Written by Brian Currin (Entomology Graduate Student at Virginia Tech). Brian is working on sweet corn IPM for his research. Corn earworm monitoring is continuing in Virginia. As we grow nearer to the time corn begins to silk, and when corn earworm moths lay their eggs, monitoring is important for integrated pest management strategies.
Trap catch for this week ending July 20 at two locations was as follows:
Clover, VA (Data collected by Bill Tiver) 77 moths per wk (high pressure) Blacksburg, VA (Data collected by Brian Currin) only 2 moths (very low pressure)
The farm in Blacksburg has yet to reach its reproductive stage but during trap monitoring more adults were seen flying in the corn.
Mid-July is that time of year when we begin to see corn earworm moth activity really pick up in Virginia. As most of us know, corn earworm moths deposit their eggs on flowering plants of many important agricultural crops including sweet corn, cotton, soybean, and hemp, to name a few. Eggs hatch in a couple days into larvae that feed on buds, flowers, fruit, and leaves. Pheromone trap counts of 7 or more CEW moths per week indicates that this pest is active on the farm and could potentially become a pest threat.
Trap catch for this week ending July 14 at several locations is as follows:
Corn Earworm Trap Location
moths per wk
Location
6/9
6/15
6/22
6/29
7/6
7/13
Townsend
46
7
3
4
19
3
Cheriton
1
2
2
0
0
1
Machipongo
4
1
0
0
2
1
Nassawadox
3
3
4
0
1
0
Chatham
40
50
55
Blacksburg
2
10
8
Corn earworm moth catch in Heliothis mesh traps baited with pheromone lures at 6 locations in Virginia.
In summary, CEW moth activity has subsided on the Eastern Shore for the time being as the pest is likely mostly in the larval stage right now. In Chatham (southside VA) CEW moth activity has remained high >50 moths per week. Blacksburg, VA has experienced only low moth numbers so far.
Thank you to Helene Doughty who is monitoring the traps on the Eastern Shore, Bill Tiver who is monitoring a trap in Clover, VA, and Brian Currin who is monitoring traps around Blacksburg.
This article was written by Jordan Thompson, a graduate student in the Department of Entomology working with Drs. Tom Kuhar and Alejandro Del Pozo. Jordan is a graduate student at Virginia Tech studying the Asian jumping worm in Virginia and hoping to find possible control methods. Jordant95@vt.edu
Earthworms might not be the first thing that comes to mind when thinking about invasive species. In fact, you might be familiar with all the benefits of earthworms, such as how they recycle nutrients by breaking down organic matter, making them more available to plants, or how they tunnel through the soil, aerating it, which in turn makes room for delicate plant roots to spread. You may have even purchased a bag of worm castings to spread in your garden, or perhaps you compost with red wigglers. Whatever your association with earthworms, the thought of eradicating them probably didn’t immediately come to mind.
Unfortunately, we now have a worm in the United States that is detrimental to our delicate soil ecosystems. Known as the Asian jumping worm (Amynthas spp.), this invasive earthworm is named for its signature jumping move, a form of predator evasion. They are characterized by their smooth iridescent skin, and their pale clitellum (band). The Asian jumping worm is able to quickly reshape invaded soil ecosystems, resulting in soil that offers minimal benefits to plants and other terrestrial organisms. Where there was once a rich organic matter layer, is now a dusty and lifeless earth, incapable of supporting certain plant life, thereby permanently altering the landscape and inviting other invasive species to move in and thrive. It is evident that these worms are far from being the allies we seek in maintaining a healthy ecosystem.
But how did they get here? Why does it do so well in so many diverse soils? What are the long-term effects of this species? Let’s break it down.
The Asian Jumping Worm: An Uninvited Guest
The Asian jumping worm originally hails from East Asia and is believed to have been introduced to other regions through various pathways, including horticultural trade, transportation of plants, and contaminated soil or plant material. One key factor contributing to the Asian jumping worm’s rapid spread is its ability to reproduce via parthenogenesis, meaning it can reproduce without a mate. Each worm produces tiny cocoons at around 60 days of age, and each cocoon will hold between 2 and 20 worms – which will again start producing more cocoons in about 60 days. This allows for about 2 generations per year. Often in a soil rich in organic matter, it is not unusual to find hundreds of worms living within an area of a few square feet. The juveniles are almost microscopic, resembling tiny white threads. The cocoons are the size of a mustard seed, and could easily be picked up by animals and humans walking through worm infested soil.
Additionally, the Asian jumping worm’s adaptability to different soil types is another reason for its success as an invasive species. Although it seems to prefer organic matter rich soils, it can thrive in a wide range of soil conditions, even in sandy or clayey soils. Moreover, unlike other earthworms which tend to stay within certain soil layers, Asian jumping worms are more surface-dwelling, making them highly mobile and able to colonize new areas rapidly.
Their ability to survive in colder climates also contributes to their successful spread. Adults will die with the first frost, but leave behind specialized cocoons that protect their eggs and developing juveniles during winter months. This enables them to establish populations in regions that experience cold winters.
In 2022, Asian jumping worms had been confirmed in a handful of counties in Virginia, but a bit of citizen science with the help of Facebook confirms their presence is being severely under-reported or simply, they’ve been surviving unnoticed, and have likely spread well beyond the original counties.
Disturbing the Ground: Impacts on Soil Ecosystems
Asian jumping worms have a voracious appetite for organic matter. They consume leaf litter, mulch, and other organic debris at an accelerated rate, rapidly depleting the available organic material in the soil. This feeding behavior disrupts the soil structure and leaves soil vulnerable to runoff, in addition to reducing the plant life capable of growing there. This specifically affects forest understories, where small trees and shrubs are essential in providing groundcover, soil stability, and forage for wildlife. When Asian jumping worms invade, it can alter the understory therefore altering the native habitat and displacing wildlife and native plant communities.
In residential areas, avid backyard vegetable growers might notice their gardens becoming less prolific. Their plants might begin to struggle and eventually they may see bare spots where once there were lush gardens. Compost piles can become breeding grounds as banana peels and grass clippings become fuel for more generations of jumping worms. In large turf areas such as golf courses, where worm castings already present an issue with aesthetics and maintenance, worms that altogether destroy the soil could spell disaster for ranges trying to maintain quality greens.
There is some understanding of how these worms alter soil chemistry, C/N (carbon to nitrogen) ratios, and soil electrical conductivity, but more research is needed to better understand the severity of these alterations and their long term effects. What we do know is that while soil development takes thousands of years, the Asian jumping worm can significantly alter soil composition in a matter of months. This poses a grave concern and demands our immediate attention.
Current Research and Areas of Study
Researchers from Virginia Tech’s Department of Entomology are actively studying the impacts of the Asian jumping worm in Virginia and exploring potential control methods. Through field observations and laboratory experiments, they are investigating the effects of Asian jumping worms on other soil arthropods, soil nutrient availability, soil electrical conductivity, and more. By understanding the mechanisms through which these worms degrade the soil, researchers aim to develop targeted management strategies. These may include exploring biological control agents, evaluating cultural practices, and assessing the efficacy of chemical interventions.
Current Research and Areas of Study
Researchers from Virginia Tech’s Department of Entomology are actively studying the impacts of the Asian jumping worm in Virginia and exploring potential control methods. Through field observations and laboratory experiments, they are investigating the effects of Asian jumping worms on other soil arthropods, soil nutrient availability, soil electrical conductivity, and more. By understanding the mechanisms through which these worms degrade the soil, researchers aim to develop targeted management strategies. These may include exploring biological control agents, evaluating cultural practices, and assessing the efficacy of chemical interventions.
We know that we aren’t the only ones, but we are monitoring corn earworm moths again in Virginia at multiple locations. Pheromone trap counts of 7 or more moths per week indicates that this pest is active on the farm and could potentially become a pest threat to the numerous crops that it attacks such as sweet corn, cotton, hemp, soybean, tomato, and many others. Female egg-laying moths are particularly attracted to flowering plants or plants with fruiting stages.
Trap catch for this week ending June 29 at several locations is as follows:
Townsend (Eastern Shore) – 4 moths
Cheriton (Eastern Shore) – 0
Machipongo (Eastern Shore) – 0
Nassawadox (Eastern Shore) – 0
Clover (Southside VA) – 66 moths
Blacksburg (southwest ridge and valley) – 2 moths
Thank you to Helene Doughty who is monitoring the traps on the Eastern Shore, Bill Tiver who is monitoring a trap in Clover, VA, and Brian Currin who is monitoring traps around Blacksburg. Moth catch was low on the Eastern Shore and in Blacksburg this week, but rather high at the Clover site; however, sweet corn is in reproductive stages on that farm and probably a very attractive location in southside, VA.
Everyone is gearing up and planning for potato planting to begin soon! With two primary insect pests of great economic importance: Colorado potato beetles and wireworms, growers are sometimes perplexed on what the best option may be or looking for that new product that will solve all their insect problems.
COLORADO POTATO BEETLES: No new products have been registered for Colorado potato beetle control for 2023. However, at-planting neonicotinoid insecticides are still working well in our area (thankfully!). Field trials at the ESAREC in 2021 comparing labeled at-planting insecticides yielded great results for Colorado potato beetle control, up to 56 DAP (Figure 1 and 2). Similar residual efficacy has been shown on commercial farms on the Shore as well based on previous assays from 2021.
And for those pesky beetles infesting fields later in the season (likely from neighboring potato fields from the previous year) once the at-planting insecticide has worn off, there are still numerous options for foliar control (being mindful to rotate to a foliar insecticide in a different IRAC group) (Figure 3). A couple new insecticides with new mode of actions should be available later in 2023 or 2024, which have performed very well in our CPB efficacy trials; these include plinazolin a new Group 30 mode of action, and Calantha (a new RNAi insecticide that is highly specific to CPB and not toxic to any other organisms).
WIREWORMS:
Questions about wireworm control come back every year. With recurring problematic fields, growers are always in search of new options. Based on 15 years of research at the ESAREC, the combination of Regent (fipronil) with a neonicotinoid (thiamethoxam or imidacloprid) at planting still offers the best control for seedpiece protection. A new option is available in 2023 with a group 30 insecticide, broflanilide, currently marketed under the trade name Nurizma. We are looking forward to testing it as an at-planting insecticide in our potato field trials in the upcoming season. We are also interested in assessing the wireworm suppression ability of this same insecticide applied as a seed treatment to wheat cover crops. Research has shown that this can significantly reduce wireworm populations in a field for subsequent crops like potato.
More research work in the upcoming years will continue to focus on understanding the biology of this pest in its larval and adult stage as well as reduction of wireworm population in fields for potato production through seed treatments in rotational crops.
This week I visited several vegetable farms in southside (southcentral) Virginia and found beet armyworm infestations at all of the farms. This is not good news as this insect pest can be difficult to control. One field of Brussels sprouts had been sprayed with a pyrethroid and with Lannate the spray before and had a healthy population of beet armyworms doing a lot of damage (see photo). I saw mostly young larvae and even some egg masses (see photo). Based on my experience, this pest is resistant to those two classes of insecticides.
History and Pest Status of the Beet Armyworm in the U.S.
The beet armyworm (BAW) is a widely distributed polyphagous insect pest of >90 species of plants and cultivated crops, including alfalfa, asparagus, bean, beet, broccoli, cabbage, cauliflower, celery, chickpea, corn, cotton, cowpea, eggplant, lettuce, onion, pea, peanut, pepper, potato, radish, safflower, sorghum, soybean, spinach, sugarbeet, sweetpotato, tobacco, tomato, and turnip. The insect also feeds on fruit and ornamental plants. The BAW is native to Southeast Asia, but has spread throughout much of the world. It was first discovered in North America in the late 1800’s on the west coast, and reached the southeastern U.S. by the 1920’s. As it is a tropical insect, it lacks a diapause and ability to overwinter in colder (temperate) climates. High populations of BAW occur in the southeastern and southwestern states in the spring, and highly mobile migrants usually make their way northward each summer to the Mid-Atlantic states, Colorado, and northern California. Occasionally the pest is found as far north as New York and even Canada.
Damage
BAW larvae feed on foliage and fruit. When they are young, larvae feed gregariously, usually in great numbers, where they skeletonize and web leaves. As they mature, larvae devour more foliage and may burrow into fruit or heads of plants. When BAW outbreaks occur in a region, they are conspicuous and often become the primary pest control focus of growers of numerous field and vegetable crops because of the sheer numbers of larvae and their ability to move from crop to crop. If they are not controlled, BAW infestations can sometimes result in total crop losses. The insects have a high reproductive potential; eggs are laid in clusters of 50 to 150 eggs, and female moths can produce over 1300 eggs in a lifetime. In addition, eggs are well protected from the environment and predators because they are usually deposited on the undersides of leaves and are covered with cottony scales deposited by the female moth. This usually results in numerous larvae infesting a single plant after egg hatch.
Insecticide Resistance in the Beet Armyworm
BAW has a high propensity for developing resistance to insecticides. In the southeast and southwestern states, the relatively high abundance of BAW coupled with large acreages of valuable crops has stimulated a long history of intense insecticide use . Not surprisingly, this has resulted in the development of resistance to a diverse array of pesticide classes, including chlorinated hydrocarbons, organophosphates, carbamates, pyrethroids, and benzoylphenylureas. Some recommended insecticide options include the diamides such as Coragen, Harvanta, Beseige, Elevest, etc.., spinosyns like Radiant or Blackhawk or Entrust for organic growers. Bt products like Dipel, Agree, Xentari, Javelin, Deliver, etc.. will provide very good control of small larvae. Proclaim and Avaunt are also effective products from past efficacy trials.
By Kelly McIntyre1, Helene Doughty2, Lorena Lopez2, and Tom Kuhar1
This summer and fall, we are tracking moth flight numbers around Virginia using pheromone traps for three important pests, fall armyworm (FAW), which can attack most grasses, corn, sorghum, small grains, and even alfalfa; pickleworm, which is a late season pest of squash, pumpkins, and cucumbers, and corn earworm (CEW), which attacks over 300 host plants including many of the major crops in Virginia. FAW and pickleworm do not overwinter in Virginia and typically are carried northward in late summer on storm fronts coming from the south.
Researchers have demonstrated that certain trap types are better for certain moth species. We are monitoring fall armyworm moths using the bucket trap baited with a Trece FAW pheromone lure and placed near corn fields. We are monitoring the presence of pickleworm moths using the Trece Deltatrap baited with the pheromone lure and placed around pumpkin fields. Corn earworm is monitored using the Heliothis mesh trap or the Hartstack wire mesh trap, which catches the most corn earworm moths among all trap types.
FW = fall armyworm; PW= pickleworm; CEW = Corn Earworm
By Kyle Bekelja (postdoc), Tom Kuhar (Professor), and Sally Taylor (Associate Professor) Department of Entomology, Virginia Tech
We installed our pheromone bucket traps for fall armyworm in late July at Homefield Farm in Whitethorne, VA and we caught moths the first week (8 per trap). This alerted us that this tropical moth pest had already reached southwest Virginia. Then, this week, August 16, 2022, we noticed a pretty bad infestation of FAW larvae in our sweet corn at this same location.
The Pest. Fall armyworm (FAW) is a moth pest that migrates northward during late summer and early fall. Be on the lookout for this pest especially during times of northerly winds (such as tropical storms) which can carry female moths to Virginia late in the season. Fall armyworms have a wider host range that includes more than 80 plants: vegetables include sweet corn, tomatoes, and peppers, field and forage crops such as alfalfa, cotton, and peanuts, and ornamental commodities, especially turfgrass. Last year, FAW hit turfgrass hard in Virginia; this year, we have already started seeing it in sweet corn. Based on observations from Dr. Scott Stewart in Tennessee, we believe that this strain of FAW favors corn and is likely not going to be a huge turf pest like we saw in fall 2021.
Identification
Be on the lookout for shotgun-patterned damage and lots of frass (i.e., poop) in the corn whorl, shown in Figure 1 (we noticed feeding that was concentrated on un-emerged tassels). If you dig deep inside the whorl, you’re likely to find a caterpillar with the telltale inverted “Y” on its forehead, and four black dots at the tail-end of the abdomen, shown in Figure 2.
Treatment Evaluation. We collected FAW caterpillars from sweet corn at Homefield Farm in Blacksburg, VA on August 16, 2022, and assessed percent mortality using treatments listed in Table 1. We placed caterpillars in 1-ounce cups with corn tassels that were dipped into solutions of treatments, and assessed mortality after 24-hours. All treatments provided good control compared to a water check. Although the pyrethroid lambda-cyhalothrin resulted in over 83% mortality of FAW, the two products that combine the diamide chlorantraniliprole with pyrethroids (Beseige and Elevest) resulted in 100% mortality after 24 hours.
Insecticide bioassay Results of field-collected fall armyworm larvae.
Control. Insecticides recommended for controlling FAW include pyrethroids (such as Lambda-Cyhalothrin, bifenthrin, and others) and more selective caterpillar-targeting insecticides such as Prevathon, Coragen, and Acelepryn. Consider using some of these more selective options during times when pollinators are more active (e.g., while sweet corn is tasseling). Consult the relevant pest management guides for specific recommendations on various commodities. Remember that control of large caterpillars is often difficult with any insecticide.
In southwest Virginia we’ve seen a lot of squash vine borer problems this summer. More than usual. This moth pest lays its eggs (singly) at the base of squash or pumpkins, where the larva quickly bores into the plant after egg hatch and ultimately kills the vine or entire plant (as we’ve seen in our squash research plots in Whitethorne, VA).
Control
Squash vine borer can be a major pest challenge for growers and home gardeners. If you only have a few plants to protect, then trying to cover the base of plants with aluminum foil or the cardboard can help as the moth prefers to deposit the egg at the base of plants. This acts as an oviposition deterrent. However, this is not practical for commercial growers and the best control option is an insecticide spray directed at the base of plants where the female moth may contact it and die before laying the egg, or, after egg hatch, the young neonate larvae may die from the insecticide residue before boring into the plant, where it will be protected. Pyrethroids such as Asana XL (esfenvalerate), Baythroid XL (beta-cyfluthrin), Brigade 2EC (bifenthrin), Danitol 2.4EC (fenpropathrin), Hero EW (zeta-cypermethrin + bifenthrin), Warrior II or Lambda-Cy 1EC (lambda-cyhalothrin), Mustang Maxx (zeta-cypermethrin), Permethrin 3.2EC, Tombstone (cyfluthrin), to name a few, are the most effective insecticides for quick contact control of the SVB. As always, please read the label before using any insecticide and be mindful that pyrethroids are toxic to pollinators and other beneficial arthropods. So avoiding spraying when flowers are open and in bloom, and directing sprays to the base of plants will help reduce nontarget impacts.
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.
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