Weeds

Earlier this month, we discussed advantages of and techniques for controlling emerged weed vegetation prior to planting.  Several winter annual weed species have reached maturity while others, such as cressleaf groundsel (Figure 1),
began to flower within the past 10 days across areas of central Illinois.  Control of these mature plants with herbicides or single passes of tillage equipment will continue to be challenging.
Preplant control is also needed for emerged summer annual grass and broadleaf weed species. …

A potential scenario of planting delays will be corn planted in fields where no soil-residual herbicide was applied.  If the corn has not yet emerged, the soil-residual herbicide can be applied as originally planned.  But, what if the corn has emerged and the soil-residual herbicide has not been applied?  Can the application proceed as planned, or will a different product need to be selected?  The answer depends on the respective herbicide.
Most, but not all, soil residual herbicides can be applied after corn has emerged. …

We invite you to attend the 2013 University of Illinois Weed Science Field Day on Wednesday, June 26th 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. …

Wet soil conditions have caused delays in both planting and efforts to control existing weed vegetation.  Much of the existing weed growth is comprised of winter annual species, such as common chickweed, henbit, purple deadnettle, etc., but emergence of several summer annual species also has begun.  The growth of all species has accelerated with warmer temperatures and abundant soil moisture.  Several species of winter annuals are flowering and could produce viable seed before they are controlled with either tillage or herbicides. …

A recent article published in this Bulletin by Dr. Mike Gray (“Soil Insecticide Use on Bt Corn Expected to Increase this Spring Across Much of Illinois”) provides insights and data that suggest the use of at-planting soil-insecticides in corn is likely to increase this season.  Many insecticide choices are available to farmers, but several of these could restrict the option to use certain corn herbicides.  Specifically, using an organophosphate (OP) insecticide at planting or after corn emergence could restrict the use of herbicides that inhibit either the ALS or HPPD enzymes. …

The continual evolution of weed species and populations resistant to herbicides from one or more mechanism-of-action families represents one of the most daunting challenges faced by weed management practitioners.  Currently in Illinois, biotypes of 12 weed species have been confirmed resistant to one or more herbicide mechanisms of action.  Resistance to herbicides that inhibit the ALS enzyme is the most common type of resistance in Illinois.  Waterhemp has evolved resistance to more herbicide mechanisms of action than any other Illinois weed species,…

Dicamba is a growth regulator herbicide that can be used to control existing weed vegetation prior to crop planting.   Several commercially-available products contain dicamba, but not all products are specifically labeled for application prior to crop (especially soybean) planting.  Clarity may be applied before planting no-tillage corn at rates ranging from 8 (on coarse soils or medium- and fine-textured soils with less than 2.5% organic matter) to 16 (medium- and fine-textured soils containing 2.5% or greater organic matter) fluid ounces. …

Ideally, soil-residual herbicides should provide several weeks of weed control but not persist long enough in the soil environment to cause damage to rotational crops.  Dry soil conditions, similar to what most of Illinois experienced during the 2012 growing season, often slow the rate of herbicide degradation and increase the potential for damage to rotational crops from herbicide carryover.  Some remember the dry growing season of 1998 and the problems encountered in 1989 due to the persistence of one or more soil-residual herbicides that did not adequately degrade in the dry soil conditions of 1988. …

Dr. Marshal D. McGlamery, Professor Emeritus of Weed Science at the University of Illinois passed away January 25, 2013 in Suffolk, Virginia. Dr. McGlamery was world renowned for his knowledge and expertise in weed management. His unique talents for communicating his extensive knowledge with individuals and audiences were equally renowned. During his 35-year career in the professorial ranks at the University of Illinois, untold numbers of students, farmers and agricultural professionals benefitted from Dr. McGlamery’s undaunted passion for helping others better understand and manage unwanted vegetation.…