Category Archives: Uncategorized

Herbicide Resistant Weeds Workshop

Palmer amaranth infesting a soybean field
The workshops will be virtual via Zoom on Tuesday Dec. 8th and Tuesday Dec. 15th. On both days, choose the time that works best for you: 8-10 am OR 6-8 pm. Optional in-person “watch party” meetings offered at several locations.

Register at: https://go.umd.edu/IWM  

Topics: Session One: Tues Dec 8th 8-10 am OR 6-8 pm
Herbicide Resistance- What is It?
Mechanisms of Action-How to Choose Herbicides
Creating Effective Herbicide Plans  

Session Two: Tues Dec 15th 8-10 am OR 6-8 pm
IWM with a focus on Palmer Amaranth, Common Ragweed, and Marestail
Local Perspectives on Resistance Management
Putting It All Together: Creating a Weed Management Plan

Speakers:
Dr. Michael Flessner and Dr. Vijay Singh, Virginia Tech
Dr. Mark VanGessel, University of Delaware
Dr. Kurt Vollmer and Ben Beale, University of Maryland

CCA Credits will be offered.
For More Information Contact:
Ben Beale at 301-475-4481 or Kurt Vollmer at 410-827-8056 28

Fire ants in crop fields and near homes – southeast VA

Fire ant mound around brace roots of corn plant, Suffolk, VA.

We have high numbers of fire ant mounds in our crop fields and around our farms this year. There have been some unfortunate encounters and this message is to make you aware of what these mounds look like and the potential for injury. Mounds look like large piles of loose dirt (keep in mind they have to start small at some point). They are often found around fence posts and mailboxes, but many are located in fields, pastures, and lawns. Field borders and paths are frequently infested. Fire ants sting, just like wasps and bees, and some people will be allergic and require medical interventions. People that are not allergic will have itchy, painful welts that often fill with fluid and may take days or a week or more to heal. Usually, you will have dozens or even hundreds of stings. This is because the swarm very fast and wait to sting all at once. Keep in mind that I have lived around them most of my adult life in North Carolina and we have come to accept them as part of our environment and have learned caution and awareness. I have been stung multiple times, usually once every few years, and usually when I am scouting crops. Be aware of where your feet are standing. Walk quickly when crossing a field because you can disturb them and get away without injury. Treatment options are below for mounds located near homes and barns. You do not want children or young animals near these things.

Fire ant mound around edge of soybean field, Suffolk, VA.

I would not attempt to clear your crop fields. A single acre can contain hundreds of mounds and millions of fire ants. Fire ants are predators and will eat caterpillars and other insect pests. They will not eat seeds and plants. Large mounds can damage equipment in rare cases. Products exist that can be applied to turf and lawns with year-long residuals (e.g., TopChoice). These products require a pesticide applicator license to purchase. Baits (e.g., Advion) are an alternative if you are not licensed to apply insecticides. These can be purchased online, many local retailers do not carry them yet. Surface treatments do not work because the colony can live very deep underground. Do not attempt to treat once the weather turns cold because it will not work. Wait until spring. Pray for a cold winter.

Be safe y’all and stay healthy. As always, reach out to me if you have questions or concerns. Keep in mind that I am NOT an urban or ornamental entomologist and I am NOT trying to sell you any specific product. FOLLOW THE LABEL WITH ANY INSECTICIDE.

Corn earworm report–September 24, 2020

Corn earworm moth black light trap catches were low this week, averaging from 2 to 6 per night (Greensville=3; Hanover=2; Southampton=6; Suffolk=2). Most trap operators will be shutting off their traps by the end of this month. We greatly appreciate the efforts of cooperating growers, Virginia Cooperative Extension Agents Mike Parrish, Sara Rutherford, Laura Maxey-Nay, Scott Reiter, and Josh Holland, and Tidewater Agricultural Research and Extension Center’s Daniel Espinosa. TABLE

Corn earworm report–Sep. 10, 2020

Average nightly corn earworm/bollworm moth black light trap captures for this week were: Greensville=28; Prince George-Templeton=5.5; Prince George-Disputanta=7; Southampton=17; Suffolk=76. Here is the Table

For soybean, here is the tool that calculates the corn earworm larval threshold number based on user input values for sampling techinque (sweep net or beat cloth), cost of insecticide application, price of beans, and row width: threshold calculator

We have done 391 vial tests so far this season, with 35% of moths surviving the 24-hour exposure to the pyrethroid cypermethrin at the rate of 5 micrograms per vial.

Pickleworm found in Virginia – a pest threat to pumpkins, squash and other cucurbit crops

This week, my PhD student, Sean Boyle, observed pickleworm holes in our zucchini and squash in Whitethorne, VA near Blacksburg. This is the first that we’ve seen this pest in 2020. If you have noticed this pest in your area, please let me know – email tkuhar@vt.edu. The pickleworm, Diaphania nitidalis (Stoll) is a tropical moth pest of cucurbit crops including pumpkins, squash, and cucumbers (Fig. 1). It is typically a pest in the southern U.S. and does not overwinter in Virginia. The past few years, the pest has made its way northward in late summer on wind and storm fronts. Several pumpkins growers in Virginia have suffered damage from this pest in since 2017 usually following some August summer storms.   

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Fig. 1. Pickleworm moth.
Fig. 2. Pickleworm larva and entrance hole on pumpkin.

Moths fly to flowering pumpkins, squash, or cucumbers and deposit their eggs. A single female moth can lay up to 400 eggs usually on cucurbit flowers.  Larvae feed on flowers (Fig. 2) and bore into fruit leaving a characteristic perfectly round hole often with sawdust-like fecal material around it as well.     

Management. Pickleworm is very difficult to predict or monitor for as eggs are very tiny, moths fly at night, but are not attracted to lights, and there is no commercially-available pheromone lure.  As a result, cucurbit growers in the South often apply insecticides weekly during the fruiting stages until final harvest.  Pyrethroid insecticides can be effective at controlling this pest if sprayed in a timely manner (i.e., lambda-cyhalothrin, permethrin, bifenthrin, Baythroid XL, Mustang Max, etc.). Pyrethroids are often used because of their low cost and because they also control squash bugs and cucumber beetles, but they are not IPM compatible and can result in outbreaks of secondary pests such as aphids.  Usually two or more sprays of pyrethroids in late summer can cause severe aphid problems leading to honey dew build up on plants. Other insecticides that control pickleworm include: the spinosyn productss, Radiant and Entrust, the diamide insecticides, Coragen and Harvanta, the insect growth regulator (IGR) Intrepid, and the lepidopteran-targeting insecticide Avaunt eVo.  All of these products will have less nontarget impacts than pyrethroids and will also control pickleworm.                                                                                           

Peanut Maturity in SE Virginia on Aug 25, 2020

This year, peanut is nowhere near where it was last year, from the pod maturity point of view. The pictures below show 100% white (immature) pods from Bailey planted on May 14, 2020, and collected on Aug 25. Last year, on Aug 27, pods of Bailey planted on May 3, 2019, ranged from 10% white to 25% brown and black (fully mature), with the majority in yellow and orange mesocarp color denoting substantial progress towards physiological maturity. Indeed, in 2019, peanut was planted earlier than this year, but this only explains part of the reason why this year peanuts are maturing later than in 2019. The other part comes from the dry and hot July, when pollination, and growth of pegs and pods were slowed down.  Tropical storm and other rain events at the end of July benefitted pod development, but maturity is still delayed from the last season. I am showing pictures only from Bailey, as the main cultivar grown on 50% of the peanut acreage this year; but we looked at Sullivan, Emery and Wynne as well and they look similar with Bailey. This year, we also noticed on all these cultivars a fair amount of Southern corn rootworm and other pod damage, regardless the soil where pod samples were collected at the Tidewater AREC. I will continue updates on peanut maturity every other week.

Bailey planted May 14, 2020 and pod blasted on Aug 25, 2020
Bailey planted May 3, 2019 and pod blasted Aug 27, 2019
Bailey pegs and pods on July 20, 2020.
Bailey pods with Southern Corn Rootworm and other damage

Corn earworm moth trap catch around Blacksburg, VA and results of an insecticide evaluation on hemp

This article was co-authored by Virginia Tech Entomology Ph.D. student, Kadie Britt.

Here are the corn earworm moth catch numbers from a handful of pheromone traps that we have set up in hemp fields and one sweet corn field around Blacksburg, VA. Trap catch appeared to peak around mid-August with moths emerging from cornfields and has subsided a little toward the end of August. Crops such as soybeans, hemp, tomatoes, and sweet corn are still at risk to this important pest.

Corn earworm moth catch in Heliothis traps baited with corn earworm Hercon sex pheromone lures.

Corn earworm (CEW) is the insect pest of greatest concern to hemp grown outdoors in Virginia and other states. For more information about this pest’s biology and behavior in hemp, see this factsheet: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/ENTO/ento-328/ENTO-328.pdf.

We have already started to see worms feeding on hemp throughout Virginia. CEW feeding on hemp causes mechanical damage to buds, allowing environmental pathogens to enter crop material, ultimately leading to bud rot. Bud rot is visible and present in hemp crops right now but is not prevalent just yet. Managing populations early on will be key to reducing crop injury this season.

Corn earworm larva on hemp plant in Virginia. Photo by Kadie Britt.

Strict regulations on pesticide applications to hemp prevent the use of many available insecticides. We have conducted a laboratory experiment to evaluate the efficacy of some products that are currently allowed for use in hemp in Virginia as well as Pyganic, which is not labeled on hemp, but is a widely used organic insecticide.

Treatments included in the August 19, 2020 bioassay included:

  1. Untreated control (UTC): water
  2. Agree: Bacillus thuringiensis subspecies aizawai strain GC-91
  3. Spear-Lep + Leprotec: GS-omega/kappa-Hxtx-Hv1a + Bacillus thuringiensis variety kurstaki
  4. XenTari: Bacillus thuringiensis subspecies aizawai strain ABTS-1857
  5. PyGanic: Pyrethrins
  6. PyGanic + PBO (insecticide synergist): Pyrethrins + Piperonyl butoxide

To conduct this bioassay, corn earworm larvae (3rd to 5th instars) were collected from untreated sweet corn grown at Kentland Research Farm in Whitethorne, VA. Untreated hemp seed heads were collected from grain hemp, variety ‘Joey’, grown at the Urban Horticulture Center farm in Blacksburg, VA. Seed heads were dipped in spray tank concentrations of each insecticide at the high labeled rate and placed into 1 oz. diet cups. Larval corn earworms were placed directly on top of treated material. Mortality was evaluated at 1, 2, 3, and 4 days after the experiment was set up (Figure 3). PyGanic + PBO provided significantly greater efficacy against CEW than all other products tested with only 6.5% of worms surviving after 4 days. The addition of the synergist is needed for effective control with Pyganic due to pyrethroid resistance development in this pest.  Unfortunately, Pyganic is not currently labeled for use on hemp in Virginia.  Agree, XenTari, and PyGanic without PBO all performed similarly with 50.3%, 53.5%, and 59.9% of worms surviving after 4 days, respectively.

Survival after 4 days of field-collected corn earworm larvae placed on hemp seed heads that were dipped in spray tank concentrations of various organic insecticides. All products except Pyganic are permitted for use on hemp in Virginia.

Looking ahead this season, insecticide research trials in CBD hemp will be conducted in Blackstone with all of the aforementioned products plus many more. We will continue doing lab bioassays with CEW and other insecticides that are allowed for use in hemp at this time. Results will be shared as they become available.