Georgia Updates Use Recommendations for Dicamba, Liberty in Cotton
June 10, 2020 Following the June 3 Ninth Circuit Court of Appeals ruling revoking labels for three dicamba products – XtendiMax, FeXapan and Engenia – and the subsequent EPA order allowing use of existing dicamba stocks through July 31, Georgia Extension Weed Specialist Stanley Culpepper has updated his recommendations for dicamba and Liberty use to help meet immediate weed control needs in the state.
For dicamba, Culpepper offers three scenarios for growers to consider:
Scenario One: Large pigweed with enough in-crop dicamba for two applications. Spray labeled Roundup + dicamba immediately, wait 7 to 10 days and then make a second application. Twelve days later, run the layby rig with either 1) Direx + MSMA + Crop Oil if grasses are not up, or 2) Roundup + Direx if grasses are up (add Envoke with layby if morningglory or nutsedge is a problem).
Scenario Two: Large pigweed with enough in-crop dicamba for one application. Spray labeled Roundup + dicamba immediately, wait 7 to 10 days and then make a Liberty tank mix application. Twelve days later, run the layby rig with either 1) Direx + MSMA + Crop Oil if grasses are not up, or 2) Roundup + Direx if grasses are up (add Envoke with layby if morningglory or nutsedge is a problem).
Scenario Three: Large pigweed with no dicamba available. Sequential Liberty applications will be the best approach, although less effective than either dicamba scenario.
Culpepper noted that teamwork between the Georgia Department of Agriculture and BASF allowed Georgia to obtain a new Liberty 24(c) state label that shortens intervals between sequential applications of glufosinate to help cotton growers improve control.
“Research has shown that understanding the time interval between sequential post applications is one of many critical components for an effective weed management system,” says Culpepper. “Obviously, one needs to spray Liberty when the biggest pigweed in the field is 3 inches for complete control, with a follow-up application when the next flush of pigweed reaches 3 inches. With the challenging weather during 2020, spraying all weeds at 3 inches or less may not be practical for some fields. Thus, when pigweed is too large to kill with the first application, then the second application timing is important.
A few critical points from the 24(c) label:
- Growers must have a copy of the 24(c) label in hand when making application
- Liberty may be applied twice over-the-top of glufosinate-tolerant cotton as long as there is at least a 5 day interval between applications
- Do not include tank mix partners when making two applications less than 10 days apart
- Do not apply more than 36 oz/A over the top of cotton per application
For resistance management purposes, Culpepper urges Georgia growers to make no more than two Liberty applications. Following the second Liberty application, growers can come back 10-12 days later with a layby directed application including conventional chemistry such as Diuron + MSMA + Crop Oil or Roundup + Diuron (add Envoke with layby if morningglory or nutsedge is an issue – and check carryover).
“In Georgia, we have all worked so hard to steward every pesticide, and we should collectively be proud,” says Culpepper. “However, this (dicamba ruling) is a wakeup call in several ways. First, we must work together even harder generating sound science to preempt this type of situation in the future. And second, it should be a clear wakeup call for those few growers who have downplayed the importance of using all pesticides wisely.”
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