Category Archives: Weeds

Palmer amaranth Escaping Auxin Herbicides as well as Follow Up Liberty Application

Picture 1. Palmer amaranth escapes after Enlist One + glyphosate followed by Liberty. Picture taken 17 days after Liberty application.

We have visited fields where growers have found that Palmer amaranth that escaped an auxin herbicide (Engenia, XtendiMax, Enlist One) application also escaped follow-up glufosinate (Liberty) application (Pictures 1 and 2). Auxin herbicide-resistant Palmer amaranth was documented in Tennessee last year.  As such, it was not a surprise to find dicamba or 2,4-D fail to control pigweed. Glufosinate-resistant Palmer amaranth was documented in Arkansas last year.  We have not found glufosinate-resistant Palmer amaranth on the Tennessee side of the river.  However, the reports from these fields has us concerned the glufosinate-resistant biotype has indeed crossed the river. Part of the reason for the concern is that we had research fairly close to these suspect fields that showed similar poor Palmer control with dicamba or 2,4-D followed by glufosinate. Continue reading

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Manage Large Palmer amaranth Escapes

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Picture 1. Palmer amaranth escapes from Engenia + glyphosate. Picture taken 30 days after application.

We have visited fields where growers assumed their Engenia or XtendiMax + glyphosate had controlled Palmer amaranth only to find that many had escaped and are now quite large (Picture 1). The question is what are some approaches to manage these escapes? Continue reading

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Management of Auxin-Herbicide Resistant Palmer Amaranth

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In fields where dicamba and 2,4-D are no longer effectively controlling Palmer amaranth what are some options to help manage this weed?  We conducted research at several locations this year trying to answer this question.

Picture 1. Palmer amaranth escapes from dicamba + glyphosate on 4″ Palmer followed by dicamba + glyphosate 7 days later.  Picture taken 21 days after last application

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Dicamba and 2,4-D: No longer “Palmer amaranth Herbicides” in Some Fields

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Picture 1. Palmer amaranth escapes 18 days after 12.8 ozs Engenia+ 32 ozs glyphosate. A farmer’s field, Lauderdale county, TN

For the past week we have been getting reports along with a good many pictures of Palmer amaranth escaping dicamba application/s from retailers and consultants scouting fields (Picture 1 and 2).  As one retailer so aptly described it today “there are spots in fields where the lack of Palmer control is frightening”. Continue reading

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More Reports of Barnyardgrass/Junglerice Escaping Glyphosate and/or Clethodim

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There have been several reports last week of multiple glyphosate and/or clethodim applications not controlling barnyardgrass or junglerice.  We really do not know the precise reasons for the lack of control in any given field but based on previous research and past experience there are three likely causes. Continue reading

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Palmer amaranth Control Options now that June 30 Dicamba Cut-Off in Soybean has Arrived

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It is July 1, 2021 so the June 30 cut-off to spray dicamba over Xtend soybean has passed.   The questions of the week have been once July has arrived what alternatives are there to control Palmer amaranth in soybean? Continue reading

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Glyphosate-Resistant Johnsongrass can Foster an Old Corn Disease

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Stunted corn near Johnsongrass

Two old and now “new” again corn viral diseases Maize Dwarf Mosaic (MDM) and Maize Chlorotic Dwarf (MCDV) have been causing severe stunting of corn in a few fields in southwest Tennessee. With the slowly increasing spread of glyphosate-resistant (GR) Johnsongrass it was only a matter of time before these two diseases would once again become an issue in corn. Continue reading

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Zidua Impregnated on Fertilizer Applications in Cotton

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There are some who have or soon will apply Zidua (pyroxasulfone) via impregnated fertilizer in cotton. My understanding is that this has been done successfully in Texas in years past.  Along with those applications we have applied some in research as well a few days ago.  One would expect no cotton injury applied via fertilizer to dry foliage. Indeed, that was the case in our trials. Continue reading

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