Here is the list of the top 10 weeds in surveyed corn fields and the percent of surveyed field with the species:
9. Large Crabgrass-16%
8. Fall Panicum-18%
7. Yellow Nutsedge-22%
3. Prickly Sida-27%
2. Morningglory spp-45%
Below is the list of top 10 weeds in surveyed soybean fields and the percentage of the field with the species:
10. Yellow Nutsedge-11%
9. Fall Panicum-14%
8. Common Ragweed-16%
5. Common Cocklebur-22%
3. Prickly Sida-30%
2. Morningglory spp-33%
Still there are other weeds Missouri farmers should be on the lookout for during the 2013 planting and growing season.
Asiatic dayflower is on Bradley's shortlist of weeds to watch. This weed tolerates very high rates of glyphosate, up to 8 times the application rate, making it difficult to control. Bradley recommended that in soybean fields, farmers should look at pre-herbicides like Sencor, Zidua and Firstrate, along with post herbicides like Firstrate and Cobra.
Another weed making its mark on the state is palmer pigweed or palmer amaranth. The problem with control of palmer amaranth is its resemblance to waterhemp. Oftentimes it can go misidentified by farmers and crop advisors.
There are a few distinctions for palmer amaranth.
-Diamond shape leaves.
-Long petioles on mature leaves
-Visual white water mark on leaves
-Seedlings larger than waterhemp
-Poinsettia growth on leaves
Palmer can grow to great heights making it difficult to control at later stages. Bradley says the weed should be identified and treated early in the season.
He warms that there is a glyphosate resistant palmer pigweed in the southern states. So far, he has only seen the species along river bottoms, in sandy soils and Missouri's bootheel. "It is on the increase in the state," he said. "We need to be on the lookout."