Author
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Egan Jr, John |
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Submitted to: Pennsylvania Vegetable Growers News
Publication Type: Abstract Only Publication Acceptance Date: 1/22/2014 Publication Date: 1/29/2014 Citation: Egan Jr, J.F. 2014. Herbicide-resistant crops, resistant weeds, and herbicide drift[Abstract]. Pennsylvania Vegetable Growers News. p. 1. Interpretive Summary: Technical Abstract: New herbicide-resistance traits in corn and soybean may bring new management challenges for fruit and vegetable growers in the Mid-Atlantic region. Herbicide-resistant crops are an important weed management technology in row crop agriculture that allow growers to apply an herbicide to control weeds without harming their crop. Glyphosate-resistant crops (i.e. Roundup Ready) have been the most commercially successful herbicide-resistant crops, and these varieties have been planted over millions of acres, including much of the soybean acreage in the Mid-Atlantic. Over-reliance on the herbicide glyphosate in these crops has resulted in the evolution of difficult to control glyphosate-resistant weeds. In the Mid-Atlantic, glyphosate-resistant horseweed (or marestail, Conyza canadensis) is the most problematic species and is prevalent throughout the DelMarVa area and southeastern Pennsylvania. Glyphosate-resistant Palmer pigweed (Amaranthus palmeri) was also recently identified in Delaware and Pennsylvania and could become a serious problem. Biotechnology companies are developing crops with resistance to additional herbicides as a partial solution to challenges with glyphosate-resistant weeds. For instance, Dow AgroSciences is developing corn and soybean varieties with combined resistance to glyphosate, glufosinate, and 2,4-D. The Monsanto Company is developing soybean with combined resistance to glyphosate and dicamba. These varieties could be on the marketplace as early as 2015 and may become very popular with soybean growers dealing with glyphosate-resistant weeds. Both dicamba and 2,4-D are in the synthetic-auxin class of herbicides. These compounds can be prone to drifting off crop fields and are frequently cited in incidents of herbicide damage to non-target vegetation. Horticultural crops (especially grapes, tomatoes, peppers, cucurbits, and snap beans) are sensitive to dicamba and/or 2,4-D at the low doses typical of herbicide drift. When exposed to synthetic-auxin herbicide drift, injury on horticulture crops can be easily recognized by symptoms including leaf cupping and twisting stems. Plant response to these herbicides can vary based on a number of factors including plant growth stage and environmental conditions at the time of exposure. Plants exposed to dicamba or 2,4-D drift during early vegetative stages can often fully recover from seemingly serious injury symptoms, especially during favorable growing conditions. Exposures during flowering or fruit set are often more serious and can result in substantial yield loss. Herbicide drift can also damage ornamental plants, and wildflowers exposed to synthetic-auxin drift may show reduced production of flowers that support pollinators and other beneficial insects. Row crop producers and herbicide applicators have numerous options to prevent herbicide drift. Herbicide drift can be effectively reduced by using drift-reducing spray nozzles, limiting the speed of application vehicles, applying herbicides only under appropriate low-wind conditions, and using low-volatility herbicide formulations. Horticultural producers can minimize risks from herbicide drift by talking with neighbors that may be using synthetic-auxin herbicides, learning to recognize injury symptoms, and reporting a significant injury event as soon as it is spotted. |
