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Farmer perceptions of herbicide resistance Iowa State University Weed Science
(March 12, 2002 -- CropChoice news) --It is generally acknowledged that the world's worst herbicide resistant weed problems are found in the wheat producing areas of Western Australia. Annual ryegrass is the predominant resistant weed in this region, and has developed resistance to most herbicides available for use in wheat.
In response to these problems the Australian government has initiated a large program to study the biology of resistance and the influence of agricultural practices on the problem. A large effort is being made to understand why farmers make decisions that may influence the likelihood of resistance developing on their farms. Rick Llewellyn and others recently summarized results of an extensive survey of farmer' attitudes toward resistance. This report is posted on the web at: http://www.general.uwa.edu.au/u/dpannell/dpap0113.htm.
In this article I will summarize a few of the findings of this study, readers are encouraged to go to the original article for complete results. More than 130 farmers were surveyed in two regions of Western Australia, one in which resistance is widespread and the second where serious infestations of resistant weeds are sporadic. The researchers wanted to determine the farmer's understanding of herbicide evolution in terms of herbicide use patterns. Farmers were asked how many applications of an ACC-ase inhibitor would be required to select for resistant biotypes in ryegrass. The mean response for both regions was six applications. A higher percentage of farmers from the region with low resistance predicted greater than eight applications compared to farmers from the region with widespread resistance. Research has shown that resistance is likely to develop with less than eight applications of these herbicides. The prediction for number of glyphosate applications needed to select for resistance was 16. Farmers from the area without severe resistance were more likely to suspect it would take the same number of glyphosate applications as ACC-ase inhibitors to develop resistance than farmers with first-hand experience with resistance.
Experience has shown that the likelihood of resistance is less with glyphosate than the ACC-ase inhibitors. This finding indicates that farmers from regions experiencing resistant problems are more aware of current issues regarding herbicide resistance.
There has been debate on whether the development of herbicide resistance imposes a cost to the grower. Australian farmers expected annual returns on land where resistance eliminated all herbicide options to decline by 37 to 50%. To further evaluate the perceived cost of resistance, farmers were asked the price they would be willing to pay for land with different levels of herbicide resistance. The presence of resistance to only ACC-ase inhibitors reduced land value by approximately 15%. Resistance to both ACC-ase and ALS-inhibitors reduced the perceived value of land by 25%. In the area with widespread resistance, farmers stated that the presence of resistance to the ACC-ase, ALS and glyphosate herbicides would reduce the value by more than 50%. I am not aware of any similar studies conducted in Iowa or other states, but I suspect the results would indicate that herbicide resistance has little impact on land value. This is probably due to the wider selection of herbicides available for use in corn and soybeans.
The farmers surveyed were aware of herbicide resistance and the likely number of herbicide applications required to select for resistance. However, a significant percentage of farmers held misconceptions concerning resistance. These included:
Source: AgNet
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