Herbicide Application Checklist

Bruce Potter, Regional IPM Specialist, University of Minnesota Extension Service
(Reprinted from "IPM Stuff," Southwestern Minnesota)

Editor's Note: Although the following article was written within the context of field crops, all of the following principles, including Murphy's Laws, apply to vegetable crops as well.

As crops begin to emerge, early post and post emerge herbicides will be applied. Volumes have been written on the topics of herbicide efficacy and application. One of better of these volumes is UM Extension Publication, BU-03157-S, 2002 Cultural & Chemical Weed Control in Field Crops http://www.agro.agri.umn.edu/appliedweeds/ . Click on view PDF to view/print this fine document in its entirety.

The following lists several things to consider if you are trying to avoid complaints on lack of performance and crop injury. Yes, this applies to glyphosate also. Always refer to the label.

1. Check the crop - Make sure those Roundup Ready and LibertyLink crops ended up in the fields you planned. It also doesn't hurt to make sure the herbicide you're putting in the tank is labeled for the crop you plan on treating. Remember, other than typical corn and soybean herbicides, herbicide tolerant crops are tolerant only to particular herbicides. In other words, glyphosate applied to a hybrid tolerant to Liberty (glufosinate), but not to glyphosate, would rather quickly create a low yield situation.

2. Check crop stage - Since corn is growing at a very slow pace, we should not have as many problems this year with post emerge herbicides being applied to corn larger than labeled. This statement may be a subset of one of Murphy's laws.

3. Check weed species - Does the product you plan to use provide control of the weed species in the field?

4. Check weed stage- Determine if weeds are up and are not too large to be controlled when you're using an herbicide that relies completely or primarily on post emerge activity (e.g. glyphosate, lactofen). Large common lambsquarters, for example, can be tough, especially under dry or cold conditions. This year there will be a wider spread than usual in development of early emerging weeds and those needing more heat to emerge.

5. Check herbicide and adjuvant - Have you have added the correct type and amount of adjuvant for the herbicide(s) used and have mixed the correct rate of herbicide?

6. Make sure the volume and pressure are appropriate for chemicals used. Sprayer calibration always makes weed control, crop safety, and economic sense

7. Check compatibility of tank mix partners and mixing order on labels. Some create your own tank mixes (and you know who you are) can provide excellent weed control. They might also create some interesting crop injury or an interesting sludge in the tank and nozzles. Check insecticide and herbicide labels when applying Callisto and ALS (e.g. Accent) corn herbicides after Organophosphate rootworm herbicides (Counter and Lorsban).

8. Check the weather. Performance of some herbicides is reduced when weed growth is slowed by cool weather or by drought. Crop injury from growth regulator herbicides (e.g. 2,4-D and dicamba) can be increased under very cold or very warm conditions. Although weed control is increased, so is crop injury from ALS herbicides under hot, humid conditions. Check rain fast periods if the weather is threatening. These rain fast periods are listed on labels and are also available in the aforementioned Cultural and Chemical Weed Control in Field Crops publication. Remember that herbicides can drift and watch for inversions. The latter may be less of an issue after we have Roundup Ready everything. Out here on the windy prairie a good spray day can be hard to come by.

9. Check whether the sprayer tank and boom are clean. This is especially important when switching between crops. Some herbicides and adjuvants work well as tank cleaners.

For more about IPM action in Southwestern Minnesota, refer to (and bookmark!) Bruce Potter's Newsletter at: http://swroc.coafes.umn.edu/SWMNPEST/swmnpest.htm

Co-Editors: Bill Hutchison, Department of Entomology, University of Minnesota, hutch002@tc.umn.edu
Jeanne Ciborowski, IPM Program, Minnesota Department of Agriculture, jeanne.ciborowski@state.mn.us
Cindy Tong, Department of Horticulture, University of Minnesota, ctong@extension.umn.edu
Production Editor: Suzanne Wold, Research Assistant, University of Minnesota, woldx018@tc.umn.edu

Disclaimer
Reference to products in this publication is not intended to be an endorsement to the exclusion of others which may have similar uses. Any person using products listed in this publication assumes full responsibility for their use in accordance with current directions of the manufacturer

Last Revised May 30, 2002.
The University, including the Minnesota Extension Service, is an equal opportunity educator and employer.©2002 Minnesota Extension Service, University of Minnesota. All rights reserved. Contact copyright@extension.umn.edu for information on reproduction or use of this material.