Stinger Herbicide Now Registered for NC Strawberries

By David Monks, NCSU Dept. of Horticulture. Edited from an article in The Strawberry Grower, September 2003.

In late August, the herbicide Stinger was labeled for use by North Carolina strawberry growers. This has been a long process, but Stinger will be a valuable tool for our growers.

Stinger was developed by and is marketed by Dow AgroSciences for a number of crops, including strawberries. It is registered for the control of the following weeds: Jerusalem artichoke, clovers, common cocklebur, curly dock, dandelion, groundsel, jimsonweed, prickly lettuce, nightshade, common ragweed, giant ragweed, smartweed (suppression), red sorrel, sowthistle (suppression), sunflower, bull thistle (suppression), Canada thistle (suppression), and vetch.

Growers will need to sign a waiver of liability for the use of Stinger in strawberries in North Carolina before they can obtain a label and use the herbicide. Use of waivers like this is increasingly common in high value crops and with some herbicides. Dow AgroSciences would only agree to bring Stinger to market if there was a waiver to reduce their liability. The waiver program will be managed through the NC Strawberry Association. Growers must sign the waiver included in this newsletter, or request a waiver from the NC Strawberry Association, sign the waiver, and then return it to the NC Strawberry Association office. NCSA’s Executive Secretary will then provide a copy of the label to you. You will also be able to sign the waiver at the Southeast Strawberry Expo and pick up a label there. The waiver and label will NOT be available from other sources, such as your farm supply dealer selling the product.

The critical information on Stinger use is provided on the Stinger label. Be sure to read the label prior to use.

Currently, Stinger is registered for strawberries in a few other states, including Ohio and New Jersey, but not the ones surrounding North Carolina.

Stinger been evaluated in our strawberry research since the early 1990s to support a possible registration in strawberries. One graduate student, Greg McMurray, spent several years researching the product in strawberries. Food crop registrations for Stinger have been developed through the IR-4 program, a program that is responsible for assisting with establishing tolerances of pesticides for minor use crops. This program establishes an EPA-approved protocol for field residue trials. Data is collected and then submitted to EPA for the purpose of establishing a tolerance. Once a tolerance is established, a label can be written.

In our Stinger research, several field sites were established. The strawberry plants were sprayed with Stinger, and as the crop matured, fruit were harvested and then trucked to a laboratory where residue of clopyralid, the active ingredient in Stinger, was evaluated. We presented our research results to a committee on campus responsible for making recommendations to the NC Department of Agriculture and Consumer Sciences with regard to the need of a state label for Stinger, and then NCDA&CS worked with Dow Agro-Sciences to develop the label for NC. More recently I assisted the company with writing and revising the Stinger label so that it suited NC production.

Our initial research with Stinger in strawberry was on Danny McLawhorn’s farm in Pitt County, NC. Our results at 1/3 pint Stinger per acre in plasticulture strawberries were 90% vetch control at four weeks after spraying, increasing to 100% at eight weeks after spraying. It did an excellent job not only controlling vetch growing from the hole in the plastic near the crop, but it also controlled the rest of the weed growing under the plastic. It was safe to the crop. Since then, we have conducted many trials, including a variety strawberry trial, each time demonstrating effective weed control.

Stinger is registered in plasticulture strawberries at 1/3 to 1/2 pint Stinger per acre. The rate can be increased to 2/3 pint Stinger per acre in row middles. Stinger is active only on specific weed species, thus it is not uncommon to observe species of weeds that are not affected by Stinger. Also, there are no grasses listed on the Stinger label; thus attempts to control specific broadleaf weeds growing in middles where ryegrass is growing should not affect ryegrass.

In matted row strawberry production, 1/3 pint per acre Stinger can be applied in spring, and/or 1/3 to 2/3 pints per acre post-harvest. Stinger can not be applied within 30 days of strawberry harvest.

One area of research this next year will be crop rotation, where other crops will be planted on the plastic following use of Stinger on strawberries to identify crops which can be safely planted following Stinger use. Our concern is that certain crops may be sensitive to Stinger.