Category Archives: Soybean

Weed Management Report Card 2022

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Picture 1. Palmer amaranth that escaped Warrant PRE fb/Engenia + Roundup + Outlook Post fb/Liberty + Roundup 2nd Post

Every fall we travel around the state and observe the overall success or failure of weed control in our row crops. From the Palmer amaranth standpoint a few too many fields look like a failure.  Particularly, from Gibson county across to Lauderdale county cotton and soybean fields ranged from clean fields to fields with more weeds than one would like (Picture 1) to completely grown up pigweed messes (Picture 2). Continue reading

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Soybean Looper Numbers Increasing

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I’ve received several calls about looper numbers increasing in soybeans across West Tennessee. Numbers range from 3 per 25 sweeps to 25 per 25 sweeps. Treatment is recommended when defoliation exceeds 20% from R1 to R6 or if looper numbers exceed 19 per 25 sweeps. It’s often suggested to ignore small worms (<1/2 inch) in these counts due to predators and entomopathogens taking a substantial toll on their survival.

Pyrethroid additions, at R3 fungicide timing, can exacerbate looper numbers and shouldn’t be included unless they are needed. This is one of the reasons I caution against including an automatic pyrethroid with fungicides at R3 and those applications won’t have any measurable impact on stink bug numbers when the beans hit R5. Loopers are one of the top pests encountered in late planted soybeans and are the most expensive to control. Further, I received word from my colleagues in Mississippi that low rates of diamides (1.2 fl oz/a Vantacor, 7.0 fl oz/a Besiege, 14.0 fl oz/a Prevathon) are providing unacceptable levels of control in large populations of loopers. This isn’t a surprise but take caution when utilizing diamides. Reports of diamide slippage on loopers has occurred for several years and more often than not, it occurs when low rates are utilized against high numbers (>1.5X threshold). Another product, Intrepid 2F (methoxyfenozide), has also had some control issues in Arkansas and Mississippi. Rates of 4.0 and 6.0 fl oz/a did not provide satisfactory control of loopers 7 days after application; however, Intrepid Edge (methoxyfenozide + spinetoram) performed very well. We have several insecticide options available at our disposal but if you’re facing large numbers, low rates of any product (especially the diamides) probably won’t cut it.

One final comment, don’t confuse soybean loopers with green cloverworms. Loopers have 2 pairs of prolegs cloverworms have 3 (see images below). Cloverworms are much easier to control than loopers and pyrethroids, as well as other insecticides, work well. Information on insecticide options for loopers can be found here:

Soybean Looper Larva
Soybean Looper Larva
Green Cloverworm Larva
Green Cloverworm Larva
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Reminder: Soybean Disease Field Day Sept. 7th

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Wondering what’s been making your soybeans sickly? Come to The University of Tennessee Soybean Disease Field Day, held Wednesday, Sept. 7th, at the Milan Research and Education Center. Registration will be from 8:30-9:00 AM with the tour beginning at 9 AM and concluding with a box lunch.  Preregistration is not required. Pesticide re-certification and CCA points will be available. Continue reading

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Insect Numbers Increasing in Soybeans

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Insect infestations have been generally mild in soybeans thus far, but I am starting to get more calls about stink bugs and a few other pests. As other crops mature, including early maturing soybean fields, late season insect populations often concentrate in the green islands of soybeans in the field. This may include corn earworm infestations in our latest maturing fields.

Stink Bugs are the topic of most calls at this time.  Here are a few points to consider.

  1. Populations often start building rapidly at about R5.  It really doesn’t matter if you already sprayed a few weeks ago when applying a fungicide. Infestations often continue to build up to and past R7.
  2. Treatment for stink bugs is recommended when you average 9 or more insects per 25 sweeps until R6 (full seed in the top of the plant). The only caveat to this is the redbanded stink bug which has a threshold of 4/25 sweeps. I highly doubt we will experience redbanded stink bug infestations this year or if we do, it will be in the southern most counties in very late beans.
  3. You should double this threshold (18/25 sweeps) in next 7-10 days after fields reach R6.
  4. Green stink bugs have composed the majority of stink bugs we’ve found thus far. Pyrethroid insecticides such as Brigade and other bifenthrin products, Karate/Warrior, Mustang Max provide good control of green stink bugs. I would be more inclined to use Orthene/Acephate if brown stink bugs are usually common.

I’ve also received a few calls about worms in beans. So far, soybean loopers haven’t shown up on a large scale and most fields have a mix of loopers, cloverworms and other assorted worms. With worms in beans, coverage is typically more important than insecticide rate. Corn earworms respond to lower rates of diamides (Vantacor, Elevest, Besiege) in soybeans than in cotton. Similarly, Intrepid Edge is effective for corn earworms in beans but not particularly effective in cotton. Green cloverworms and velvetbean caterpillars are susceptible to pyrethroids and will often be removed by applications for stink bugs or other insects.  Soybean loopers may require higher rates of diamides due to resistance issues.  Soybean looper populations migrate from South/Central America every year and resistance levels are hard to predict, control level/duration often decreases with lower rates of diamides.

Like our stink bug threshold, the defoliation threshold in soybean should be relaxed from 20% to 30-35% once fields reach R6. Making an insecticide application for defoliating pests once you are 7-10 days past R6 is not recommended. Don’t spray for defoliators if fields are beginning to turn color and naturally defoliate.


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Dicamba-Resistant Waterhemp Becoming a Real Issue in Middle Tennessee Counties Bordering Kentucky

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Picture 1. Montgomery County 2020: Waterhemp that escaped multiple applications of Engenia + Glyphosate

For the past several weeks we are getting reports of waterhemp escaping dicamba application/s from retailers and consultants scouting fields in Montgomery and Macon counties.  As one retailer so aptly described it today “combines have spread it and we are fighting it all over the county now”. Continue reading

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Bollworm/Budworm Moth Trap Catches (8/12)

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Weekly Moth Trap Data
Date: 8/12
Location Bollworm Tobacco Budworm
Hardeman (Bolivar) 2 1
Fayette (Whiteville) 3 0
Fayette (Somerville) 0 0
Shelby (Millington) 13 16
Tipton (Covington) 0 0
Tipton (North) 0 0
Lauderdale (Goldust) 53 14
Haywood (West) 3 0
Haywood (Brownsville) 1 0
Madison (WTREC) 23 0
Madison (North) 1 2
Crockett (Alamo) 0 1
Crockett (Maury City) 1 0
Dyer (Kings Rd) 13 3
Dyer (Newbern) 1 4
Lake (Ridgely) 3 35
Gibson (Kenton) 11 2
Gibson (Milan REC) 3 1
Carroll (Atwood) 29 3
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EPA Requests Comments on Organophosphate Cancellation Petition

The EPA is soliciting public comment on a petition from several organizations to cancel remaining organophosphate (OP’s) insecticide registrations. OP’s are widely utilized in Tennessee row crop agriculture and are critical components of IPM programs. Cancelling an important crop protection product would place increased pressure on a limited number of control options available to producers.  We are encouraging agricultural professionals to comment to the EPA on the impacts OP’s have on your production systems. If you need assistance with comments please contact your UT extension specialist. The link to comment is below. Deadline for comments is August 11, 2022.

Organophosphate registrations



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Bollworm/Budworm Moth Trap Catches (8/5)

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Weekly Moth Trap Data
Date: 8/5
Location Bollworm Tobacco Budworm
Hardeman (Bolivar) 1 1
Fayette (Whiteville) 10 0
Fayette (Somerville) 1 0
Shelby (Millington) 12 15
Tipton (Covington) 2 0
Tipton (North) 1 0
Lauderdale (Goldust) 40 20
Haywood (West) 6 0
Haywood (Brownsville) 0 0
Madison (WTREC) 50 2
Madison (North) 3 1
Crockett (Alamo) 0 0
Crockett (Maury City) 6 10
Dyer (Kings Rd) 35 1
Dyer (Newbern) 2 0
Lake (Ridgely) 19 15
Gibson (Kenton) 30 1
Gibson (Milan REC) 0 1
Carroll (Atwood) 23 2
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