications were accomplished in R1 and R4 growth stages. Drop density, volumetric medium diameter (VMD), leaf area index (LAI), disease severity and grain yield were the variables measured. Based on the severity data of asian rust the area under disease progress curve (AUDPC) was calculated. The spray nozzles studied were significantly different in relation to drop deposition on soybean canopy, VMD, AUDPC and grain yield. The soybean grain yield was increased by 53.17% on Asgrow 8000 RG and 29.89% on Agiara RR cultivar, as a result of fungicide application. The LAI of cultivars influenced drop deposition and penetration into canopy.