Callaway County
Callaway County
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Jarman's Weekly Agronomy News August 2, 2000 |
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Drift and Carryover are the Primary Causes of Herbicide Injury |
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Incorrectly applied herbicides can hurt more than they help. Herbicide injury issues in corn and grain sorghum, including damage from carryover, drift, improper equipment calibration and failure to follow label directions. Problems from mis-application have been increasing over the last couple of years. Different types of herbicide cause different sorts of injuries. There have been numerous reports this year of fomesafen carryover in corn and grain sorghum. Fomesafen herbicides include Reflex and Flexstar. A few instances of this has been seen in the past but not nearly as widespread as seen in 2000.The carryover problems were most common in northeast Missouri although mid-Missouri had their share. Carryover injury usually occurs because the rotational interval of 10 months before planting corn or 18 months before planting grain sorghum is not observed, or because of boom overlaps or on ends of fields where the application rate has been doubled. The use of these herbicides has grown markedly in the past couple of years, because it works well against waterhemp and morningglory, two of the biggest problem weeds in Missouri. Increased use and the inability of fomesafen to break down quickly under aerobic soil conditions contributed to the carryover problems. We need saturated soils for anaerobic conditions so the microbes can work and break it down. Extremely dry conditions throughout last year and into late spring promoted carryover. Farmers were not able to get away with pushing the rotational interval this year. Fortunately, glysophate drift, a major cause of herbicide injury last year, has been less common in 2000, although it's still a pretty big issue. Roundup is the most common glysophate-based herbicide. It most commonly is spread to other fields by drift or by spray tank contamination. The corn will turn purple and die very quickly. Other herbicide injury problems can arise when producers apply photosynthesis inhibitors (atrazine, Sencor, Karmex, Lorox, Sinbar, Basagran, Buctril, and Tough to name a few) under cool, cloudy conditions or in high pH or sandy soils. When you walk into any given field, there is usually more than one problem. It's easy to blame it all on herbicide injury, but there might be three or four other sub-lethal things going on like poor fertility, insects, disease, weather, soil compaction, or others. The Source for this article is Bill Johnson, Assistant professor of Extension Agronomy and Weed Science at the University of Missouri - Columbia, (573) 882-2001. Upcoming Events to catch are the "Sunflower Field Days" August 9, 2000 at the Bradford Farm and August 10, 2000 at Sedalia, call 573-449-8638 for more information; and the University of Missouri Research Farm tours to be held at the Greenley Research Center - Novelty on August 3; the Graves Memorial Experiment Center - Corning on August 22; the Delta Center - Portageville on August 31; the Thompson Farm - Spickard on September 7; the Hundley-Whaley Farm - Albany on September 7; the Southwest Research Center - Mount Vernon on September 8; the Wurdack Farm - Cook Station on September 15; and the Forage Systems Research Center (FSRC) Pasture Days - Linneus on September 28.
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