CORESTA Congress, Online, 2022, Agronomy/Phytopathology Groups, AP 11

Evaluations of modern spray nozzle technology for maleic hydrazide application

(1) Department of Crop & Soil Sciences, North Carolina State University, Raleigh, NC, U.S.A.; (2) Department of Biological & Agricultural Engineering, North Carolina State University, Raleigh, NC, U.S.A.

Maleic hydrazide (MH) remains a critical component of sucker control programs in US tobacco production systems. However, MH residues remain a strong critique of tobacco sourced from the region. The purpose of our research was to evaluate medium and high-output nozzles (234 - 468 L ha-1) with ultra-coarse droplet size (> 650 microns) for their impact to sucker control efficacy and cured leaf residues in three stalk positions (cutter, leaf, and tip). Three ultra-coarse nozzles were selected: TurboDrop XL® (TDXL), Air Induction Turbo Twinjet (AITTJ) and Turfjet (TJ) and compared to the grower standard three-nozzle sucker control arrangement (outfitted with three solid cone nozzles) and a single solid cone nozzle. Each nozzle type and configuration was evaluated at 234 and 468 L ha-1 solution volumes. A non-treated control was included to establish sucker control parameters but was not included in the data analyses. Sucker control was > 97 % among each treatment combination (nozzle type × output volume); however, the TDXL (468 L ha-1), AITTJ (468 L ha-1), AITTJ-(234 L ha-1), and TJ (234 L ha-1) increased sucker control above the current grower standard. Cured leaf MH residues were similar among nozzle types in the cutter and leaf stalk position, but were lowest in tip leaves when the AITTJ and TJ nozzles were used. Cured leaf MH residues were also greater within the 234 L ha-1 solution volume than the 468 L ha-1 solution volume across each of the three stalk positions. Our results suggest that growers might utilize new nozzle technology in an attempt to lower MH residues in cured tobacco, but they should not change the recommended solution output volume of 468 L ha-1. Our results also suggest that in situations where growers do not have restrictions with MH residues, they may consider the 234 L ha-1 solution volume in an attempt to reduce the number of times they have to fill sprayer tanks.