What to Watch for from the Combine to Improve Weed Management - UNL CropWatch, Sept. 30, 2011

What to Watch for from the Combine to Improve Weed Management - UNL CropWatch, Sept. 30, 2011

Sept. 30, 2011

With harvest in full swing, many farmers are probably reflecting on the season, and some are considering what they’ll do differently next year. This is a good time to take a few notes on what you’re seeing and start planning for next year’s crops.

While in the combine, look for weed and insect problems to fix for next year. Harvest provides an opportunity for a final evaluation of your weed management program and to a lesser extent, your insect management program. As you travel over all of your fields, take a minute to record observations such as where weeds are present. Be sure to note the exact locations and details so you know how to correct it for next year.

The next step of being a “crop scene investigator (CSI)” is to make the linkages and relate weed or insect problems with management decisions that were made. Use your yield monitor to help identify or confirm these problem areas.

Former UNL Extension Weeds Specialist Alex Martin once provided the following on weed management assessment at harvest.

Post-treatment Weeds.  Small grass and broadleaf weeds are likely to have developed after the first month of the growing season, perhaps after a post-emergence treatment or cultivation or after a pre-emergence treatment has become ineffective. These smaller, late developing weeds may produce seed and perpetuate the problem but are unlikely to have impacted yield. These weeds are most likely in areas where the crop canopy developed more slowly, allowing penetration of the light necessary for weed establishment. Large weeds present at harvest likely are escapes which were not controlled by your primary weed management program. Depending on the number of these weeds, a change may be indicated for your weed management program.

Learn more

about combating herbicide resistance in weeds.  See CW story

Possible Resistant Weeds.  You may be able to see indications of herbicide resistance at harvest although the picture would have been clearer with an earlier examination. Herbicide resistance is first evident as a limited number of escapes in the field. There are many causes of weed escapes other than herbicide resistance. The key is to look for scattered large plants or small patches that were not controlled by your primary program. Dead weeds adjacent to the large ones provide even more evidence that resistance may be present. These fields should be monitored closely the next year.

Weed Patches.  These indicate that your weed management program is not uniformly effective across the field. There may be several causes, however the effect is the same—these field areas will have higher concentrations of weed seed as compared to the rest of the field. This means the problem next year will be most serious in these patches. If you continue to manage the field as in the past, the patches will persist or become larger. A change in management is needed to prevent “growing” these weed patches.

Perennial Weeds.  These typically occur in patches and many are less susceptible than annuals to most weed management programs. Perennials usually call for special attention not warranted on the entire field. Identifying problem areas in the fall can make it easier to target them in the spring.

With a little extra effort at harvest you can gather information that will be useful in developing next year’s weed management program.

Brandy VanDeWalle
Extension Educator in Fillmore County


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