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
With the exception of Hanover, trap captures have declined since last week. The average nightly corn earworm/bollworm moth black light trap captures for this week (rounded) were: Greensville=18; Hanover=7; Prince George-Templeton=3; Prince George-Disputanta=2; Southampton=8; Suffolk=38. Thanks to our trap operators for their reports! TABLE
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.
Average nightly corn earworm/bollworm moth black light trap captures for this week were: Dinwiddie=54; Greensville=15; Prince George-Templeton=13; Prince George-Disputanta=11; Southampton=22; Suffolk=92. Here is the Table
We have 37% survival in our cypermethrin vial tests (338 corn earworm moths tested from Suffolk, VA).
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 firstname.lastname@example.org. 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.
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.
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.
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 (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.
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:
- Untreated control (UTC): water
- Agree: Bacillus thuringiensis subspecies aizawai strain GC-91
- Spear-Lep + Leprotec: GS-omega/kappa-Hxtx-Hv1a + Bacillus thuringiensis variety kurstaki
- XenTari: Bacillus thuringiensis subspecies aizawai strain ABTS-1857
- PyGanic: Pyrethrins
- 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.
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.
Average nightly corn earworm/bollworm moth black light trap captures for this week were: Dinwiddie=51; Greensville=9; Hanover=3 (first week with more than 0.5 per night); Prince George-Templeton=12; Prince George-Disputanta=3; Southampton=5; Suffolk=17. Here is the Table. At just over 200 vial tests conducted, corn earworm moth survival is 39%.
Please find the 2020 Virginia Tech Eastern Shore Agricultural Research and Extension Center Virtual Field Day available via YouTube. Pre-recorded sessions can be viewed in one playlist or you can pick and choose individual topics using the hyperlinks in the attached program.
The program with clickable links is found by clicking: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/spes/spes-239/SPES-239.pdf
As always, contact us with questions vis email, YouTube comments, or Facebook. Please let us know of any further research or Extension questions that you may have. We hope to see everyone again at our Painter, VA location in person in Summer 2021!
Stay healthy and take care!