Posts Tagged ‘herbicide injury’

Herbicide Carryover Concerns from Dry Weather

Thursday, July 21st, 2011

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

The lack of rain this summer could impact herbicide carryover in dryland fields. Most herbicides require moisture to degrade in the soil (water needed for both microbial and chemical breakdown). In typical summers we get adequate rainfall for this breakdown to occur. Last summer was dry and we observed herbicide carryover from a summer application in fall planted small grains. Be sure to read the labels of products applied this summer and evaluate the carryover potential.

Herbicide Rotation Restrictions

Friday, March 11th, 2011

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Herbicide rotational restrictions or guidelines are based on two criteria; regulatory and biological. Both of these criteria are equally important to the end user of the commodity and can be justification for rejecting the harvested product. Maximum residue levels are determined based on a range of tests and studies. Residue levels are determined to ensure that they are below a level that could cause an effect. Biological criteria are established to ensure the succeeding crops aren’t adversely impacted. It is critical that the pesticide label is read and understood before application. It does not matter whether the rotational restrictions were determined based on regulatory or biological criteria, the label needs to be followed. Rotational restrictions are often changed on the labels with little to no publicity, so review pesticide labels every year to be sure you are in compliance with the label.

Where we seem to have the biggest issue with rotational crops is with double cropped vegetables. Products used in sweet corn, peas, or other early-season crops can limit what can be planted after harvest.

Clean Out the Sprayer

Friday, June 11th, 2010

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

I have had a number of fields this year that were injured from low rates of herbicide remaining in the tank from the previous application. Most of these situations occur when the spray is mostly sprayed out and rather than rinse out the tank, additional water is added with the thought that “the little amount that remains will be diluted enough”. In cases with a highly sensitive crop, and in combination with a translocated herbicide, severe injury can occur. Also, a crop that is developed to be resistant to one herbicide, does not make it resistant to all herbicides (i.e. Liberty Link is not resistant to glyphosate). When in doubt, clean out.