Last year’s  challenging growing season could have some spillover impact in the form of herbicide carryover, warns one weed extension specialist. And it’s something growers need to keep in mind as they make their plans for 2013.

We asked University of Illinois weed scientist Aaron Hager four questions about 2013 weed control and what could be in store for producers this growing season.

Q. How will the 2012 drought impact weed issues in 2013?
Aaron Hager: The dry conditions of 2012 have increased concerns about persistence of soil-residual herbicides into the 2013 growing season. Above-average precipitation over the winter will certainly be beneficial toward herbicide degradation, but if these conditions are not realized we should continue to be concerned about the potential for injury to rotational crops.

Q. Why are you concerned about herbicide carryover?
Most of the concerns with herbicide carryover are related to products applied either close to planting or late postemergence. Use of these products has been increasing over the past several seasons due to the increasing frequency of herbicide-resistant weed populations.

The dry conditions of 2012 were not always conducive for good performance of these products, but the need for these herbicides will be greater next season. Frequently poor performance of soil-residual herbicides this season allowed for additional weed emergence, which could have increased overall selection for resistance to foliar-applied herbicides. Thus, we hope to balance the messages of increased potential for herbicide carryover with the increasing need to utilize these types of herbicides.

Q. Did the drought help mask problems with herbicide-resistant weeds?
As the dry soil conditions persisted, it seemed that might have impacted/reduced weed emergence. We don’t have data to support this, but anecdotally it seemed that we didn’t encounter the number of weed emergence events we normally encounter. Perhaps part of this could be explained by the earlier-than-normal weed emergence caused by the warm, dry conditions in March. We noted the first waterhemp emerged in March at Urbana, which is not typical.

Q. What are your weed management suggestions?
Our suggestions for 2013 will continue to focus on a more diversified weed management program. We know years like 2012 have happened before and will happen again. Long-term weed management solutions are not as simple as including a soil-residual herbicide; this practice is a component of an integrated program. But we need to have contingency plans for when soil-residual herbicide performance is not as optimal as we would like. Herbicide rotation, trait rotation, scouting, utilizing more than one type of herbicide, mechanical control, etc. are weed management tools that we should consider whenever possible.