I know this has been a frustrating planting season to say the least.  Replanting has been more the rule than the exception this spring.  There have been reports of fields that were first planted to corn then replanted to cotton and now will likely be replanted to soybean. With all the troubles planting and replanting this spring please do not forget to manage Palmer amaranth or you may have to replant yet again just to control the pigweed.  These June weather conditions are shaping up to be a perfect Palmer amaranth storm! 

I got the first of what I hope are not many calls on “how do I control 6” Palmer amaranth in my RR soybeans”.  Due to all this wet weather the pre applied herbicides are giving out quickly. Even the better residuals herbicides for Palmer amaranth like Prefix or Fierce are playing out in about 3 weeks. Palmer under these wet warm conditions can emerge and reach a height of 8” in just 13 days. Moreover, when it seems to rain 3 to 5” a week it makes it impossible to apply post emergence applications on Palmer amaranth timely.  Remember, there are no herbicides that will control a 3 to 4” Palmer amaranth, let alone an 8” Palmer, in Roundup Ready soybeans. The result of all this I fear is that we will see more grown up soybean fields then we have in the last couple of years.

We have yet to plant the large majority of the soybean crop.  It is critical that the field start out pigweed free!  Either use Gramoxone or tillage prior to planting soybeans.  A residual at this point must be used.  Then plan to overlay another residual about 7 to 10 days after planting.

In cotton most growers intend to keep Liberty in their weed control plan for cotton.  However, due to the Liberty price increase some are looking at cutting the rate from 32 or 29 ozs to 22 ozs/A.  Liberty at 22 ozs will typically control Palmer that is 2 to 3” tall.  However, if they are taller than that go with the higher Liberty rates.  Also, time of day can make a big difference on how effective Liberty is on Palmer amaranth.  Liberty applications between 9:00 a.m. to dark have been the most effective time to treat Palmer with Liberty.  Night applications or applications made just after sunrise have provided inconsistent Palmer control regardless of rate.