Cotton Weed Control
I have had a number of similar questions recently concerning burndown for no-till or strip-till cotton. Letís start with Valor; a lot of Valor is being used and there is apparently some confusion about waiting intervals between application and planting. The waiting interval basically depends upon type of tillage and when that tillage occurs.
|Conventional tillage, including stale seed beds||30 days and 1 inch rainfall between application and planting.|
|No-till (without strip-tillage)||21 days and 1 inch rainfall between application of 2 oz and planting. Can reduce to 14 days for 1 oz.|
|Strip-till before application||21 days and 1 inch rainfall between application and planting.|
|Strip-till after application||14 days between application and planting.|
I understand that Valor is in short supply. Several people have asked about Direx for a residual in the preplant burndown. The Direx (and other brands) label says the product can be applied 15 to 150 days ahead of planting. It also allows application behind the planter. I see no logic for not allowing application during the 14-day interval prior to planting. There are soil-type limitations on the label. Basically the label says to not use this product on sands or loamy sands or any soil with less than 1% organic matter. In limited NC research, we have not seen problems with Direx in the preplant burndown on any soil, but I would feel more comfortable saying that if we had more data. A word of caution: a cotton plant canít tell the difference between Direx and Cotoran. If one uses Direx in burndown, it would be wise to avoid Cotoran behind the planter.
Waiting intervals between 2,4-D or dicamba in burndown and planting: Few growers in NC use dicamba for burndown. The Clarity label (dicamba) specifies a 21-day waiting interval plus 1 inch of rainfall between application and planting. NC research suggests we do not want to cheat too much on that interval.
2,4-D labels specify a 30-day interval between application and cotton planting. We should always encourage growers to follow label recommendations. But, research suggests we can cheat on the waiting interval between 2,4-D application and planting. I refer you to an article we published in Journal of Cotton Science in 2004. You can find that article at http://www.cotton.org/journal/2004-08/3/upload/jcs08-213.pdf. We use metric units in the article, but 530 and 1060 g/ha is equivalent to 1 and 2 pt/acre 2,4-D, respectively. In that article, you will see we had no problems with cotton planted two weeks after application.
Will strip-tillage after 2,4-D or dicamba application affect the chances of injury to cotton, or allow one to plant sooner? Probably not.