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Is resistance inevitable? Part II
Dr. Victor Martin

First the drought monitor remains basically unchanged. Harvest is slowly underway with corn and some soybeans. Grain sorghum is all over the place with maturity and the sorghum planted close to on time looks promising. Wheat and rye and being planted and some has emerged. The warm weather has helped move things along, however, next week’s forecast predicts a major cool down by the middle of this week. Last week we discussed herbicide resistance in weeds and how it develops. This week – can we do much about it and can we prevent it with newer herbicide chemistries?

• To answer the second question first, yes. As will be discussed below, using these techniques will allow new chemistries to be effective and remain so. The key for new products is to rotate modes of action, what kills the weed.

• Simple and to the point – start with a clean, weed-free seedbed and do everything possible to produce a vigorous actively growing crop that achieves full canopy as quickly as possible.  

• While expensive, new products are coming on the market with new modes of action. This doesn’t mean totally abandon products like glyphosate but using them in combination and rotation with other products. Some of the chemistries must be used in combination with varieties and hybrids specially developed for the herbicide and others not.

• Even with the expense, move beyond post emergence only herbicide programs and use a pre/post combination. And while taking rotational considerations into account, consider more soil applied residual herbicide.

• As much as is possible, weed control, especially of seedling weeds, must be an obsession. And even though no-till and conservation tillage acreage has suffered with herbicide resistance, move back to reducing tillage and where practical eliminate it. If weed pressure can be controlled for several years under this system, weed pressure starts to diminish. However, this can be difficult to accomplish with growing conditions.

• Use as diverse a crop rotation as possible, especially if broadleaves and grass crops can be used. In some areas, using a broadleaf crop may not be practical.

• Cover crops that can provide good ground coverage and then be terminated and left on the soil surface can help decrease weed pressure. This need not be an expensive cover crop blend. It can be something as simple as planting spring outs at several bushels per acre in the fall and letting them die out over the winter and then plant into the residue.

• Finally, while not a great option – a fallow period with super aggressive weed control (chemical, mechanical, or a combination) for those severely infested fields.

Dr. Victor L. Martin is the agriculture instructor/coordinator for Barton Community College. He can be reached at 620-792-9207, ext. 207.