In The Field with Randy

Burndown

March is here and it’s time to get to the field. It’s been a wet February and about the only field work has been done with an airplane. It’s time to think about burndown herbicide programs if you haven’t started one already. Most are using burndown herbicide programs in one form or another. Burndown herbicide programs are used to keep fields clean where stale seedbed or no-till systems are going to be planted with no further tillage. They are also often used to keep the weed situation manageable which allows the fields to warm up and dry up more quickly in situations where tillage is planning on being used.

Roundup or Gramoxone are typically the base herbicide for most burndown applications. In general, I recommend Roundup before pigweeds start emerging and Gramoxone after. Depending on the weeds present and plantback intervals to other crops, I typically recommend tank mixing other herbicides such as 2,4-D, FirstShot, or Sharpen with the Roundup to broaden the spectrum of control on weeds that Roundup is weak on and for control of Roundup-resistant weeds.

If you’re considering Gramoxone, look at using a PSII inhibiting herbicide in a tank mix with Gramoxone. PSII inhibiting herbicides help the Gramoxone get into the plant better. Gramoxone is an outstanding contact herbicide but doesn’t translocate into the plant very well itself. For that reason, control may be lacking on some weeds because of that failure to translocate into the weed plant. The addition of the PSII inhibitor herbicides (metribuzin before soybeans, atrazine or metribuzin before corn or milo, or diuron before cotton) help the Gramoxone get into the plant and therefore raise the level of control. If you look at the ratings in the MP-44, many of the weed ratings from Gramoxone are increased 1 or 2 points with the addition of the PSII. There is not a PSII available to use in front of rice.

Another burndown situation becoming more common every year is ryegrass. There was some use of preemergence herbicides last fall to keep ryegrass from emerging and that is what I recommend especially where we know we have a problem. Dual, Zidua, or Anthem Flex can be used if corn, grain sorghum, or soybeans are going to be planted the following spring. Boundary can only be used if soybeans are going to be planted the following spring. Command got a label last fall to be used if rice is going to be planted the following spring. These herbicides should typically be applied in late October/early November.

In burndown situations in late winter/early spring, clethodim (Select and generic Select formulations such as

Section Three) can be used prior to jointing of the ryegrass. After jointing, we need to switch to Gramoxone or preferably Gramoxone plus a PSII if rice is not the crop to be planted. It may take 2 applications to get adequate control.

A residual herbicide such as Valor should be considered to keep fields clean after a burndown. Remember there is a 30 day plantback to everything except soybeans and peanuts when using Valor.

Always consider plantback intervals with any of these herbicides with soil activity. For 2,4-D, the plantback is 28 days for cotton, 21 days for rice, 14 days for soybeans, and 7 days for corn and grain sorghum. For FirstShot, the plantback is 14 days for corn, grain sorghum, and cotton. It is 7 days for soybeans and 0 days for rice. With Sharpen, there could be concern for soybeans planted on extremely sandy soils, and there is a 3 month plantback to cotton and 5 months to peanuts. Don’t forget that there is a 30 day plantback for rice, corn, and grain sorghum when following a clethodim application.

For more information, feel free to contact me through Farmers Supply Association at 870-318-0739 (cell) or by e-mail at randychlapecka@gmail.com N