Category Archives: Insect

Corn earworm report for July 12, 2018

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Corn earworm moth numbers have been low in local black light traps. Watson Lawrence reported 1.4 per night in Chesapeake; Livvy Preisser averaged 0.6 per night in Isle of Wight; Mary Beahm had zero in Warsaw; we had 0.9 per night in Suffolk this week.

Virginia Cooperative Extension Agents and Virginia Tech employees will be scouting field corn for corn earworm larvae this month as part of Dr. Taylor’s annual survey. They examine ears in five corn fields per county and calculate the average percent infested ears. Corn is a nursery crop for corn earworm–the percent of infested ears can be a useful indicator of the pressure to expect in other crops such as soybean, cotton, peanut, etc. when moths emerge and migrate out of corn. We’ll provide results of the survey in the first week of August.

We have tested 80 corn earworm moths in our cypermethrin vial tests this season, with only 8% surviving the 24-hour exposure to 5 micrograms/vial of cypermethrin. It would be great to see moth survival remain that low, but we need to continue testing to see what happens when we get the flight out of corn and later into the season.

Corn earworm found in Virginia peanut fields

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Peanut scouts in Suffolk today found fields with above threshold numbers of corn earworm/tobacco budworm (4 per row foot). Fields previously treated recently with chlorpyrifos may be at higher risk because they have fewer beneficial predators.

Black beat cloths can aide in sampling. However, shaking and slapping plants will dislodge worms onto soil for easy counting. Make sure and check around the base of the plant when using either method.

Feeding damage shows up in the form of holes in foliage. Worms may also feed on terminals and flowers so scouting for damage alone is not recommended. Peanuts can lose a lot of leaf material without losing yield, but drought-stressed or herbicide injured plants are at higher risk for yield-loss. Do not spray unless necessary. Recent dry weather in combination with broad-spectrum insecticides can flair spider mites.

Pyrethoids are a common choice for earworm control in Virginia and most products can be tank mixed with a fungicide to save money. Always read and follow label instructions. Pyrethroids are losing efficacy against earworm and we have experienced spray failures in other crops (soybean, cotton, sweet corn). Budworm have been resistant to pyrethroids for some time. You will not be able to distinguish these two species in the field. Refer to NCSU video for details. Do not expect complete control of large worms or high populations. Alternative products labeled in peanut include Prevathon, Besiege, Steward, Radiant, Intrepid Edge, and Blackhawk. A list of products and rates is included in Virginia Tech’s Pest Management Guide.

Plant bug control in blooming cotton

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Tarnished plant bugs continue to be a problem in some Virginia cotton fields. This week, scouts found 14 of 32 fields over the pre-bloom threshold (8 per 100 sweeps) and increasing numbers of nymphs. Drop cloth sampling is recommended for blooming cotton and counting squares is no longer a good indication of feeding. Threshold is 2-3 bugs per sample. Check out this short video (https://www.youtube.com/watch?v=XRnZhLczZJ0) if you have questions on how to use this method or are unsure of what nymphs look like. Dirty blooms indicate feeding, but active populations should be confirmed before a spray is made.

As cotton begins to bloom, neonicotinoids (e.g., Admire Pro, Centric, Belay) lose efficacy and I recommend rotating to a pyrethroid, a pyrethroid/acephate mix, or Bidrin. These products will  also control stink bugs if present. Transform is not labeled in Virginia, but our representative in Richmond is working hard to get us a Section 18 and I hope to have one in place by next year at the latest. All of these products will kill beneficial predators in your field. This is a concern as we near bollworm egg lay in cotton.

I encourage you to treat for insect pests only when thresholds are reached. Plant bug control will likely be needed through mid-August when populations peak, even in fields that have been previously sprayed. Spider mites, aphids, and bollworm (in two-gene cotton) risk increases with each broad-spectrum insecticide use, as does the risk for sprayer fatigue.

Special thanks to graduate student Seth Dorman and crew for their continued scouting efforts.

Walk Your Fields

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For greater soybean yields, one of the best things that you can do is walk your fields.  Many problems reveal themselves during the summer.  Actions taken or not taken can be very noticeable.  By walking fields, we can see what’s working and what’s not working.  Certain problems can be solved, some cannot.  For those that cannot be solved this year, we can do better next season by understanding why we have the problem.  Therefore, a review of how to diagnose your crop will likely beneficial.

A few years ago, I published “Troubleshooting The Soybean Crop“.  Although a little dated, most of the information is still good.  This publication will guide you through how to go about diagnosing problems, includes a vegetative- and reproductive-stage outline with lots of photos, and also includes a sample crop scouting and diagnostic form.  You can download a view a PDF copy, or contact me – I still have a few hard copies left.  By following some general guidelines, one can become quite good at diagnosing problems.  Below is a summary.

First, document everything!  Memories tend to fade.  We often forget or overlook details. You can document by taken notes (many phone apps or iPad/tablets work well for this).  Make a recording.  Take pictures – this is especially useful when you need help – and send those photos to others.

PRELIMINARY FACT FINDING.  You can obtain plenty of information before you even get to the field.  Although I call this preliminary (as if you’ve not seen the problem), you may need to go back to the office to refresh your memory of what you did.  Information that can be acquired beforehand or back in the office includes:     

  • Cropping History
  • Equipment
  • Soil Information
  • Weather
  • Pest Management Information
  • Tillage and Other Cultural Practices

THE FIELD VISIT

  • Take all materials and equipment needed (e.g., phones, paper, shovel, plastic bags, soil probes, etc.)
  • Windshield/Whole Field Investigation
  • Above-Ground Inspection
  • Take Appropriate Plant or Soil Samples
  • Equipment Check
  • Interaction with Others
  • Document Everything!

ANALYSIS OF DATA AND FINDINGS

  • Patterns
  • Look-Alike Symptoms
  • Interacting Factors/More Than One Problem

DRAWING A CONCLUSION. Review the facts and data.  Eliminate unlikely causes.  Validate likely causes.  You may be able to drawn a conclusion in the field, but lab analysis may be needed.

FOLLOW UP. Revisit the field.  If you took corrective action, did it work?  Why or why not?

This is a very rough outline of the guide.  Again, if you want a hard copy of Troubleshooting The Soybean Crop, contact me.

armyworm in VA small grains

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I have received several reports from Virginia Beach and Chesapeake of armyworms infesting wheat and hay in large numbers. Neighboring regions of NC are experiencing similar outbreaks.

Overall, these infestations are rare in our state, but scouting is recommended. Fields treated previously with pyrethroids may be at higher risk because they contain fewer natural enemies to combat pest outbreaks. Armyworms feed at night and may be found under residue and at the base of plants during the day. Oftentimes, they can be seen curled into a c-shape (see photos below). Thresholds are one larvae (0.75 in or longer) per linear foot in barley and 2-3 per foot in wheat. Refer to Chapter 4 of Virginia Tech’s “Pest Management guide: Field Crops” for products and rates labeled for armyworm control in our state. Pay attention to PHI before making an application. Pyrethroids can be effective against armyworm. Good coverage is critical, especially in high residue fields.

Photos courtesy of JB Rigg, Helena Chemical.

Section 18 for sulfoxaflor (Transform WG) on sorghum for sugarcane aphid

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The EPA has granted a Section 18 for the use of Transform WG (50% a.i. sulfoxaflor) on sorghum for managing sugarcane aphid in certain counties in Virginia. The expiration date is November 30, 2018. All applicable directions for use, restrictions, and precautions on the label, and Worker Protection Standards, must be followed except as modified in the Section 18 document. In part, the Section 18 lists a foliar application rate of 0.75-1.5 oz of product per acre, with a maximum of 2 applications per year, resulting in a seasonal maximum application rate of 3.0 oz of product per acre per year. Please be sure to read and follow the entire label and Section 18. Thanks to the Virginia Department of Agriculture and Consumer Services, Office of Pesticide Services, for their assistance.

Black light trap report for Sep. 28, 2017

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Average nightly black light trap catches of corn earworm moths this week were: Southampton=0.3; Prince George (Templeton)=6; Prince George (Disputanta)=4; Hanover=2; Suffolk=26. Here is the data table: BLT_28_Sep_2017

Most traps are being stowed now. We greatly appreciate the reports this season from Watson Lawrence (Chesapeake); Mike Parrish and Angela Duncan (Dinwiddie); Laura Maxey-Nay (Hanover); Scott Reiter (Prince George); Mary Beahm (Warsaw); LIvvy Preisser (Southampton); and Sally Taylor and her entomology team (Suffolk). We also want to thank the growers who hosted the traps on their farms.

Eastern Shore AREC Field Day CANCELED!

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Due to impending rain Tuesday and Wednesday and already saturated soils, the Eastern Shore AREC field day scheduled for Wednesday, September 13, 2017 has been canceled. Let’s hope Hurricane Irma keeps tracking further west. We certainly do not need any more rain!

Insect update for Sep. 7, 2017

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Most reporting black light trap stations this week had decreased corn earworm moth captures (except for Chesapeake remaining constant). Nightly averages were Chesapeake = 11; Southampton = 1; Suffolk = 8; and Warsaw = 4 moths. Here is the data table:  BLT_7_Sep_2017

No brown marmorated stink bugs were caught this week in the black light traps.