All posts by Larry Steckel, Extension Weed Specialist

Multiple-Herbicide Resistant Waterhemp in Tennessee

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Waterhemp that escaped multiple applications of Engenia + Glyphosate

Last year we reported on waterhemp in Montgomery and Macon counties that was resistant to dicamba.  We came to this conclusion from both research we conducted in the fields and the confirmation of those results by greenhouse research. The greenhouse research was conducted at Purdue University by my colleague Dr. Bill Johnson and his graduate student Claudia Bland. Continue reading


Fall Application Ryegrass Control

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Corn in a ryegrass field

Ryegrass has become a serous weed issue in some fields that past couple of years.  A major reason for this is that much of it is now glyphosate-resistant.  Even if clethodim is used rather than glyphosate often it is applied on ryegrass sometime in late March through April when the grass is too well established to provide consistent control. Continue reading


EPA Herbicide Strategy Frame Work Will Impact All Pesticide Applications in Tennessee

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In response to losing lawsuits on lack of action on the endangered species, the EPA proposed a draft strategy aimed at guarding federally endangered species against potential negative impacts of herbicide applications. They describe the strategy as a mix of population-level protections for over 900 listed species and designated critical habitats with a range of mitigation measures. What the EPA is proposing to do will eventually impact every pesticide application in Tennessee.

This is a very complicated topic.  I found the two WarAgainstWeeds podcasts helpful in trying to understand the “why, where and how” of EPAs strategy.

If you would like to comment to EPA on this plan (I would urge you to comment!), here is a link: Write a Comment


A Step Back on Palmer Amaranth Control

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Picture 1. Palmer Amaranth Escapes in Xtend Soybean

Driving across West Tennessee last week it is very apparent we have taken a step backward on Palmer amaranth control.  Many fields that looked clean from the road in late July are now showing large Palmer amaranth escapes. Upon closer inspection the pigweed escapes are at least partially affected by the dicamba applications which resulted in them staying hidden from the road until the last couple of weeks. Continue reading


Best Time to Control Perennial Vines is Now

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Burcucumber over growing corn

Practically every September some growers are dismayed at the vine infestations present at corn harvest.  Often, these weed infestations emerged after PRE applied or early POST applied herbicides had played out.  They grew very little until August and as the corn dried down and light became more available those established weeds started rapidly growing.

The vines in question are often perennial in growth habit like honeyvine milkweed, redvine, hedge bindweed and burcucumber.  There is really no in-crop option that will provide good perennial vine control.  The best one can achieve with an in-crop application is enough vine suppression to minimize harvest issues.

Perennial vines are best controlled with herbicide applications after harvest.  The most consistent tactic is to allow the vines to grow back for a week or so after harvest and then apply dicamba and/or 2,4-D. Tank mixing in glyphosate can also increase vine control. For best results go with rates at the higher end of the labels. Continue reading


Ryegrass and Poa Management in Wheat

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The two best fall-applied options for ryegrass and poa in wheat are Anthem Flex and Zidua.  Pyroxasulfone is providing the grass control in both these herbicides.   Anthem Flex can be applied as a true PRE right behind the press wheel.  Keep in mind there is some chance of wheat injury from this new use pattern if a rain occurs shortly after planting.  As such, if rain is in the forecast wait and apply it later as a delayed PRE or early POST. Continue reading


When Dicamba Fails: Success and Failure

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Picutre 1. Dicamba pigweed escapes cleaned up in field with follow up Liberty application and a hooded diuron +MSMA application as well as cultivation

I have had the opportunity to visit fields where dicamba application/s failed to control Palmer amaranth and observe the success and failure of follow-up weed control tactics. On the positive side, where more timely and diverse weed control tactics were employed Palmer amaranth control was often a success.  In a couple of cases, timely Liberty applications on Palmer amaranth escapes often provided 70 to 80% control.  Follow-up hooded applications followed by cultivation increased Palmer control in these fields to greater than 95% (Picture 1). Continue reading


Control of Volunteer XtendFlex Soybean in XtendFlex Cotton.

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Picture 1. XtendFlex soybean infesting Xtendflex cotton.

A recent new “weed” issue in XtendFlex cotton is volunteer XtendFlex soybean (Picture 1). Recent research has shown that Envoke at 0.125 to 0.15 ozs/acre provides very good control as soon as 7 days after application (Picture 2). Continue reading