Lack of PRE herbicides making weed control difficult

Lack of PRE herbicides making weed control difficult

Late planting in 2014. Suggestions for early-season herbicide use. Liberty Link technology explored.

A few weeks ago, the wind blew for about seven days. Everywhere I drove drills and planters were running like crazy.

I cannot blame anyone this year for planting while the planting was good. My crew is starting to go stir-crazy because conditions have not been right for us to do much of anything at my locations. Hopefully, by the time this article comes out we will have something done -- but between rain and wind it just has not happened yet.

Upon seeing all those planters and no sprayers running I knew things were about to get tough, both in rice and soybean.

I think I can eventually clean up larger grass in rice. Newpath plus NIS will, or has become, Newpath plus Facet or RiceStar or a propanil product, and we can hit it again.

Soybean is a different situation though. Without a PRE, weed control in Roundup Ready soybean becomes very problematic when pigweeds are involved.

The biggest problem we face in Arkansas is that our pigweed has a marginal tolerance to the PPO herbicides. I have seen data from other states, like Mississippi, showing pretty good control of pigweed with POST applied products like Blazer and Cobra. We do okay in some areas with these products but in other areas, including my research sites, they just do not perform as well as Flexstar (fomesafen). Tennessee and the Missouri Bootheel seem to be more like Arkansas.

Recommendations

So, when I get a call that no PRE was used, beans are just emerging and the farmer has 0.5- to 1-inch pigweeds, I am not sure what to do. The best treatment is Flexstar GT or Prefix, anything with fomesafen. But, if you spray that this early, what are you going to use for your second shot? And you will need a second shot.

So, this year, I have been recommending a shot of Blazer or Cobra very early POST when pigweeds are in the “pink” stage -- less than 1-inch tall -- maybe with a tank mix with Dual or Zidua and saving the Flexstar component for the last application to 2- to 3-inch pigweed.

However, there does not seem to be a best thing to do when residuals fail or are not put out in Roundup Ready. Many growers are taking advantage of the Roundup Rewards program and I applaud Monsanto for including competitors’ products in this program. But when that first shot fails we are finding ourselves in trouble.

It really makes me wonder why more growers do not adopt the Liberty Link technology. You have all the same tools as in a Roundup Ready soybean plus two POST shots of Liberty.

Perhaps if Bayer CropScience offered a Liberty Link Rewards program more of these heavy pigweed fields would get planted to Liberty Link. I feel that the University of Arkansas has done all we can to promote this technology without sounding biased. But it just makes sense to switch technologies up on some of these acres with so many challenges involved in staying in Roundup Ready. 

I do not accept yield as a valid excuse. We have multiple years of data on Liberty Link varieties that show good yields that are comparable to Roundup Ready varieties. I do understand the cost is higher with Liberty Link. But one thing that that can easily get overlooked in all this is the effect that just one large pigweed can have on yield.

The Liberty system is not perfect. I still recommend the use of a pre with Liberty and it is weaker on grass. But the bottom line is I just do not get the same desperate calls on Liberty fields as I do on Roundup Ready.

In addition, we are almost totally relying on PPO herbicides like Valor, Blazer, Cobra, Sharpen and Flexstar to grow Roundup Ready. In other states, resistance to the PPO chemistry in pigweed and tall waterhemp has already been reported. With differential tolerance and resistance already showing up how long before this chemistry stops working?

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