Weeds

Almost all postemergence soybean herbicides have a preharvest interval or a soybean developmental stage beyond which applications cannot be made specified on their respective label.  Labels of some products may indicate both a developmental stage (before soybean bloom, for example) and a preharvest interval.  Preharvest intervals indicate the amount of time that must elapse between the herbicide application and crop harvest.  Failure to observe the preharvest interval may result in herbicide residue levels in the crop in excess of established limits. …

Waterhemp continues to be one of the most widespread and troublesome broadleaf weed species with which Illinois farmers must contend.  Factors related to the species’ biology, such as prolonged germination and emergence, obligate outcrossing, and high seed production, contribute to management challenges.  The evolution of herbicide resistance in Illinois waterhemp populations adds another very challenging obstacle for effective management.  Recently, many have sent questions and concerns regarding the inability to control waterhemp with various postemergence soybean herbicides. …

We would like to take this opportunity to once again extend the invitation to attend the 2016 University of Illinois Weed Science Field Research Tour, to be held Wednesday, June 29th 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.  The tour will provide ample opportunity to look at research plots and interact with weed science faculty,…

The labels of most postemergence corn herbicides allow applications at various crop growth stages, but almost all product labels indicate a maximum growth stage beyond which broadcast applications should not be made, and a few even a state minimum growth stage before which applications should not be made.  These growth stages are usually indicated as a particular plant height or leaf stage; sometimes both of these are listed.  For product labels that indicate a specific corn height and growth state,…

The springtime color scheme provided by winter annual weed species in many no-till fields has shifted from the hearty purple of flowering henbit and purple deadnettle to the bright yellow flowers of two species.  Yellow rocket and cressleaf groundsel (a.k.a. butterweed) both produce bright yellow flowers and are common across much of the southern half of Illinois.  Although flower color is similar, the plants are distinct species.  Most of the yellow-flowered plants currently in fields is butterweed.…

We invite you to attend the 2016 University of Illinois Weed Science Field Day on Wednesday, June 29th 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.…

Marestail can be one of the most challenging weeds to control prior to planting no-till soybean.  Already this season some have reported poor marestail control following applications of glyphosate plus 2,4-D.  Poor control can be caused by several factors, including large plant size and resistance to glyphosate.  If a marestail population is resistant to glyphosate, a pint of 2,4-D in the spring is generally inconsistent/ineffective when it’s the only product in a tankmix active on the resistant population.…

The following information about cover crop termination is taken from the 2016 Weed Control Guide for Ohio, Indiana and Illinois.  The information was originally written by extension weed scientists at Purdue University.
Cover crops are unique in that most are planted primarily to reduce soil erosion and otherwise enhance soil quality, and are not harvested for their seed, fruit, or forage (although some are grazed or used as forage). Instead, cover crops are terminated before planting of summer annual grain crops such as soybeans and corn.…