Weed management is field day topic
By Janet Kubat Willette
jkubat@agrinews.com
Date Modified: 08/13/2012 12:53 PM
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ROCHESTER, Minn. — Weeds were the primary focus of the University of Minnesota Crop Management Day held July 10 in Rochester.
University of Minnesota regional Extension educator Lisa Behnken outlined the growing season thus far. It started dry, giving farmers the ability to do tillage early. A bad flush of weeds occurred early.
Pre-emerge herbicides weren't as effective as in past years, probably due to dry conditions, Behnken said. It's a very good option to get ahead of weeds and have a residual effect that lasts into the growing season.
Farmers need to know what weeds are issues in their fields and select herbicides accordingly. In the field across from RCTC, ragweed is the issue and Authority First provides good control, as long as the ragweed is not ALS resistant.
University of Minnesota weed scientist Jeff Gunsolus talked about demonstration plots set up with the intention of training people to deal with resistant weed management as more resistant weeds are being documented.
Weed emergence and timing are an important part of the study.
Giant ragweed, common lambs quarter and water hemp are the three greatest problem weeds at the Rochester site. Ragweed and lambs quarter are early emerging weeds while water hemp emerges later.
If early emerging weeds aren't dealt with up front, a height difference occurs when post-plant herbicides are applied, which impacts control.
Advantages of applying a pre-plant herbicide include reducing weed density and increasing yield potential and reducing the weed species mixture and improving the herbicide and adjuvant compatibility because there are fewer weeds that must be controlled.
Applying a pre-plant herbicide results in a narrower distribution of weed sizes and improves the consistency of weed control. Further, it results in added value including increased nitrogen efficiency in corn and early season canopy in soybeans, Gunsolus said.
It's all about applying the right herbicide on the right weed at the right time, he said.
Spraying
University of Minnesota Extension educator Dave Nicolai talked about sprayer nozzles and drift management.
Keeping spray where it's intended is the goal. To reduce drift, Nicolai suggests lowering the sprayer boom height to 18 to 24 inches above the target. Also, avoid adverse weather conditions including sundown and sun up. Uses nozzles that produce droplets as large as practical to provide the necessary coverage, he said.
Beetles
IPM specialist Fritz Breitenbach advised producers to start looking for corn root worm beetles in their corn fields. The problem appears worse in corn-on-corn fields.
"Corn root worm appear to have had a very good year," he said.
It hasn't been a good year to activate corn root worm insecticide.
Micro-nutrient study
University of Minnesota soil scientist Dan Kaiser hopes to answer the questions he's getting on micro-nutrients through a field trial now underway.
The primary questions he receives are about sulfur and magnesium. As for sulfur, as long as farmers are taking care of sulfur for corn, it should be good for soybeans.
Alfalfa is sensitive to boron and it's bad if it's overapplied. Sugar beets and clover are also sensitive to boron deficiency. Corn and small grains are sensitive to copper deficiency and alfalfa, small grains, soybeans and sugar beets are sensitive to magnesium deficiency. Corn is sensitive to zinc deficiency.
In 2011, he didn't see any tie between yield and micro-nutrients. Drought capped yields.