Influence of spray volume on the control of Conyza spp. in soybean pre-sowing with burndown.

The herbicide mixture diclosulam + halauxifen appears to be an alternative for the control of Conyza spp.; however, the spray volume may result in different spray deposition effects on the target and, therefore, on the control. Therefore, the objective of this study was to evaluate the impact of different spray volumes of diclosulam + halauxifen on the control of and damage to the leaf surface of Conyza spp. The experiment was conducted in the field in a randomized block design with four replications. Diclosulam + halauxifen (23.52 g ai ha-1 + 6.32 g ae ha-1) was applied to Conyza spp. at average heights greater than 10 cm, followed by sequential application of glufosinate ammonium (500 g ai ha-1) after 14 days. Different spray volumes (200, 150, 100, 80 and 50 L ha-1) were used. The percentage of droplet coverage was evaluated using hydrosensitive paper and analyzed using DropScan software. After 24 hours of initial application, the leaves were collected for scanning electron microscopy (SEM). Although the different spray volumes did not affect the control, faster necrosis effects were observed at 150 and 200 L ha-1. Moreover, the trichome and stomatal density decreased at a spray volume of 200 L ha-1, indicating greater initial damage at this spray volume. Thus, increased spray spray volumes result in increased spray spray deposition, damage to leaf structures and consequently increased control speed.