INTERACTION OF NOZZLE TYPE AND ADJUVANT ON DROPLET SPECTRA AND EFFICACY OF GLYPHOSATE, GLUFOSINATE, GLYPHOSATE PLUS CLETHODIM, AND GLYPHOSATE PLUS MESOTRIONE AND S-METOLACHLOR. Jon R. Kohrt*1, Greg R. Kruger2, James Reiss3, Bryan G. Young1; 1Southern Illinois University, Carbondale, IL, 2University of Nebraska-Lincoln, North Platte, NE, 3Precision Laboratories, Waukegan, IL (110)

ABSTRACT

Field and laboratory studies were conducted to determine the interaction of different nozzle types and adjuvant combinations on droplet spectra and herbicide efficacy. Nozzle types evaluated were an extended range flat fan (XR), turbulence chamber flat fan (TT), venturi extended range flat fan (AIXR), and venturi flat fan (GA). Spray solutions were applied in 94 L/ha with XR11004, TT11004, AIXR11003, and GA11003 nozzle types at 275, 275, 480, and 480 kPa, respectively. Herbicide treatments included glyphosate (860 g ae/ha of Roundup PowerMax), glufosinate (450 g ai/ha of Ignite), glyphosate (860 g/ha of Roundup PowerMax) plus clethodim (51 g ai/ha of SelectMax), and glyphosate & mesotrione &s-metolachlor (1050 & 105 &1050 g ai/ha of Halex GT) applied with six different adjuvant systems: hydoxypropyl guar polymer (HPG) plus ammonium sulfate (AMS); low rate HPG (LHPG) plus AMS; polyacrylamide (PA) plus AMS; low rate PA (LPA) plus water conditioner (WC); WC plus non-ionic surfactant (NIS) and phytobland base oil (PO); and WC plus NIS. Droplet size was analyzed with a SympatecHelos KF Analyzer which uses laser diffraction to determine particle size in a large range from 0.5 to 1230 microns. Water alone and each herbicide without adjuvant were included as treatments for droplet size analysis, but not evaluated for herbicide efficacy. Field applications were made with CO2 sprayer equipped on an all-terrain vehicle with a four-nozzle, side-mounted boom at 19 kph. Glyphosate and glufosinate increased driftable fines (droplets <210 microns) for all nozzles, whereas glyphosate plus clethodim and glyphosate plus mesotrione and s-metolachlor tended to decrease driftable fines compared with water. In general, the addition of an adjuvant to glyphosate or glufosinate further increased fine droplets for XR, AI, and GA nozzles. In contrast, the driftable fines were reduced by most nozzle- adjuvant combinations with glyphosate & mesotrione & s-metolachlor when compared to the respective nozzle with water alone. The combination of TT nozzles and HPG/AMS produced the lowest percentage of driftable fine droplets for each herbicide evaluated. Herbicide efficacy varied by nozzle and adjuvant combination, however, TT nozzles with HPG/AMS usually provided the optimal combination of drift management and herbicide efficacy. Drift reduction nozzles and adjuvants are critical tools for drift management. However, this research suggests that the extent to which these tools reduce the risk for drift management is further complicated by variability in herbicide efficacy from nozzle/adjuvant combinations. Further advancement in mitigating drift beyond the generalized recommendations of using drift reduction nozzles and adjuvants would need to consider the specific herbicide and the target weeds to determine the optimal spray delivery system.