Glyphosate Resistant Weeds?
Horseweed - Conyza canadensis
Two rapid, non-destructive tests have been developed by the United States Agricultural Research Service to test the effectiveness of glyphosate (the active ingredient in Round-up) on weeds that it is suspected are developing a resistance to the herbicide. In 2000, Horseweed, Conyza canadensis, became the first weed species to develop resistance to glyphosate in cropland where glyphosate-resistant soyabeans were grown. Glyphosate-resistant biotypes of Horseweed have now been confirmed in 13 states east of the Mississippi River. Glyphosate is effective at killing all plant types including grasses, broad-leafed weeds and sedges, as well as perennial and woody plants. After emergence, glyphosate-resistant crops are capable of tolerating multiple applications of the herbicide, while weeds are killed. However, repeated use over many years has left several weed species resistant to glyphosate. The two tests can be used together.
One method, which involves dipping a whole leaf into a glyphosate-based mixture and looking for signs of injury, is quick and easy to perform. To achieve double confirmation of the weed's status, a second assay can be used. This method takes advantage of glyphosate's mode of action, which involves inhibiting amino acid metabolism in what is known as the shikimic acid pathway. Leaf tissue samples are removed, and amino acid levels are measured with specialised laboratory equipment. If glyphosate resistance is confirmed, the tests should help reduce the spread of resistant Horseweed populations because growers will use different herbicides to manage the resistant weeds. While this research is directed at commercial growers, it is very relevant to home gardeners as weeds do not respect field or garden boundaries.
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Happy Gardening
Philip
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Two rapid, non-destructive tests have been developed by the United States Agricultural Research Service to test the effectiveness of glyphosate (the active ingredient in Round-up) on weeds that it is suspected are developing a resistance to the herbicide. In 2000, Horseweed, Conyza canadensis, became the first weed species to develop resistance to glyphosate in cropland where glyphosate-resistant soyabeans were grown. Glyphosate-resistant biotypes of Horseweed have now been confirmed in 13 states east of the Mississippi River. Glyphosate is effective at killing all plant types including grasses, broad-leafed weeds and sedges, as well as perennial and woody plants. After emergence, glyphosate-resistant crops are capable of tolerating multiple applications of the herbicide, while weeds are killed. However, repeated use over many years has left several weed species resistant to glyphosate. The two tests can be used together.
One method, which involves dipping a whole leaf into a glyphosate-based mixture and looking for signs of injury, is quick and easy to perform. To achieve double confirmation of the weed's status, a second assay can be used. This method takes advantage of glyphosate's mode of action, which involves inhibiting amino acid metabolism in what is known as the shikimic acid pathway. Leaf tissue samples are removed, and amino acid levels are measured with specialised laboratory equipment. If glyphosate resistance is confirmed, the tests should help reduce the spread of resistant Horseweed populations because growers will use different herbicides to manage the resistant weeds. While this research is directed at commercial growers, it is very relevant to home gardeners as weeds do not respect field or garden boundaries.
To read further gardening news from the News pages of the GardenMessenger web-site click here.
Happy Gardening
Philip
GardenMessenger
To join the GardenMessenger gardening community
click here.
To visit the GardenMessenger web-site
click here.
Directory of Gardening Blogs
posted by Philip Swindells | 8:25 AM
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