The call of the week has one theme “PIGWEED”.  Many folks are noticing that herbicides like Cotoran and Caparol have played out and now they have Palmer amaranth up in their cotton. In some late May/early June planted cotton that has not had rain, the Pre herbicide was not activated. It appears that much of the Palmer emerging in these fields was not controlled with glyphosate applied last week and early this week. The folks with their fields planted to WideStrike cotton are trying to weigh the choice of whether to spray Ignite and what to tankmix with it? 

Most folks approach spraying Ignite on WideStrike with caution and they should.  Every time Ignite is applied to WideStrike cotton it will injure it. However, in research from GA, TN, NC, MS, AR and LA that injury has rarely translated into yield loss.  The one time it did was on heavily thrips injured cotton. Of course, we have a lot of cotton that is stressed by thrips so the decision comes down to weighing the potential injury from Ignite to the yield loss from Palmer amaranth competition.  In a study Scott Stewart conducted last spring cotton without an insecticide seed treatment was allowed to be injured by thrips and then sprayed with Ignite and Ignite tankmixed with three different insecticides on 2 leaf cotton.  In this test he lost about 11% of the yield when comparing the Ignite application alone to Sequence on the thrips stressed cotton. Recent research from Georgia shows that just one Palmer/sq yard will reduce cotton yield by 50%. So it comes down to getting eyes on the field to determine the extent of the Palmer infestation. If it is just a couple spots of Palmer and maybe a few scattered then spray glyphosate plus a residual and chop or otherwise destroy the pigweed in those areas. If the Palmer infestation is much more robust then the down side of yield loss, that may or may not happen, with Ignite on WideStrike cotton will be more than offset by the 100% guarantee of extensive yield loss from Palmer amaranth competition. 

The next question from growers is should they tankmix a residual herbicide, AMS or insecticide in with the Ignite on WideStrike cotton?  I would be very cautious adding a Dual Magnum in with Ignite on Widestrike cotton particularly if it has been stressed by thrips.  A better approach is to wait a few days and spray a residual herbicide then.  I would also not add any AMS.  It will likely not improve weed control and very likely increase cotton injury. The insecticide is a different story.  We have not seen acephate increase injury of Ignite on Widestrike cotton and with the thrips pressure in many fields this year it probably is warranted. There is some Liberty Link cotton, which has much better Ignite tolerance than WideStrike cotton, scattered around Tennessee this year and the decisions on managing GR Palmer is easier.  I would spray the cotton as quickly as possible with Ignite and tankmix in something like Dual Magnum for residual control and insecticide for thrips if needed. 

I have had several calls where folks have sprayed Ignite on their cotton last week and been surprised that some of the Palmer that is 4” or more tall is starting to grow back.  Last year these same folks were able to control 4 to 6” Palmer with 29 ozs of Ignite.  Last year to me was more the exception than the rule.  Most years, including this year, in our research 29 ozs of Ignite on 4 to 6” Palmer may only provide about 60% control.  It typically takes a second Ignite application applied about 7 to 10 days after the first application to control the regrowth.