Weeds

We invite you to attend the 2015 University of Illinois Weed Science Field Day on Wednesday, June 24th at the University of Illinois Crop Sciences Research and Education Center, located immediately south of the main campus. Coffee and refreshments will be available under the shade trees near the Seed House beginning at 8:00 a.m.
Similar to past years, we will car pool to the fields where participants can join in a guided (but informal) tour format.…

The rapid progress of corn planting sometimes can outpace the application of soil-residual herbicides.  In most instances these herbicides are applied within a few days after planting, but weather-and equipment-related factors can delay applications until after corn has emerged.
Most, but not all, soil residual herbicides can be applied after corn has emerged.  Products such as Balance Pro, Radius, Fierce, Prequel, Sharpen and Verdict must be applied before corn begins to emerge; applications of these products to emerged corn can result in significant corn injury. …

Many individuals involved in production agriculture have first-hand experience with the numerous challenges caused by herbicide-resistant weeds.  The magnitude of herbicide resistance is best measured on a worldwide scale.  The most recent summary indicates 450 unique cases of herbicide resistance—encompassing 245 species—occur globally.  Approximately 11–12 cases of unique resistance are discovered each year.  Methods employed to detect and study the evolution of herbicide resistance have improved greatly over time, but our understanding of the epidemiology of herbicide resistance has lagged.…

The harsh realities of poor marestail control with burndown herbicides applied before soybean planting were widespread during the 2013 growing season.  We anticipated even more challenges with this species for the 2014 growing season, but by and large the forecasted marestail “train wreck” did not materialize in much of the state.  Fall herbicide applications coupled with a harsh winter that caused a high degree of mortality to winter annual weed species probably contributed to a reduced population of marestail last spring. …

The most recent report on the condition of the Illinois winter wheat crop indicated approximately 10% of the crop was rated poor or very poor, while close to 90% was rated fair to excellent.  It appears likely that much of the wheat crop will remain intact, but in other instances farmers might elect to terminate poorer stands and plant corn or soybean.  If the decision is made to plant corn or soybean into wheat stands where some plants remain alive,…

The 2008 edition of the Illinois Agricultural Pest Management Handbook was the final edition of a publication that served pest management practitioners for many decades. Herbicide information and annual updates of product performance ratings were mainstays of that publication.  Since 2008 we periodically have published herbicide performance ratings, but admittingly not with a great deal of consistency.  Recently, the weed science programs at The Ohio State University and Purdue University extended an invitation to the University of Illinois weed science program to join them in the production of their joint weed control publication. …

Herbicides applied in the fall often can provide improved control of many winter annual weed species compared with similar applications made in the spring.  Marestail is one example of a weed species that is often better controlled with herbicides applied in the fall compared with the spring.  An increasing frequency of marestail populations in Illinois are resistant to glyphosate, and within the past year we have confirmed that resistance to ALS-inhibiting herbicides also is present in Illinois populations. …

Accurate identification of weedy Amaranthus species during early vegetative stages can be difficult.  However, identification of the various species becomes much more reliable when reproductive structures are present (Figure 1).
Before harvest begins, consider taking a few minutes to scout fields; at this time of year it is much easier to differentiate between Palmer amaranth (Figure 2) and waterhemp plants (Figure 3).
Similar to waterhemp, Palmer amaranth plants are either male or female; male plants produce only pollen while female plants produce only seed. …