Spray nozzle and adjuvant effects on the chemical control of soybean Asian rust

Spray nozzle and adjuvant effects on the chemical control of soybean Asian rust. This study aimed to optimize the chemical control of soybean Asian rust through the evaluation of fungicide deposition on the canopy with the use of different spray nozzles and spray volumes, in the presence or not of an adjuvant. A randomized complete-block design with four replications was adopted, in a factorial model (3 x 2 x 2): three spray nozzles (turbo flat fan, twin flat fan, and twin flat fan with air induction) and two spray volumes (200 and 250 L ha(-1)), with and without the use of dodecylbenzene adjuvant. Soybean cv. M-SOY 8001 was sown in no-tillage plots. After application of the fungicide, composed by a mixture of azoxystrobin+cyproconazole (200 g L-1 + 80 g L-1), at 0.3 L ha(-1) of commercial product, spray deposition on the plant canopy, rust severity, 1000-grain weight and yield were evaluated. The results showed that turbo flat fan and twin flat fan were better than twin flat fan with air induction in yield increase. The adjuvant increased the droplet deposition on top and middle parts of the canopy and soybean yield. The increase of spray volume from 200 to 250 L ha(-1) did not provide better Asian rust control and yield increase.