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Sweet corn moth trap numbers for VA counties – week of July 24, 2017

Sweet corn farms are being monitored around Virginia for the two most important pests attacking the ears, corn earworm and fall armyworm.  Moth Trap Catch Data are being recorded by:  Katlyn Catron  (Montgomery Co.); Jason Cooper (Rockingham Co.); Ursula Deitch (Northampton Co.); Helene Doughty (Accomack Co. & Virginia Beach); Kenner Love (Rappahannock Co.); Laura Maxey Nay (Hanover Co.); Steve Pottorff (Carrol Co.); Stephanie Romelczyk  (Westmoreland Co.); Laura Siegle (Amelia Co.); Rebekah Slabach (Halifax Co.); and Mark Sutphin (Frederick Co.).

This week we observed some big jumps in corn earworm moth catch at some locations such as the Bridge Tunnel in Northampton County, the ESAREC in Accomack Co., and Hanover Co.   We still have not seen very many  fall armyworm moths yet, only a few moths here and there in VA. For corn earworm, moth trap catch of less than 1 per night means  low pest pressure and sweet corn sprays can probably be spaced 5-6 days apart during silking.  However, a catch of >1 or >13 moths per night means moderate and high pest pressure, respectively, and a more frequent spray interval (every 3 or 2 days) is justified.  Here are the trap catch results (moths per night) for several locations around Virginia for this week (note we do not have data for all locations):

Week of July 24 (avg)
Region County Field CEW/night FAW/night
Eastern Shore Accomack ESAREC – cemetery 9.6 1
Eastern Shore Accomack ESAREC – woods 3.4 0
Eastern Shore Accomack ESAREC – sweet corn 4.6 0
Eastern Shore Northampton Bridge Tunnel 60.4 NA
Eastern Shore Northampton Capeville 1 2.1 0
Eastern Shore Northampton Cape charles 6.3 NA
Eastern Shore Northampton Eastville 10.6 1
Eastern Shore Northampton Nassawaddox 0.1 1
Virginia Beach Virginia Beach Pungo 1 11.9 1
Piedmont Amelia Field 1 NA NA
Piedmont Hanover Farm 1 11.0 0.0
Piedmont Hanover Haynes 3.9 0.0
Northern Neck Westmoreland Field 1 6.3 0
Northern Neck Westmoreland Field 2 NA NA
Shenandoah Valley Rappahannock Field 1 0.6 0
Shenandoah Valley Page Field 1 1.7 0
Shenandoah Valley Frederick Farm 1 1.4 1
Shenandoah Valley Frederick Farm 2 5.2 0
Shenandoah Valley Rockingham Farm 1 0.7 1
Shenandoah Valley Rockingham Farm 2 NA NA
New River Valley Montgomery KC 0.0 0
New River Valley Montgomery KO1 2.0 1
New River Valley Montgomery KO2 6.0 1
New River Valley Montgomery WF1 1.0 NA
New River Valley Montgomery WF2 0.0 NA
New River Valley Montgomery WF3 4.0 NA
New River Valley Montgomery WS1 0.0 NA
New River Valley Montgomery WS2 1.0 NA
New River Valley Montgomery WS3 1.0 NA

This project is sponsored by a Specialty Crop Block Grant by VDACS.

Large bollworm flight this year into VA cotton

If blacklight traps at the Tidewater AREC in Suffolk are any indication, we are currently experiencing an unusually large and early bollworm (aka corn earworm) moth flight this year. Average trap catches over the past 4 nights have averaged 70 moths per night. I have included 2016 season-long catches below for comparison.

We have additionally scouted for, and found, eggs in cotton and on silks of late-planted corn. I have included pictures below to help with identification. Our ongoing corn earworm survey has revealed large numbers of worms completing development on Bt corn in multiple counties. I strongly encourage cotton growers who planted Widestrike or Bollgard II this year to be vigilant when scouting fields. In agreement with Dominic Reisig’s (North Carolina State University) 2016 recommendations, entomologists in the Mid-South (Angus Catchot – Mississippi State University) have suggested egg thresholds broken-down by trait package:

WideStrike Cotton: Treat on 10-15% egg lays on bloom tags

BG2 cotton: Treat on 25-30% egg lay on bloom tags.

These thresholds are supported by observations made across the Southeast last year, including in North Carolina and Virginia, that worms have a higher chance of surviving on blooms than on any other part of the plant. These thresholds have not been established through experimentation and I consider them to be extra protective. Budworm eggs are identical to bollworm eggs and this species is controlled by Bt toxins. I have seen both budworm and bollworm moths in cotton this year.

Some growers have planted conventional cotton this year. We have established egg and larval thresholds in Virginia for non-Bt varities:

Eggs: 10 eggs per 100 terminals or 2 eggs per 100 fruiting forms (most cotton we have scouted has reached this threshold)

Larvae: 3 live worms per 100 terminals or 3% damage to squares, blooms, bolls

Currently, we have experienced no unexpected injury to Widestrike III or TwinLink technologies. I would not assume these varieties to be bulletproof in a high pressure year, but I do think that these technologies offer good protection in our area.

I recommend spending the extra money on a worm-specific product instead of relying on pyrethroids. Vial tests in Suffolk have indicated a trend towards resistance for several years and there have been field failures reported south of us this season. Besiege and Prevathon are good choices because they offer residual control. Besiege targets sucking-bug pests in addition to worms. I have had inquiries about Intrepid Edge. Virginia Tech has not tested this product in cotton. It has performed well in soybean tests and in cotton tests in other regions (Jeremy Greene- Clemson University, South Carolina). Keep in mind that no product works well against large larvae. Due to the early nature of this year’s flight, we may experience additional pressure later this season. I will keep you updated on what’s happening in Virginia. Please call if you have anything to report.

Sally 919-801-5366

 

Corn earworm and Fall armyworm trap catch numbers from Virginia sweet corn fields – Week of July 16

Sweet corn farms are being monitored around Virginia for the two most important pests attacking the ears, corn earworm and fall armyworm.  Moth Trap Catch Data are being recorded by:  Katlyn Catron & John Few (Montgomery Co.); Jason Cooper (Rockingham Co.); Ursula Deitch (Northampton Co.); Helene Doughty (Accomack Co. & Virginia Beach); Kenner Love (Rappahannock Co.); Laura Maxey Nay (Hanover Co.); Steve Pottorff (Carrol Co.); Stephanie Romelczyk  (Westmoreland Co.); Laura Siegle (Amelia Co.); Rebekah Slabach (Halifax Co.); and Mark Sutphin (Frederick Co.).

This week we have still not seen the fall armyworm flight yet in VA.  A few moths were caught on the Eastern Shore of VA and a couple other locations, but generally they are not in Virginia yet from their migratory flight from the south each summer.  For corn earworm, trap catch of less than 1 per night means relatively low pest pressure and sprays can probably be spaced 5-6 days apart during silking.  However, a catch of >1 or >13 moths per night means moderate and high pest pressure, respectively and a more frequent spray interval (every 3 or 2 days) is justified.  Trap catch increased to high levels on several farms this week throughout the state including Northampton Co., Virginia Beach, Page Co., and Montgomery Co.

Here are the trap catch results (moths per night) for several locations around Virginia for this week (note we do not have data for all locations):

Week of July 16 (avg)
Region County Field CEW/night FAW/night
Eastern Shore Accomack ESAREC – cemetery 4.4 3
Eastern Shore Accomack ESAREC – woods 1.1 0
Eastern Shore Northampton Bridge Tunnel 33.3 0
Eastern Shore Northampton Capeville 1 1.5 0
Eastern Shore Northampton Cape charles 3.0 NA
Eastern Shore Northampton Eastville 4.5 0
Eastern Shore Northampton Nassawaddox 1.5 0
Virginia Beach Virginia Beach Pungo 1 15.7 0
Piedmont Amelia Field 1 4.0 0.2
Piedmont Hanover Farm 1 3.7 0.0
Piedmont Hanover Haynes 1.1 0.0
Northern Neck Westmoreland Field 1 10.0 0
Northern Neck Westmoreland Field 2 3.7 1
Shenandoah Valley Rappahannock Field 1 5.0 0
Shenandoah Valley Page Field 1 12.0 0
Shenandoah Valley Frederick Farm 1 7.4 0
Shenandoah Valley Frederick Farm 2 3.2 0
Shenandoah Valley Rockingham Farm 1 0.3 0
Shenandoah Valley Rockingham Farm 2 1.0 0
New River Valley Montgomery KC 1.0 0
New River Valley Montgomery KO1 3.3 0
New River Valley Montgomery KO2 9.3 0
New River Valley Montgomery WF1 16.3 NA
New River Valley Montgomery WF2 4.3 NA
New River Valley Montgomery WF3 13.0 NA
New River Valley Montgomery WS1 17.3 NA
New River Valley Montgomery WS2 19.0 NA
New River Valley Montgomery WS3 36.7 NA

Corn earworm and fall armyworm trap catch numbers in Virginia – Week of July 10, 2017

 

Corn earworm larva in sweet corn.

Corn earworm and fall armyworm are two important pests of a number of agricultural crops in Virginia.  Sweet corn, in particular, is extremely vulnerable to attack by the larvae (or caterpillars) of these moth pests.  Monitoring moth catch numbers in pheromone-baited traps can help IPM decision-making.  See at the end of this post the Action threshold for spraying insecticides on sweet corn based on corn earworm trap catch.  In general trap catch less than 1 per night means relatively low pest pressure and sprays can probably be spaced 5-6 days apart during silking.  However, a catch of >1 or >13 moths per night means moderate and high pest pressure, respectively and a more frequent spray interval is justified.

In 2017, we are monitoring these pests on sweet corn farms in 11 different counties in Virginia.  Moth Trap Catch Data are being recorded by:  Katlyn Catron & John Few (Montgomery Co.); Jason Cooper (Rockingham Co.); Ursula Deitch (Northampton Co.); Helene Doughty (Virginia Beach); Kenner Love (Rappahannock Co.); Laura Maxey Nay (Hanover Co.); Steve Pottorff (Carrol Co.); Stephanie Romelczyk  (Westmoreland Co.); Laura Siegle (Amelia Co.); Rebekah Slabach (Halifax Co.); and Mark Sutphin (Frederick Co.)

Here are the trap catch results (moths per night) for several locations around Virginia for this week (note we do not have data for all locations):

Region County Field CEW  moths/night FAW moths/night
Eastern Shore Accomack ESAREC 1.1 0
Eastern Shore Virginia Beach Pungo 1 1.6 0
Eastern Shore Virginia Beach Pungo 2 3.9 0
Eastern Shore Northampton Bridge Tunnel 6.6 0
Eastern Shore Northampton Capeville 1 3.6 0
Eastern Shore Northampton Capeville 2 0.0 0
Eastern Shore Northampton Eastville 0.6 0
Eastern Shore Northampton Nassawaddox 1.0 0
Piedmont Amelia Field 1 2.7 0
Piedmont Hanover Field 1 2.1 0
Piedmont Hanover Field 2 1.0 0
Northern Neck Westmoreland Field 1 3.0 0
Shenandoah Valley Rappahannock Field 1 1.0 0
Shenandoah Valley Frederick Field 1 2.3 0
Shenandoah Valley Frederick Field 2 3.5 0
New River Valley Montgomery Whitethorne 1.9 0
New River Valley Montgomery Wall field corn 1.1 0
New River Valley Montgomery Wall sweet corn 20.8 0

 

Action threshold: Number of Corn Earworm Moths Caught in Pheromone trap
Per Day Per 5 Days Per Week Spray Interval for sweet corn
<0.2 <1 <1.4 No Spray
0.2 – 0.5 1.0 – 2.5 1.4 – 3.5 6 Day
0.5 – 1.0 2.5 – 5.0 3.5 – 7.0 5 Day
1.0 – 13.0 5.0 – 65.0 7.0 – 91.0 4 Day
>13.0 >65.0 >91.0 3 Day

 

 

Aerial applications effective for stink bugs

Last week the entomology department followed up on aerial spray applications for stink bugs. These applications were very effective (>98% mortality). If you are considering spraying for this pest in your corn, NCSU recommends bifenthrin as the pyrethroid of choice. This is consistent with spray trials at the Tidewater AREC that showed poor control with lambda-cyhalothrin (karate, warrior II). All pyrethroid insecticides must make contact with the insect to kill it and there will be poor, if any, residual control. We recommend waiting to treat until all wheat is harvested in the nearby area. So far, there have been no infestations at threshold in corn fields that are greater than 1/4 mile from wheat. Currently, we are scouting Virginia’s eastern shore where the wheat harvest is in progress.

 

Failed Corn Stand: Starting Over

Charlie Cahoon and Michael Flessner

Virginia Tech Weed Science

Over the past few days we have had several questions concerning replanting corn behind an already failed corn stand.  Our biggest concern in this situation is how to terminate emerged corn from the first planting.  The best option for small corn (4-8 inch) is clethodim (Select Max or generics).  The label for Select Max (0.97 lb active ingredient/gal) specifies 6 oz/A must be applied at least 6 day prior to replanting.  Clethodim products that contain 2 lb active ingredient/gal and are labeled for this situation should be applied at 3 oz/A, while adhering to the same plant-back restriction.  As is the case with many weeds, timeliness is critical.  Control of larger corn by clethodim is variable (> 8 inches).

Poor corn stand as a result of bird damage. Painter, VA 2017.

Producers not wanting to wait 6 days before replanting should use paraquat (at least 3 pt/A of a 2 lb/gal product or 2 pt/A of a 3 lb/gal product).  Paraquat should not be used alone; adding atrazine (1 pt/A) and suggested adjuvants to paraquat will enhance control.  Research conducted by Dr. Kevin Bradley (University of Missouri) and Larry Steckel (University of Tennessee) concluded Liberty did not consistently control Roundup Ready corn.  Although not listed on the bag, many corn hybrids are tolerant to glufosinate (active ingredient in Liberty).  For these reasons, producers should be wary of using Liberty to terminate a failed corn stand.

Another common question when replanting corn is whether to reapply residual herbicides such as atrazine. Atrazine and other residual herbicides should not be reapplied. If additional atrazine is desired in a postemergence application, just note that the cumulative total atrazine for your first and second planting of corn cannot exceed 2.5 lb active ingredient per acre per year.  Other products have similar restrictions.

On a normal year, growers are usually asking if soybean can be planted behind corn.  And our answer to this is usually no.  This is mostly due to the fact that most everyone uses atrazine preemergence and planting soybean following atrazine if very risky.  The label of most atrazine products says “Do not rotate to any crop except corn or sorghum until the following year, or injury may occur” and “If applied after June 10, do not rotate with crops other than corn or sorghum the next year, or crop injury may occur”.

 

Wheat Disease Update – May 2, 2017

Following last week’s rain, the risk for Fusarium head blight (FHB or scab) infections has increased, and the risk is very high even for moderately resistant varieties in certain portions of the state (see FHB Risk Map). Much of the wheat crop is beyond the early flowering stage, but for fields where wheat is currently flowering a fungicide may be needed to protect the crop from FHB infection and DON contamination. Recommended fungicides include Caramba, Prosaro, and Proline. Fungicides are most effective when applied at the start of flowering and up to a week later. The greatest coverage of the heads can be achieved by applying fungicides in 5 gal/A by air and 15 gal/A by ground with a 300-350 um droplet size and nozzles angled forward at least 30 degrees.

FHB risk on May 2, 2017 for moderately resistant wheat varieties. Susceptible wheat varieties that are currently flowering are at high risk for FHB infection throughout Virginia.

Wheat Disease Update – April 20, 2017

Wheat is beginning to flower throughout Virginia, so it is time to make decisions about fungicide applications for both Fusarium head blight (FHB, also known as scab) and to protect the flag leaf as the grains begin to form. Currently, the risk for FHB is low in most parts of Virginia, even for susceptible varieties. The FHB Risk Assessment Tool can be found at http://www.wheatscab.psu.edu. Keep in mind that this is a prediction tool and it will not predict FHB outbreaks 100% of the time. A current screen shot of the website is shown below. Rains are expected over the weekend, but dry weather over the past several weeks has not favored spore production by the FHB fungus, so risk of FHB infection is expected to remain low for wheat that is flowering over the next week. However, now may still be the time to apply fungicides for foliar diseases including stripe rust, powdery mildew, and leaf blotch. The flag leaf must be protected during grain development to maximize yields. Again, due to the dry weather some areas have very little disease, and scouting is still recommended prior to making a fungicide application. However, there have been numerous reports throughout the region of outbreaks of stripe rust (especially on Shirley) and powdery mildew. Do NOT apply a strobilurin or fungicide pre-mix containing a strobilurin after flag leaf emergence (Feekes 9) since this can increase DON contamination in the grain. Prosaro, Caramba, and Proline are the most effective products for reducing scab and DON contamination, and these fungicides will also control foliar diseases such as leaf blotch, stripe and leaf rust, and powdery mildew. A fungicide efficacy table for wheat can be found in a previous post.

Screen shots from the Fusarium Head Blight Risk Assessment Tool (http://www.wheatscab.psu.edu) on April 20, 2017. Currently, risk of FHB infection in wheat that is flowering is low in most parts of Virginia. The exception is along the Eastern Shore where conditions are typically more humid and favorable for spore production by the FHB fungus. For susceptible varieties such as Shirley, FHB risk is moderate to high in some areas. However, for moderately resistant varieties such as Hilliard, the risk is currently low. This illustrates the importance of variety selection in management of FHB and DON contamination in wheat.  

Wheat Disease Identification Guide

Copies of a Wheat Disease Identification Guide from Kansas State are now available and can be requested from Dr. Hillary Mehl at the Tidewater AREC (hlmehl@vt.edu). A PDF version of the guide can be downloaded here. Though not specific to Virginia, many of the diseases included in the guide occur in our region and detailed descriptions of symptoms and management recommendations are included. As always, if confirmation of a disease is needed for wheat or other agronomic crops, plant samples can be submitted to the Virginia Tech Tidewater AREC (6321 Holland Rd. Suffolk, VA 23437). When submitting samples, be sure to fill out the Plant Disease Diagnostic Form with as much information as possible as this will assist us with an accurate diagnosis. The form can be downloaded here: Plant Disease Diagnostic Form