University of Illinois, Urbana-Champaign: News

Aaron Hager, professor of crop sciences

8/18/2014  8:00 am

Despite an unusually cold Midwest winter and cooler-than-average spring, near-ideal growing conditions in 2014 have boosted the growth of crop plants, garden vegetables, flowers, lawns – and weeds. Crop sciences professor and weed expert Aaron Hager spoke to News Bureau life sciences editor Diana Yates about weather and weeds.

Are any unusual weed problems arising this year in Illinois as a result of the lovely weather?

image of professor aaron hagerThe suite of weeds that we see in Illinois this year actually is quite similar to what we often encounter in a typical growing season. The abundant precipitation that many areas of the state received earlier in the season helped many weeds get off to a fast start, and they have flourished quite well so far. Many people would agree that last winter was a bit more challenging to bear than recent winters, but one positive outcome was that the persistent cold helped reduce the populations of many weed species that germinate during the fall, overwinter in vegetative stages, and resume growth in spring.

What conditions make invasive weeds even more problematic?

There are many conditions, but these often depend on the individual species. Some prefer hot and dry conditions, while others require cooler temperatures and more abundant moisture. Not being vigilant for these species during the early stages of infestation can allow them to become well established, which often makes subsequent efforts to control or eradicate them even more challenging and expensive.

Once the soybeans are setting pods and the corn is tasseled, what can farmers do to combat those weeds that remain in their fields?

At advanced stages of crop development, there are few herbicide options that farmers can use to control these usually large weeds. Perhaps the most consistent method to reduce the amount of seed these surviving weeds produce is to physically remove them from the field. This often involves a hoe or weed hook and several hours of labor, but by not allowing surviving weeds to add seed to the soil seedbank, farmers can realize an excellent long-term investment on any parcel of farm land.

You’ve written and spoken a lot about Palmer amaranth, a weed that can be particularly devastating if it gets a toehold in farm fields. How does the Palmer amaranth problem in Illinois this year compare to other years?

We have discovered more populations of Palmer amaranth in Illinois this season, and anticipate finding even more now that the plants have reached the reproductive stage of development. In 2014, we were able to conduct our first field research with an established population of Palmer amaranth. We hosted a field tour of our research plots toward the end of July, and approximately 450 people attended the tour, by far the largest attendance at any weed science field tour in the 21 years I’ve worked at the University. For many of them, that was their first encounter with this species. Unfortunately for some, it probably won’t be their last encounter with Palmer amaranth.

What about homeowners with vegetable or flower gardens? How vigilant should they be about reducing the spread of weeds?

Regardless of whether it’s a farmer’s field or homeowner’s garden, plant species that are considered weeds do very little to benefit the plants we are intentionally growing. Each area of land has only a finite amount of resources available to support plant growth, and any resources used by weeds are resources unavailable to support the growth of the desired plants or crops. Maximizing the yield of a 40-acre cornfield or backyard sweet corn patch requires the minimization of the weed’s adverse impacts.