The allium leafminer (ALM), Phytomyza gymnostoma (Loew) (Diptera: Agromyzidae), is an invasive fly species that was first recorded in the U.S. in Pennsylvania in 2015. The pest attacks onions, garlic, and leeks where the larvae (maggots) feed on plant tissue by mining the plant causing wilting and possible death. This new pest to the mid-Atlantic area is a long grey-black fly with a distinctive yellow or orange patch on the top of its head, yellow sides and “knees” (femur-tibia junction), and white halteres (knobs as second pair of wings). The larvae are a typical whitish maggot. Adult females repeatedly puncture leaves with their ovipositor, resulting in a line of small white dots. Leaves can be wavy, curled and distorted. Larvae mine leaves and move into bulbs and leaf sheathes where they pupate. This invasive pest was recorded in southwest Virginia in 2021 and has been found in Montgomery, Carroll, Botetourt, and Bedford Counties in Virginia. Please pass this information on to VCE personnel and Master Gardeners so that we can track the spread of this invasive pest in The Commonwealth. The photos below show the life stages of this pest. The egg laying scars (perfect line of tiny circle marks on stems) are telltale sign.
Allium leafminer larva (photo by Sean Boyle, Virginia Tech)Allium leafminer larva found in Blacksburg, VA in September 2021. (photo by Sean Boyle Virginia Tech)
Oviposition scars by allium leafminer. Photo by Tom Kuhar.
Control: Covering plants in April-May, or September-October, during the adult flights, can exclude the pest. A number of systemic and contact insecticides can provide effective control including neonicotinoids, diamides, spinosyns, and pyrethroids. Products registered for allium leafminer control include:
Mustang Maxx 2.88 to 4.0 fl oz/A zeta-cypermethrin
Warrior 1.28 to 1.92 fl oz/A lambda-cyhalothrin
Scorpion 35SL 8.75 to 10.5 fl oz/A dinotefuran – soil
Scorpion 35SL 5.25 to 7.0 fl oz/A dinotefuran – foliar
Venom 70SG 5.0 to 6.0 fl oz/A dinotefuran – soil
Venom 70SG 3.0 to 4.0 fl oz/A dinotefuran – foliar
Entrust SC (OMRI) 3.0 to 6.0 fl oz/A spinosad
Radiant SC 6.0 to 10.0 fl oz/A spinetoram
Trigard 75WSP 2.66 oz/A cyromazine
Exirel 13.5 to 20.5 fl oz/A cyantraniliprole
Minecto Pro 7.0 to 10.0 fl oz/A cyantraniliprole + abamectin
From Daniel Frank (Virginia Tech Pesticides Program):
As of February 28, 2022, all food tolerances for chlorpyrifos were revoked and any new applications of chlorpyrifos will render any food treated as adulterated and ineligible to be distributed in interstate commerce. In issuing the final rule, EPA found that it could not determine that there is a reasonable certainty of no harm from aggregate exposure, including food, drinking water, and residential exposure, to chlorpyrifos, based on currently available data and taking into consideration all currently registered uses for chlorpyrifos. EPA has a dedicated webpage including information for anyone in possession of chlorpyrifos products for use on food when tolerances expire. According to EPA, • Applicators should discontinue use on food. If the products label allows for use in other non-food settings, it may continue to be used for those non-food purposes. • Chlorpyrifos products should not be disposed of in landfills for industrial or municipal solid waste. • Current options for dealing with chlorpyrifos products labeled for use on food: o Store chlorpyrifos products until there is an opportunity for appropriate disposal. Details on proper storage can be found using the following links: https://www.epa.gov/safepestcontrol/storing-pesticides-safely https://www.epa.gov/pesticide-worker-safety/requirements-pesticide-storage o Appropriately dispose of these products as specified by the state. Information regarding the VDACS pesticide collection program including the 2022 service area and dates/times of collection were previously sent out and are also available here. Should any additional information become available related to the rule including other options for final disposition of the product, I will be sure to share that information.
Regards,
Daniel
— Daniel L. Frank Director of Pesticide Programs Virginia Tech 302 Agnew Hall 460 West Campus Drive Blacksburg, VA 24061 540-231-3430 vtpp.org
By: Tom Kuhar, Alejandro Del Pozo, and Sally Taylor Virginia Tech Department of Entomology
In the past week, many areas of Virginia have experienced severe outbreaks of fall armyworms (FAW), which have completely destroyed lawns, sod plantings, hayfields, and alfalfa fields. As you would imagine, we have gotten a lot of calls about these pests. We’ve included some of the FAQ below.
Fall armyworms collected from a sod farm in Virginia last week. Lawn in Lancaster destroyed by fall armyworm, which fed upon the fescue grass only and left behind other grass and plant species.
Who’s being harmed the most by armyworms?
Lawns with turf-type fescue grass are being hit the hardest across Virginia. Alfalfa and hayfields are also being attacked.
Alfalfa field in Virginia destroyed by fall armyworms last week.
2. What crops are at risk? While FAW are known to attack a number of crops such as grasses, small grains, corn, sorghum, soybean, and vegetables, this particular strain of FAW seems to be a bit more selective. Several people have reported FAW only eating the fescue grass and leaving behind crabgrass and other plants and weeds. Kentucky bluegrass, and Zoysiagrass for example have not appeared to have been damaged. There have also been very few reports of FAW in late-planted sweet corn, which is often a magnet for FAW. So, we are not sure exactly what crops might be at risk from this current strain of FAW. We are advising to keep a close watch on all susceptible host plants.
3. Does climate change play a role in spreading armyworms? If so, how? Fall armyworms are tropical moths. They cannot survive cold winters. With climate change, it is possible that these moths are overwintering a little further north than usual. If climate change leads to dry (drought) conditions in the southern states, then high densities of these moths can build up. When storm winds blow north, they carry the moths to the mid-Atlantic, northeast, and Midwestern states.
4. What do you think the rest of the year will look like in terms of armyworms? Is the worst behind us or yet to come? Great question. The fall armyworm will complete a full generation of its life cycle (egg-larvae-pupa-adult moth) in about 30-40 days, depending on weather conditions. This fall armyworm outbreak occurred early enough for the moth population to still cycle through another generation here in Virginia, meaning more eggs might be deposited on lawns and more devastation from larval feeding may occur. However, FAW are very susceptible to disease that occurs after wet rainy conditions, which we’ve also experienced. So, we may see things go either direction. Still don’t know.
5. Have there been previous years where we’ve seen a similar explosion in army worms? Is this going to be the ‘new normal’ having FAW every year?
We last had a fall armyworm outbreak in 2018. It was not as severe. This is the worst FAW devastation that I’ve seen in Virginia in my 30-year career in entomology. We still do not know if we might have another huge outbreak of FAW in 2022. All we know that some insect pests have cycles between outbreak. It could be possible that with warmer and dryer conditions, we might see FAW being present in higher number during the upcoming years. Now we know that this creature can come in Virginia as early as late-August. Scouting for this pest will be still crucial.
6. What can you do about them?
If lawns have been killed, the only recourse is to reseed the lawn this fall. If new fall cover crop plantings have been devoured, then reseeding those also may be the only recourse. For crop protection, insecticides recommended for control include most pyrethroids (active ingredients such as bifenthrin [in the products Talstar, Brigade, Sniper, and many others]), lambda-cyhalothrin, and commercial products such as Mustang Max, Baythroid XL, and others), the carbamate, Lannate LV, and many of the more selective (lepidopteran-targeting) insecticides such as the diamides Prevathon, Coragen, Acelepryn, Besiege, indoxacarb products like Steward, Avaunt eVo, Provaunt, the active ingredient spinosad (in products such as Blackhawk, Tracer, Matchpoint), and other products including Radiant, or Intrepid Edge. Consult the relevant Pest management Guide for specific recommendations on the various commodities. Please note that control of large larvae may be difficult with any insecticide. Link to the VCE Pest Management Guides for Field Crops, Vegetables, and Turf are provided below. On turf, we have gotten very good control of FAW larvae with pyrethroids, which are also one cheaper insecticide options. Golf course turf treated with a systemic diamide insecticide like Acelepryn or Tetrino have shown no damage even after 50 days post-spray.
By: Drs. Tom Kuhar, Alejandro Del Pozo, and Sally Taylor (Dept. of Entomology, Virginia Tech)
Recently, some VCE agents as well as golf course superintendents in the northcentral and southwestern counties of Virginia have reported fall armyworm outbreaks (Fig. 1) on lawns and golf courses. This outbreak is earlier than usual and potentially could lead to one of the heaviest pest problems that we’ve experienced from this pest in Virginia in recent years. Some lawns have completely been destroyed by these voracious feeders (Fig. 2 and 3).
Fig. 1. Fall armyworm larvae collected from a lawn in Richmond, VA. August 26, 2021. Photo courtesy of Jeff Sacks.
Fig. 2. Fall armyworm destroyed lawn in Henrico Co. August 26, 2021. Photo courtesy of Jeff Sacks.
Fig. 3. FAW damage to lawn in Richmond, VA. August 26, 2021. Photo courtesy of Tyler Green.
It’s important to understand the biology of this polyphagus pest (Fig. 4). Fall armyworm (Spodoptera frugiperda) is a tropical moth native to warm climate areas of the western hemisphere. It cannot successfully overwinter in Virginia. However, fall armyworm moths (see Fig. 9) are strong fliers, and populations can show up throughout the eastern United States in the late summer and fall months, sometimes in very high populations like we saw most recently in 2018 in Virginia, and now in 2021. Female FAW moths can lay up to 10 egg masses (each with 100 – 200 eggs) (see Fig 4). So, huge densities of armyworms can build up from just a few egg laying moths in a field. This can completely destroy lawns or new plantings of grain cover crops.
Fig. 4. Biology of the fall armyworm. Photos courtesy of *cripts.farmradio.fm/radio-resource-packs/107-farm-radio-resource-pack/backgrounder-fall-armyworm/
Fall armyworm can feed on a number of different host plants, but prefers grasses, small grains, corn, and sorghum.
Control
Insecticides recommended for control include most pyrethroids (such as bifenthrin, lambda-cyhalothrin, as active ingredients, and some commercial formulations such as Mustang Max, Baythroid XL, etc.), the carbamate (Lannate LV) and many of the more selective (lepidopteran-targeting) insecticides such as the diamide Prevathon, Coragen, Acelepryn, Besiege (as commercial formulations), indoxacarb products like Steward, Avaunt eVo, Provaunt, spinosad products such as Blackhawk, Tracer, Matchpoint, and additional insecticides such as Radiant, Intrepid Edge, as well others. Consult the relevant Pest management Guide for specific recommendations on the various commodities. Please note that control of large larvae is sometimes difficult with any insecticide. Link to the VCE Pest Management Guides for Field Crops, Vegetables, and Turf are provided below. On turf, we have gotten very good control of FAW larvae with pyrethroids, which are also one the cheaper insecticide options.
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.
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.
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.
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:
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.
Over the past couple of weeks our fruiting vegetable crops at Kentland Farm in Whitethorne, Virginia have been invaded by abundant numbers of leaf-footed bugs (Leptoglossus spp.). These bugs that are in the same bug family Coreidae as the squash bug Anasa tristus. They are piercing sucking feeders that have killed entire cucumber and zucchini plants from their feeding on stems and leaves or have caused numerous puncture wounds on fruit, which result in a little fluid oozing from the fruit.
Leaf-footed bug adults and nymphs on zucchini. Photo by Courtney Walls, Virginia Tech Entomology Graduate Student.
These insect pests can be controlled using the same insecticides that are labeled for use on stink bugs and squash bugs, namely, pyrethroids or neonicotinoids for conventional growers. Organic growers can achieve some suppression of bugs with the use of products containing pyrethrins such as Pyganic or Azera, or with the use of Surround (kaolin clay powder), which also works to prevent sunscald on fruit.
Since early July, we have been monitoring Heliothis traps baited with corn earworm pheromone at on 4 hemp fields and one sweet corn field in and around Montgomery, Co., Virginia. Below are the trap catch results. After a week or two of low catch, the moth activity has picked up especially at the Wall sweet corn.
FMC Corp. just released a new insecticide Elevest WITH RYNAXYPYR® ACTIVE and BIFENTHRIN. This new insecticide should be available in late season 2020. According to the label, Elevest is registered for use on corn, soybean, edible bean, sweet corn, peanut, cotton, potato and a few other crops. Similar to the product Besiege, Elevest is a mixture of a Group 3A pyrethroid (bifenthrin) with the diamide Group 28 insecticide chlorantraniliprole, which is found in the popular products Coragen or Prevathon. Thus, it will be effective on a wide range of insect pests.
By: Tom Kuhar (Entomology Professor, Virginia Tech), Kadie Britt (Ph.D. student researching hemp IPM), and Helene Doughty (Entomologist, Eastern Shore AREC, Painter, VA)
Fig. 1. Corn earworm damaging CBD hemp in Virginia. Photo by Kadie Britt.
Corn earworm can be quite damaging to the seed heads of hemp grown for grain (Fig. 2), but, as we’ve seen recently in Virginia, the pest can also damage hemp grown for CBD oil. Over the past few weeks, corn earworm densities and damage to CBD hemp has reached very high levels throughout Virginia, and their presence in fields has been associated with increased flower bud rot (Fig. 3). This can result in significant economic damage to that crop.
Due to strict regulations on pesticide use on hemp, insecticide
recommendations for managing this pest are quite limited at this time. Recently, we evaluated the efficacy of some naturally-derived
pesticides that can be legally applied on hemp in Virginia and one
naturally-derived (OMRI-certified) insecticide that currently is not allowed to
be applied on hemp (Spinosad).
Fig. 1. Corn earworm damage to grain hemp. Photo by Helene Doughty, Eastern Shore AREC. Fig. 2. Bud rot on CBD hemp. Photo by Kadie Britt.
Gemstar (5 fl oz/A) – which is a nuclear polyhedrosis virus that is specific to the corn earworm species. The virus causes corn earworm to become sick and die. Fig. 4. Shows a corn earworm killed by the virus.
Javelin WG (8 oz/A) – Bacillus thuringiensis (Bt) strain kurstaki – bacterial crystalline proteins that kill caterpillars.
Dipel DF (16 oz/A) – Bt kurstaki different formulation
Entrust (5 oz/A) – Spinosad derived from soil microbes. *cannot legally be applied on hemp in Virginia.
Fig. 4. Corn earworm killed by virus (Gemstar insecticide). ESAREC 2019. Photo by Helene Doughty.
We evaluated their efficacy in the field on the Eastern Shore of Virginia in a randomized complete block small plot trial. Hemp plots were sprayed twice (1 week apart) and numbers of live CEW larvae and damage was assessed. Results are shown in Figs. 5 & 6. Entrust was the only product that provided effective control of CEW. Unfortunately, this is the one product that we evaluated that is not allowed to be applied on hemp. The insecticide Entrust is OMRI-certified however.
Fig. 5. Numbers of live corn earworm larvae on hemp plants after insecticide treatments at the ESAREC, Painter, VA.Fig. 6 Corn earworm damage to hemp seeds in the field after insecticide treatments.
Virginia Tech
bioassay trial:
Treatments included:
Gemstar (5 fl oz/A) – which is a
nuclear polyhedrosis virus that is specific to the corn earworm species. The virus causes corn earworm to become sick
and die. Fig. 3. Shows a corn earworm
killed by the virus.
Javelin WG (8 oz/A) – Bacillus thuringiensis (Bt) strain kurstaki – bacterial crystalline proteins that kill caterpillars.
Dipel DF (16 oz/A) – Bt kurstaki
different formulation
Entrust (5 oz/A) – Spinosad derived
from soil microbes. *cannot legally be
applied on hemp in Virginia.
In order to evaluate the efficacy, untreated hemp seed heads were collected from Kentland Farm and dipped in each of the treatments. Approximately 1 oz of seeds was placed per diet cup and four reps of 10 cups each were set up for the aforementioned six insecticide treatments. CEW larvae (3rd instar (medium sized) were collected from sweet corn planted at Kentland Farm and were immediately placed 1 larva per cup. Mortality was evaluated 1, 2, 3, and 4 days after treatment (Fig. 7). Similar to the Eastern shore field trial, Entrust provided the most effective control of CEW. However, this trial also included the Bt aizawai product Xentari, which also provided significant control (better than the other products except spinosad. Xentari is allowed for use on hemp in Virginia. For best management of corn earworm during this time, apply Bt products on hemp every few (2-3) days in early morning or late evening. Corn earworm must consume the insecticide for the application to be effective, so ensure good spray coverage on plants. Dead worms may not be noticed until 48 hours after first application.
Fig. 7. Percentage mortality of corn earworm larvae placed on treated hemp seeds in a controlled laboratory experiment. DAT refers to days after treatment (insecticide dip).
