February 17, 2016

Preparing for Resistant Palmer and Waterhemp

It is not news that one of the major crop production issues in Nebraska is the rapid increase in herbicide-resistant and difficult-to-control waterhemp and Palmer pigweed.

Many Servi-Tech crop consultants have never relied only on glyphosate for weed control, even in the early years of the introduction of glyphosate-resistant corn and soybeans. Early preplant and pre-emerge residual herbicides have been used in many cases for good weed resistant management. However, even with these programs, harder-to-control waterhemp has continued to increase in our clients’ fields.

A number of neighboring fields that relied solely on glyphosate have surviving weeds that created an incredibly high number of seeds. Pollen drift is another issue that helps to spread the resistant weeds. Bottom line, these hard-to-control weeds do not stay put on certain fields, but eventually get spread around.

Hybrid seed corn production has aided in some selection of HPPD herbicide resistance. Because of the lack of diverse herbicide use in some seed corn inbreds, it is more difficult for 100 percent weed control fields.

If they haven’t already, crop consultants will be making a concerted effort to get out early preplant and burndown residual products with multiple effective modes of action that will control weeds. The best advice now is not to allow any of the problem weeds to emerge, because we do not know if they can be controlled effectively anymore. Residual overlay herbicides, applied at very early postemerge time, will be used more, especially in the weed resistant history fields. Again, these will be utilized to not allow any of the weeds to emerge. 

Properly timed postemerged herbicides will need to be applied before weeds get over 4-6 inches tall. Multiple modes of action, proper and effective surfactives and additives, and consistent spray volume and pressure must be used. An occasional in-season cultivation and field rogueing should not be out of the question from the systems approach to good weed control. 

With regular field checks and proper recommendations, good weed control is achievable, even with the increased levels of resistance issues.

For specific information on how this applies to your field, contact your personal Servi-Tech agronomist.