Category Archives: Insects

Cutworms in Seedling Corn

I’ve received a few calls in the past couple days on cutworms appearing in seedling corn. Below are some take home points on cutworms:

Cutworm in Corn
  1. You probably do not need to worry about cutworms if you have kept a weed free seed bed for 2-3 weeks prior to planting, and this is especially true if using some of the Bt corn technologies (see below). However, the weather this year has not generally allowed for burndown applications made 3-4 weeks before planting.
  2. Consider making an insecticide application near planting time. Relatively low rates of pyrethroid insecticides are typically effective for cutworm control. I do not recommend including an insecticide with herbicide applications that are made more than a couple weeks in advance of planting. Tank mixing an insecticide with an early burndown application may not be that effective. Cutworms you kill would have probably ‘cycled out’ before you planted. And because you cannot expect much residual control, there is the possibility of re-infestation between application and planting. The best time to make this application is within a few days before or after planting.
  3. Using Capture LFR or other in-furrow pyrethroid insecticide as an in-furrow spray can add some protection against insect pests not completely controlled by seed treatments (e.g., cutworms and sugarcane beetles). I would prefer a T-banded type application where some of the product is applied to the “shoulders” of the seed furrow. This should improve control of cutworms compared with an application where 100% of the product is applied in-furrow. However, in-furrow applications appear to provide adequate control of cutworms in most circumstances.
  4. No insecticide seed treatments should be expected to provide substantial control of cutworms. However, I have seen Poncho 1250 kill small cutworms in the past, don’t bet the farm on this though. Some Pioneer corn seed now includes a base treatment of Lumivia (chlorantraniliprole). This product should provide at least some control cutworm, but data is limited.
  5. Although Bt corn and cotton traits provide some protection against cutworms, planting into fields that are heavily infested can be risky. Bt corn traits such as Leptra, VT2 Pro, SmartStax, Viptera, ad nTrecepta corn can reduce cutworm injury. Vip corn (Leptra, Trecepta, Viptera) will provide the best protection from a Bt stand point. However, large larvae are much less susceptible to Bt toxins.
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August 31 Bollworm/Budworm Catches for West TN

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Location CEW TBW
Hardeman (Bolivar) 2 0
Fayette (Whiteville) 3 0
Fayette (Somerville) 12 0
Shelby (Millington) 4 0
Tipton (Covington) 3 0
Tipton (North) 3 0
Lauderdale (Golddust) 8 0
Haywood(West) 9 0
Haywood (Brownsville) 15 1
Madison (WTREC) 9 0
Madison (North) 0 0
Crockett (Alamo) 0 0
Crockett (Friendship) 2 0
Dyer (King Rd) 12 0
Dyer (Dyersburg) 1 0
Lake (Ridgely) 12 0
Gibson (Trenton) 30 0
Gibson (Milan Rec) 0 0
Carroll (Coleman Farm) 8 0


Numbers are consistently going down across West TN and this is the last week for trap catches.

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Corn Earworms Showing Up in Soybeans

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I’ve received a few calls this week on corn earworms (bollworm/podworm) showing up in fields across Tennessee.  UT’s threshold for earworms, in beans, is based on sweep net sampling, crop value and control costs. The table below outlines the threshold based on the above factors.

Corn Earworm Threshold in Soybeans
Corn Earworm Threshold in Soybeans

Crop value is on the left-hand side, control costs are the 3rd row from the top and numbers beneath control costs are earworm numbers per 25 sweeps. The spot price of beans for (8/31) is $13.75 and control costs can vary from $10 to $16, depending on product choice, so the threshold in 25 sweeps would be 5 to 6 earworms per 25 sweeps. As crop price and control cost changes so does the number of earworms in our threshold.

Moths are typically attracted to later planted, more open canopy fields. However, earworms can be found in any stage beans. Insecticide choice depends on a few factors. If earworms are at or near threshold, acephate (0.75 lb/a) plus a pyrethroid is a cheaper option that provides acceptable control. This option runs the risk of flaring other pests (loopers, mites) and fields need to be rechecked 4-5 days after application to makes sure adequate control was achieved. If worms are above threshold safer choices would be Vantacor (1.2 fl oz), Elevest (5.0 fl oz), Besiege (7.0 fl oz), Intrepid Edge (4.0 fl oz) or Blackhawk (2.0 oz). The diamides (Vantacor, Besiege, Elevest) will have the longest residual control but many earworm issues in TN beans are solved after one application.

Another, more nonconvention option is Heligen (1.0 – 1.5 fl oz). Heligen is earworm specific and doesn’t have a fit on every acre. Applications should be initiated on small larvae at half a threshold (typically 2 – 4 larvae in 25 sweeps). Heligen is a virus that spreads throughout the field via infected larvae and requires some patience and knowledge of infection symptomology.

One final note, this product should almost be looked at as a preventative not a curative product. However, worms have to be in the field for the virus to infect the target and replicate causing an epizootic.  Large populations of earworms, at or above threshold, need a conventional insecticide.

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August 24 Bollworm/Budworm Catches for West TN

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Location CEW TBW
Hardeman (Bolivar) 19 0
Fayette (Whiteville) 23 0
Fayette (Somerville) 24 2
Shelby (Millington) 20 0
Tipton (Covington) 2 1
Tipton (North) 11 0
Lauderdale (Golddust) 32 0
Haywood(West) 18 0
Haywood (Brownsville) 33 0
Madison (WTREC) 33 0
Madison (North) 18 0
Crockett (Alamo) 0 1
Crockett (Friendship) 26 0
Dyer (King Rd) 28 0
Dyer (Dyersburg) 33 0
Lake (Ridgely) 39 0
Gibson (Trenton) 86 0
Gibson (Milan Rec) 1 0
Carroll (Coleman Farm) 17 0
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Bollworm Egg Lay Increasing in Cotton

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Bollworm egg lay across West TN is rapidly increasing. Our trap catches across the survey area are steadily increasing and I’ve started receiving several calls about large numbers of eggs . Fortunately, the vast majority of our cotton is Widestrike 3 (WS3) or Bollgard 3 (BG3). To date, I’ve had no reports of slippage through any three gene cotton in Tennessee. Going forward, our threshold for foliar applications targeting bollworms occurs when a combination of square and boll sampling shows 6 percent or more injury (e.g., 3 percent square injury and 3 percent boll injury, 4 percent square injury and 2 percent boll injury, etc.) and/or 4 or more larvae are present per 100 plants. Treatments based on egg lay is not recommended in 3 gene cottons. My colleague at Mississippi State, Dr. Tyler Towles, summarized our regional data (Fig. 1) demonstrating no economic benefit to making a diamide application to 3 gene cottons. Unless you’re at threshold, save the money on the diamide spray in 3 gene cotton.

One final note, as we are nearing the end of the 2023 growing season below are insect termination timings based on DD60s.

  • Tarnished Plant Bugs: NAWF 5 + 300 DD60s
  • Bollworms: NAWF 5 + 350-400 DD60s
  • Spider Mites: NAWF 5 + 350 DD60s
  • Stinkbugs: NAWF 5 + 400-450 DD60s
  • Fall Armyworms: NAWF 5 + 400-450 DD60s
Fig 1. Diamide Sprays by Bt Technology
Fig 1. Diamide Sprays by Bt Technology
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August 17 Bollworm/Budworm Catches for West TN

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Location CEW TBW
Hardeman (Bolivar) 6 0
Fayette (Whiteville) 29 0
Fayette (Somerville) 26 0
Shelby (Millington) 42 0
Tipton (Covington) 2 0
Tipton (North) 20 0
Lauderdale (Golddust) 35 0
Haywood(West) 8 1
Haywood (Brownsville) 67 0
Madison (WTREC) 41 1
Madison (North) 35 0
Crockett (Alamo) 1 1
Crockett (Friendship) 51 0
Dyer (King Rd) 48 1
Dyer (Dyersburg) 61 0
Lake (Ridgely) 35 2
Gibson (Trenton) 98 0
Gibson (Milan Rec) 4 0
Carroll (Coleman Farm) 15 2
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August 10 Bollworm/Budworm Catches for West TN

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Location CEW TBW
Hardeman (Bolivar) 3 0
Fayette (Whiteville) 31 1
Fayette (Somerville) 12 0
Shelby (Millington) 36 0
Tipton (Covington) 4 0
Tipton (North) 15 0
Lauderdale (Golddust) 17 0
Haywood(West) 21 1
Haywood (Brownsville) 26 0
Madison (WTREC) 48 3
Madison (North) 18 0
Crockett (Alamo) 1 2
Crockett (Friendship) 27 0
Dyer (King Rd) 44 1
Dyer (Dyersburg) 45 1
Lake (Ridgely) 20 2
Gibson (Trenton)
Gibson (Milan Rec) 2 5
Carroll (Coleman Farm) 20 0

Due to the excess rainfall we experienced over the past week, we weren’t able to reach our Trenton location. If moth numbers are exceedingly high, I’ll update the post and send out those numbers tomorrow.

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August Insect Situation

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I’ve received several calls over the past few days about large numbers of immature plant bugs being found 7-10 days after insecticide applications. Corn is quickly drying down, pigweed and other wild hosts have flowered and cotton is at peak bloom in several areas. This makes cotton an ideal host for plant bugs and in some instances the only host. Our top tier products (Transform, Orthene, Diamond, Orthene + pyrethroid) are still controlling plant bugs well and are about the only options we have in August.

Diamond is an insect growth regulator (IGR) that’s primary activity is on plant bug nymphs. Generally speaking, smaller nymphs (1st-2nd) are easier to control with IGRs than larger nymphs. Fields with a high population of larger nymphs (3rd-5th) will see slower control ofplant bugs than fields with predominately small nymphs. Diamond’s efficacy isn’t usually apparent until 10-14 days post treatment. Checking behind Diamond 6 to 7 days post may not give you an accurate representation of what’s happening in your field. However, if nymph numbers, especially small nymphs, are increasing by day 10 retreatment may be justified. Getting the best control with Diamond requires knowing the size of your predominate plant bug nymphs are and a little luck on the timing. Also, Transform and Diamond don’t have activity on stink bugs, the addition of a pyrethoid or organophosphate to oversprays will take care of stink bugs in cotton

A quick note on Orthene, its well known that Orthene’s rainfastness is slow and if you can, give it a full 24 hours. I’ve seen my best control with Orthene when we have 48 hours of no rainfall behind an application. Adjuvants may help decrease the time required to be rainfast somewhat but there’s no substitution for a day of dry weather behind an application.

Bollworm moth in cotton bloom
Bollworm moth in cotton bloom

Bollworm egg lay is picking up in a few places around West TN. So far, I haven’t heard of any failures in 3-gene cotton in Tennessee or the Midsouth. It is highly unlikely you will have to spray for worms in any of our triple gene varieties. Our monitoring efforts of Bt corn, which can help forecast issues in cotton, have shown no survivorship in VIP corn. Double Pro varieties, which are equivalent to BG2, are heavily infested with worms and any BG2 cotton should be scouted closely and applications made on our 20% egg threshold.

Soybeans for the most part have been very quiet for much of the growing season. Recently, I noticed a large increase in kudzu bugs and stink bugs infesting soybeans, this is to be expected since we’re reaching the later part of summer. Also, with much of our corn acres reaching dent or past, I would expect to see a decent surge in stink bug numbers as we continue into August. Pyrethroids are good options for almost every pest we face in beans late season. Lingering populations of resistant brown stink bugs may require a premix insecticide (Endigo, Leverage, etc) or the addition of a 0.5 lb of orthene with your pyrethroid.


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