Recent innovations in spray nozzle technology may help applicators achieve effective weed control while reducing spray particle movement. Laboratory and field tests have shown the effectiveness of new nozzle types for reduction of spray drift. However, pesticide applicators are reluctant to switch to new nozzles because limited information is available on the effectiveness of these nozzle types for controlling weeds. Chemical labels provide little or no guidance on the use of using new nozzles. The major objective of this study was to evaluate the effectiveness of low-drift nozzles in weed control. We also investigated the drift and spray coverage from conventional and low-drift nozzles.
Field studies were conducted at three locations in 2003 to determine the effect of nozzle type and drift control adjuvant on herbicide effectiveness and spray particle drift. A field-size study was conducted near Tiffin, OH, and small-plot studies were conducted near South Charleston and Chesterville, OH, respectively, in 2003. At Tiffin and Chesterville, glyphosate was applied postemergence in glyphosate-resistant soybeans. The factors at these sites included nozzle type (XR Teejet at 40 psi, Turbo Teejet at 40 psi, AI Teejet at 40 and 60 psi) and drift control adjuvant (0 and 2.5 gal/100 gal spray mixture of Corral AMS Liquid, a liquid ammonium sulfate plus a polyacrylamide drift control adjuvant). At Tiffin, treatments were applied in a spray volume of 15 gallons per acre (gpa) with a commercial-sized Patriot sprayer using 0.3 gal/min nozzles. Plot size was 60 ft wide by 711 to 1212 ft long (length of field). Spray coverage at the canopy level and in the canopy (~ 2 inches above soil) was measured using 26 by 76 mm water-sensitive paper. GPS coordinates were used to mark at least two patches of each weed species evaluated per plot. Weed control was evaluated 28 DAT. At Chesterville, treatments were applied with a hand-held carbon dioxide-pressurized sprayer using 0.2 gal/min nozzles and a spray volume of 15 gpa. Plot size was 10 feet wide by 40 feet long. Weed control was evaluated 14 DAT.
In the study at South Charleston (at the OARDC Western Branch), treatment factors included nozzle type (XR Teejet at 40 psi, Turbo Teejet at 40 psi, AI Teejet at 60 psi), herbicide (glyphosate or a combination of fomesafen plus fenoxaprop plus fluazifop), and herbicide rate (recommended and 67% of recommended). An additional two treatments consisted of the drift control adjuvant with recommended rates of both herbicide treatments applied with the AI nozzle at 60 psi. Herbicides were applied postemergence to glyphosate-resistant soybeans with a tractor-mounted, carbon dioxide-pressurized sprayer using 0.2 gal/min nozzles and a spray volume of 15 gpa. Plot size was 10 feet wide by 65 feet long. Weed control was evaluated 26 DAT.
In the small-plot study at Chesterville, all treatments controlled at least 98% of the giant foxtail, giant ragweed, and common lambsquarters, and control was not affected by nozzle type or drift control adjuvant. In the field-size study at Tiffin, there was no significant interaction between nozzle type and drift control adjuvant, allowing comparison of main effects only. There was no difference in nozzle type or drift control adjuvant for control of Canada thistle and seedling dandelion. Nozzle type affected control of yellow nutsedge, common ragweed, and Venice mallow at an alpha level of 0.05, and control of common lambsquarters and velvetleaf at an alpha level of 0.1. Results were as follows for control of these weeds (where a nozzle type is not listed, that nozzle was not different than any of the other nozzles): yellow nutsedge - XR=AI (40 psi)>AI (60 psi); Venice mallow and velvetleaf - XR>AI (40 and 60 psi); common ragweed - XR=Turbo Teejet>AI (60 psi); common lambsquarters - AI (40 psi)=Turbo Teejet>XR. The addition of the drift control adjuvant did not affect common lambsquarters control, but reduced control of velvetleaf, Venice mallow, and yellow nutsedge at an alpha level of 0.05, and common ragweed at an alpha level of 0.1. The greatest reduction in control occurred for velvetleaf and Venice mallow, for which the addition of the drift control adjuvant reduced control from 85% to 59 and 64%, respectively. Wind speed and direction were extremely variable during herbicide application at Tiffin, and no differences were observed among treatments with regard to spray particle drift.
In the small-plot study at South Charleston, control of redroot pigweed was not affected by nozzle type, herbicide type, or herbicide rate. Glyphosate controlled giant foxtail and common lambsquarters more effectively than fomesafen plus fenoxaprop plus fluazifop regardless of nozzle type or herbicide rate. At recommended rates, there was no difference in the control of giant foxtail or common lambsquarters among nozzles within herbicide treatment. At 67% of the recommended rate, the AI nozzle was more effective than the Turbo Teejet nozzle on these weeds. At recommended rates, there was no difference in giant ragweed control between glyphosate and the fomesafen mixture with the Turbo Teejet and AI nozzles and with the glyphosate and XR nozzle treatment, however reduced control was observed for the fomesafen mixture and XR nozzle treatment.
Nozzle type and drift control adjuvant affected weed control with a large commercial sprayer, but not with small plot sprayers. In the commercial sprayer, glyphosate was generally more effective when applied with XR Teejet or Turbo Teejet nozzles, compared to AI nozzles. The addition of a polyacrylamide drift control adjuvant reduced the effectiveness of glyphosate on most weed species when applied with a commercial sprayer. These results indicate that adjustment of spray equipment or adjuvants to reduce drift can reduce herbicide effectiveness. However, some reduction in drift can be achived without sacrificing herbicide effectiveness (e.g use of Turbo Teejet nozzles).
For further information contact Jeff Stachler, Extension Associate, Horticulture & Crop Science or the Ohio IPM Office.
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