Corn harvest will likely start toward the end of this month. As the corn dries down the next couple weeks expect a new flush of Palmer amaranth. Moreover, with all the rain the first week of August any thin corn stand areas will likely have a new heavy flush of Palmer amaranth. Though no one wants to spend more money with corn commodity price so low, it will pay off next spring to have less Palmer amaranth to mange in soybean or cotton. Good options to control this late flush of Palmer include tillage and the burndown herbicide Gramoxone (paraquat).
Please note if you elect to go with tillage that a disking will likely provide good control of smaller Palmer (<4”) but larger Palmer (>8”) will often re-root and grow back. Likewise, Gramoxone will provide consistent control of smaller Palmer but regrowth can happen with larger Plants.
Residual herbicides should be considered as well with so much growing season left. Fall applied residual products like Sharpen, Valor, Dual Magnum, metribuzin and simazine would all be good choices here, depending upon what crop is to be planted next spring.
Sharpen is probably one of the more versatile residual options as wheat can be planted anytime after the herbicide is applied. Sharpen can be used at rates up to 2 oz/A in the fall before wheat, corn, grain sorghum and soybean. Valor could work as well if corn harvest is early as there is a 30 day plant back to wheat after a Valor application.
Other residual options can work as well like Dual Magnum or metribuzin if the fields will go to crops other than wheat this fall.
Larry,
Trying to manage (control is folly) Palmer has been an expensive proposition in 2012. If the cost of every attempt to manage Palmer in any fashion is dutifully added to our overall input costs, it would blow Chuck D’s crop budgets out of the water. And now you are recommending a post-harvest spray for late emerging Palmer. I think your idea is a good one, but it also adds more expense to this year’s weed control budget.
It is the cost of managing resistant Palmer that has reached a crisis level. What row-crop farmers need from Extension personnel is a realistic, common sense plan to manage this weed with all current technology on the table. We cannot spend ourselves into oblivion trying to eliminate every new Palmer that comes up with every rain or irrigation. There are 20″ Palmer in the county road ditch at the end of my driveway right now. That ditch has been sprayed, mowed, etc. but they keep coming back.
Managing this weed while managing that cost is the real challenge.
Richard
Richard
Thanks for the comment and I agree. My biggest concern is not controlling late flushes in soybean or cotton but corn. We had alot of bad pigweed fields rotated to corn this year. I hate to see a huge flush of Palmer with a good 2 months of growing season yet produce a huge seed load that will make controlling this weed in cotton or soybean next year even more expensive. If we can minimize Palmer seed production this fall we may at least cut out one Liberty application next year which would be more expensive than a Gramoxone Plus residual program I mentioned. Moreover, it helps put less selection pressure on Liberty as well.
Thanks
Larry