Weeds

On June 3, the United States Court of Appeals for the Ninth Circuit issued their decision that effectively vacated the registrations of the dicamba-containing products XtendiMax, Engenia and FeXapan.  Since this ruling many questions have arisen, including the fate of these products already in the commercial channel.  During a recent conversation with officials at the Illinois Department of Agriculture, officials presented their interpretation of the court ruling as follows:
It is the current interpretation of the Illinois Department of Agriculture that the dicamba-containing products XtendiMax,…

Replanting soybean fields or areas of fields likely will occur after soybean stand loss to recent cold temperatures or saturated soil conditions.  The following are general reminders about dicamba application timings and restrictions for Illinois soybean.

• Air temperature restriction: do not apply approved dicamba-containing products if the air temperature in the field at the time of applications is greater than 85 degrees Fahrenheit or if the National Weather Service’s forecasted high temperature for the nearest available location for the day of application exceeds 85 degrees Fahrenheit. 

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Soil-residual herbicides are important components of integrated weed management programs.  Reducing the number of weeds exposed to foliar-applied herbicides helps reduce the selection intensity for weeds resistant to foliar-applied herbicides.  Residual herbicides applied with postemergence soybean herbicides also can reduce the need for a second postemergence application.  However, simply applying a soil-residual herbicide does not guarantee the product will provide the desired level or duration of weed control.  Many edaphic and environmental factors influence the level of weed control achieved by soil-residual herbicides.…

Ample soil moisture and warming temperatures are promoting rapid growth and development of many early-season weed species.  Most weeds currently growing in fields emerged last fall and successfully overwintered (winter annuals, biennials or perennials), but several early-season summer annual species recently have emerged.  Existing weed vegetation should be controlled before planting by utilizing tillage, herbicides, or a combination of tactics so the crop can become established under weed-free conditions.
Field scouting to identify the weeds present and their relative densities will provide the information needed to tailor a burndown herbicide program for any particular field. …

No sooner have many unpleasant memories of the 2019 growing season begun to fade than we find ourselves looking ahead to contemplating potential residual weed management challenges in 2020.
Winter Annual Weed Species
Delays in planting the 2019 crop often accompanied delays in controlling existing stands of winter annual weeds prior to planting.  The obvious and unwelcome result was that seed production by winter annual species likely was a high in 2019 as any spring in recent memory. …

The 2020 Weed Control Guide for Ohio, Indiana and Illinois contains 223 pages of weed management information, including weed response ratings for corn and soybean herbicides.  Information and recommendations for managing weeds in small grains and forages is included, along with specific information about and control recommendations for several problem weed species.  Printed and pdf versions of the 2020 weed control guide are available at: https://extensionpubs.osu.edu/2020-weed-control-guide-for-ohio-indiana-and-illinois/
 
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Approximately two weeks ago, only a few (11 reported as of July 16) dicamba-related complaints had been filed with the Illinois Department of Agriculture (IDOA), and some held aspirations that the magnitude of off-target issues would be less this year than during the two previous seasons.  Today, it appears those hopeful aspirations are being replaced by the harsh reality that the magnitude of off-target issues in 2019 might be either similar to or possibly exceed those of previous seasons. …

The weed science program at the University of Illinois invites all weed management practitioners to our annual weed science field tour on Wednesday, July 10.  Please note the tour will begin at our off-campus field location (“The Lost Forty”) which is located on Cottonwood Road (County road 1700 east) approximately one-quarter mile north of County road 1850 North (see map).
Registration will begin at 8:00 a.m. and refreshments (coffee, juice, and doughnuts) will be available.  Preregistration is not required,…

Nearly all herbicide labels (soil-applied or postemergence) have rotational crop intervals that specify the amount of time that must elapse between herbicide application and planting a rotational crop.  This becomes particularly important with late-season herbicide applications.  These intervals are established to reduce the likelihood that herbicide residues will persist in sufficient quantities to adversely affect the rotational crop.  Some herbicide rotational restrictions are based solely on time, while other factors, such as soil pH and the amount of precipitation received after herbicide application,…