Rely® 280 Herbicide Available for Use in California Avocado Groves

The California Department of Pesticide Regulation has approved the herbicide Rely® 280 (glufosinate-ammonium) for use in avocado groves in California. Rely® 280 is a post-emergence broad-spectrum herbicide for use against broadleaf and grassy weeds. Glufosinate-ammonium is an excellent alternative to glyphosate, especially for those weeds that have developed glyphosate resistance. 

The California Avocado Commission provided funding for Dr. Peggy Mauk, extension professor for subtropical horticulture at the University of California-Riverside, to conduct efficacy trials with glufosinate-ammonium and the IR-4 program provided funding for the required phytotoxicity (crop safety) trials. “Glufosinate-ammonium is an effective broad-spectrum herbicide,” said Mauk. “The weed that is the biggest problem here in Riverside is mare’s tail or hairy fleabane (Erigeron bonariensis). Glufosinate will kill it depending on the application timing and size of the plants. Treating for weeds is also going to be seasonal…the spring is usually worse because spring rains bring a lot of weeds, especially this past year.”

Currently, growers must have a copy of the DPR approved supplemental label in their possession when using Rely® 280. The DPR-approved label has a stamp on it with the wording "LABELING ACCEPTABLE State of California Department of Pesticide Regulation Pestcide Registration" and can be downloaded from the link in the right hand navigation. This supplemental label expires on December 1, 2025, and BASF, Rely® 280's manufacturer, anticipates that all old product will be used by that date and new product with avocado listed on the package label will be fully in the supply chain by that date.  

Dr. Mauk’s phytotoxicity trials found minimal damage, assuming sound application practices are followed. “Spray applications should not be made when there is a breeze,” Mauk emphasized. “If the wind carries the herbicide onto the plants, there can be some leaf discoloration. The discoloration appears as occasional purple spots on the leaves. There is not widespread damage. We also never saw any discoloration on the avocado fruit.”

General questions about this registration can be directed to CAC's Research Director Dr. Tim Spann at [email protected] or 423-609-3451. For specific questions regarding the use of Rely® 280 growers should contact their Pest Control Advisor.