Category Archives: Pest Group

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.

Peanut iPiPE and Disease Advisories

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Especially with all the wet weather we have been having in much of the region, it is time to start thinking about peanut diseases. We do not typically see a lot of disease until the canopy closes, but once the vines are touching the environment within the canopy becomes favorable for disease development. Leaf spot programs should be applied beginning at early beginning pod then according to a calendar-based (usually 14 day intervals) or advisory based program. The leaf spot advisory for Virginia can be found at https://webipm.ento.vt.edu/cgi-bin/infonet1.cgi. Some keys to a successful leaf spot fungicide program include:

  1. Make the first application at the appropriate time (not too late).
  2. Apply fungicides regularly before leaf spot outbreaks are observed (once disease is present it is difficult to slow down the epidemic).
  3. Stick to a regular calendar-based program or utilize leaf spot advisories.
  4. Be mindful of fungicide resistance management (rotate chemistries and/or tank mix with chlorothalonil).
  5. Scout for soil-borne diseases and utilize fungicides with activity against both leaf spot and other target diseases (e.g. for both late leaf spot and southern stem rot control use a product such as Provost, Elatus, Priaxor, etc.).

Data are currently being collected to improve both leaf spot and Sclerotinia advisories and to develop a southern stem rot fungicide advisory for peanut. This is being conducted through the Peanut iPiPE program. The Integrated Pest Information Platform for Extension and Education (iPiPE) is a program that allows farmers and extension agents to share information with each other through the internet.  iPiPE works by allowing users to enter pest data such as presence and severity of diseases or insects. This data will be shared with everyone in an effort to create a more precise system of pest monitoring and management. The Plant Pathology program at the Virginia Tech Tidewater AREC is leading the Peanut iPiPE and using it to improve disease advisories based on observations of disease onset in peanut fields throughout the region. Two undergraduate interns are currently scouting for peanut diseases in the region, and they will enter disease observations into the iPiPE database.

Disease and pest observations can be easily uploaded to the database through a mobile phone app or the online platform. We are encouraging anyone who scouts peanuts to help us collect disease observations. To become a participant, you can request an iPiPE account by visiting the iPiPE platform (http://www.ipipe.org/). Detailed information on the iPiPE platform and a user guide for the mobile app can be downloaded below. Alternatively, you can email disease observations to Dr. Hillary Mehl (hlmehl@vt.edu). In addition, if you are located in southeastern Virginia or northeastern North Carolina and are interested in having your peanut crop scouted for diseases by our iPiPE interns, please contact us.

Peanut iPiPE Stakeholder Card 2018

Peanut iPiPE Users Guide 2018

For more information or questions regarding the Peanut iPiPE contact Dr. Hillary Mehl (hlmehl@vt.edu).

 

 

 

New Crop Disease Management Resources

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Though it has been around for several years, the Crop Protection Network (CPN) has recently added several publications on disease management in corn, soybean, and small grains that are relevant to growers, crop consultants, and extension personnel in Virginia and the surrounding region. These can be accessed at the CPN website cropprotectionnetwork.org. As stated on the website:

“The Crop Protection Network (CPN) is a multi-state and international partnership of university and provincial Extension specialists, and public and private professionals that provides unbiased, research-based information. Our goal is to communicate relevant information to farmers and agricultural personnel to help with decisions related to protecting field crops.”

Extension specialists throughout the country (including myself) contribute to the publications and other resources posted on the website. An example of a recent publication on optimizing fungicide use for control of Fusarium head blight can be downloaded below. The CPN library includes over 30 publications on crop management, and additional publications are in development.

CPN-3001-Optimizing Fungicide Use for FHB

Wheat Disease Update – May 24, 2018

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Fusarium head blight (FHB) risk for Virginia continues to be to high throughout the state due to recent wet, warm weather (http://www.wheatscab.psu.edu/). Most of the wheat is past the flowering stage and no longer at risk, but later flowering wheat may still need a fungicide application. Triazole fungicides including Prosaro, Caramba, and Proline are recommended. Do not apply fungicides containing a strobilurin since this can increase DON. For wheat that is past flowering, a fungicide application will not reduce FHB or DON contamination of the grain. Grain harvested from fields with signs and symptoms of FHB should be kept separate from non-infested grain.

For assistance with disease identification or management recommendations, contact Dr. Hillary L. Mehl, Extension Plant Pathologist (hlmehl@vt.edu).

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.