POAST AND FUSILADE 2000 PHYTOTOXICITY AS INFLUENCED BY ADDITIVES

INTRODUCTION
Postemergence herbicide use continues to increase as indicated by the annual sugarbeet growers survey. Postemergence herbicides can be used alone, but often are tank-mixed with additives to improve their efficacy. Benefits of additives may include enhanced target coverage, greater uniformity of application, improved foliar penetration and increased selectivity. Petroleum oil, crop origin oils, and fertilizer salts as additives with postemergence herbicides have enhanced annual grass and broadleaf weed control. Some researchers have reported promising results when tank-mixing Basagran with 28% nitrogen solution for velvetleaf control in soybeans. Very limited information exists on potential benefits of fertilizer salts alone or in a tank-mix with petroleum oil and Poast or Fusilade 2000. Optimizing the additive content could be an effective method to improve the efficacy of Poast and Fusilade 2000.

MATERIALS AND METHODS
Field research was initiated in 1986 near Glyndon, Minnesota to evaluate additives with Poast and Fusilade 2000. 'Maribo Ultramono' sugarbeets, 'Siberian' foxtail millet, 'Steele' oats, and 'Marshall' wheat were planted as bioassay species in strips across plots on May 6 and July 25, 1986. Herbicides with additives were applied on June 4 and August 25 with a tractor mounted sprayer delivering 8.5 gpa spray solution at 35 psi through 800L nozzles when sugarbeets had four to six leaves, foxtail millet had four to eight leaves, oats had four to eight leaves, and wheat had four to eight leaves. Petroleum oil with 17% emulsifier (PO), sunflower oil + 15% Co-630 emulsifier, methylated sunflower oil + 15% C0-630 emulsifier (sunflower NE), 28% urea-ammonium nitrate (28% WAN), 10-34-0 liquid fertilizer, and ammonium sulfate were applied alone and in single or multiple combinations with postemergence herbicides.

RESULTS
Fusilade 2000 at 0.09 lb/A with petroleum oil or sunflower ME at 1 qt/A as single additives tended to give the greatest foxtail millet, oats, and wheat control (Table 1). Fusilade 2000 with fertilizer salts gave less control than petroleum or crop origin oils regardless of bioassay species. Fusilade 2000 tank-mixed with petroleum oil plus ammonium sulfate (0.09 lb + 1 qt + 2.5lb/A) provided 84 and 991 foxtail millet and oats control, respectively, or better control than either additive used singly with Fusilade 2000. Fusilade 2000 with petroleum oil plus 28% UAN at 1 qt + 1 gal/A gave control similar to ammonium sulfate plus petroleum oil with Fusilade 2000. Additives with Fusilade 2000 did not influence wheat control. No sugarbeet injury was observed with Fusilade 2000 and additives. More emphasis was placed on grass control evaluations in 1986, as the sugarbeets and bioassay species were at a larger growth stage than what would normally occur under field conditions. Other researchers have reported very good sugarbeet safety from Poast or Fusilade 2000 and petroleum oil at the 1 to 2 leaf stage. Poast or Fusilade 2000 and Betamix will be tank-mixed with additives and applied to sugarbeets at the 1 to 2 leaf stage in 1987.

Poast at 0.11 lb/A with 1 gal 28% UAN provided the greatest foxtail millet control when additives were applied alone with Poast (Table 2). However, Poast plus UAN gave less control of oats and wheat than Poast plus petroleum oil or sunflower oil. Poast plus ammonium sulfate, sunflower ME and petroleum oil as single additives, gave similar but less foxtail millet control than Poast plus UAN. Oats and wheat control was greatest with Poast at 0.11 lb/A plus single additives of petroleum oil or sunflower ME. Control of oats and wheat with Poast plus fertilizer salts was less than when Poast was combined with petroleum oil or crop origin oils. Poast tank-mixed with petroleum oil and fertilizer salts gave or tended to give better foxtail millet, oats, and wheat control than Poast plus petroleum oil or Poast plus fertilizer salts. Ammonium sulfate plus petroleum oil, 28% UAN plus petroleum oil, 10-34-0 plus petroleum oil used with Poast gave similar control of foxtail millet control, oats, and wheat. However, ammonium sulfate plus petroleum oil tended to be more effective than 10-34-0 plus PO and 10-34-0 plus PO tended to be more effective than 281 UAN plus PO.

SUMMARY
Poast or Fusilade 2000 with petroleum oil or sunflower ME tended to provide the greatest foxtail millet, oats, and wheat control when additives were used singly. Tank-mixing petroleum oil and ammonium sulfate with Poast or Fusilade 2000 gave or tended to give the greatest control of foxtail millet, oats, and wheat. Except for Poast with 28% UAN for foxtail millet control, Poast or Fusilade 2000 plus fertilizer salts gave or tended to give less grass control than Poast or Fusilade 2000 plus petroleum oil or crop origin oils.

1986 Sugarbeet Research and Extension Reports, Volume 17, Pages 62-64.

Questions/Comments