Corn earworm report for September 8, 2022

Corn earworm (=bollworm) moth captures from southeast Virginia black light traps this week were 5 per night at Templeton (Prince George Co.) and 4 per night at Disputanta (Prince George Co.); Suffolk numbers averaged 45 per night. Here is the Table. In our pyrethroid resistance monitoring tests, the seasonal average is at 33% survival (n=565 moths tested).

Beet armyworm infestations in central Virginia

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.

Beet armyworm on Brussels sprouts in southside Virginia. September 2022.

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

Beet armyworm egg mass.

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.

Insecticides for Controlling Late-Season Pests of Cucurbits, Plus an Insecticide Evaluation

By: Kyle Bekelja, Kelly McIntyre, and Thomas Kuhar

Figure 1. Striped and spotted cucumber beetles feeding on a pie pumpkin (Image credit: Thomas Kuhar)

Insecticides
It’s late in the growing season, which means many cucurbit growers, especially those growing pumpkins, need to start thinking about how they’re going to keep their fruit looking pretty for the coming weeks! Table 1 shows a list of insecticides and their effectiveness against a few key pests of cucurbits based on insecticide evaluations, their preharvest-intervals (PHI), and their relative bee toxicity rating (i.e., high, medium, low).

Table 1. Insecticides for managing key pests of cucurbits. Effectiveness rating scale: E = excellent; G = good; F = Fair; P = poor (credit: Thomas Kuhar)

Insecticide Evaluation
In the lab, we tested Assail 30SG at four rates (0.44, 0.88, 1.75, and 2.50 dry oz/acre) for its effectiveness against cucumber beetles. We looked at percent mortality and percent damaged leaves for each treatment.

Figure 2. Bar graph showing percent mortality of cucumber beetles at 2, 3, and 4 days after treatment (DAT).

Although the percent mortality was relatively low for Assail at the 1.75 rate, as shown in Figure 2, it still seemed to have prevented beetles from feeding on plant material, shown in Figure 3.

Figure 3. Bar graph showing percent damaged leaves at 2, 3, and 4 days after treatment (DAT) with insecticides targeting cucumber beetles.

Assail 30SG prevented cucumber beetle feeding, and outperformed Bifenture DF four days after treatments were applied at the 1.75 and 2.50 rate (Figure 3). Although % mortality was low at the 1.75 rate (Figure 2), it appears that feeding was still prevented.

Assail 30SG has the added benefit of being less toxic to bees than many other options, and has a short preharvest interval. Regardless of your chemistry, try to avoid spraying while pollinators are active!

Monitoring Fall armyworm – 1 September 2022

By: Kelly McIntyre and Thomas Kuhar

This week FAW adults were observed at 5 of 20 monitoring locations throughout the state. The West Central region (Carroll and Montgomery counties) had greater counts (5-63 individuals) though adults were also observed (1 individual) in Central Virginia (Henrico and Hanover counties). See table for all locations and counts.


Corn earworm update for September 1, 2022

Corn earworm (=bollworm) moth captures from southeast Virginia black light traps this week were 7 per night at Templeton (Prince George Co.) and 9 per night at Disputanta (Prince George Co.); Suffolk numbers reached 60 per night. Here is the Table. In our pyrethroid resistance monitoring tests, the seasonal average is at 33% survival (n=502 moths tested).

Monitoring Fall armyworm – Week of August 25, 2022

By: Kelly McIntyre and Thomas Kuhar

This week FAW adults were observed at 5 of 15 monitoring locations throughout the state. Western regions (Carroll and Montgomery counties) of the state had greater counts (4-26 individuals) though adults were also observed (1 individual) in eastern Virginia (Williamsburg and Northampton County). See table for all locations and counts.

Monitoring Pickleworm and Melonworm – Week of August 25, 2022

By Lorena Lopez, Kelly McIntyre, and Tom Kuhar

Last year, we at Virginia Tech started a pickleworm and melonworm monitoring program consisting of information exchange between cucurbit growers and extension agents across the state that looked for these pests’ damage to cucurbit blossoms or fruits. In 2021, we recorded up to 80% of squash fruits or flower buds infested with either pickleworms or melonworms. This year we continued with the monitoring efforts by monitoring closely summer squash fields in the Eastern Shore, Blacksburg, and Chesapeake area and no pickleworms nor melonworms have been detected.

Additionally, we set up traps with pickleworm pheromone lures in squash and pumpkin fields in Montross, Hillsville, Cape Charles, Painter, Hampton Roads, and Madison County. If these moths are present in the area, they will be attracted to the lure at night when they are active. After two weeks of trapping, no pickleworms or melonworms have been caught in the traps. We will continue to trap these pests as the summer squash season finishes and the pumpkin season continues and will keep you updated.

Pickleworm larva

Pickleworm adult

Corn earworm/bollworm update for August 25, 2022

This week’s corn earworm (=bollworm) moth captures from local black light traps were: Sara Rutherford (Greensville ANR Agent) reported a nightly average of 20 moths; Scott Reiter (Prince George ANR Agent) had 8 per night at Templeton and 10 at Disputanta; the Spiers reported 5 per night in Dinwiddie; and we averaged 28 in Suffolk. Here is the Table. In our pyrethroid resistance monitoring tests, the seasonal average is at 30% survival (n=395 moths tested).

Monitoring Fall armyworm, Pickleworm, and Corn Earworm in Virginia – Week of August 19

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. 

Fall armyworms.
Fall armyworm moth
pickleworm damage
pickleworm moth.
corn earworm
corn earworm moth

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. 

Phil Blevins, Washington County VCE Agent – ANR, standing in front of his Bt sweet corn trial adjacent to a Heliothis trap for corn earworm and a bucket trap for fall armyworm monitoring.
FW = fall armyworm; PW= pickleworm; CEW = Corn Earworm
namelocationdate checked# days since last check# FAW (if applicable)# PW (if applicable)# CEW (if applicable)
McintyreHomefield Farm – Whitethorne8/96905
McintyreWall Farm – Blacksburg8/96nana109
McintyreTurfgrass Center – Blacksburg8/96300
McintyreHomefield Farm – Whitethorne8/1781100
McintyreWall Farm – Blacksburg8/178nana
McintyreTurfgrass Center – Blacksburg8/178400
McintyreHomefield Farm – Whitethorne
McintyreWall Farm – Blacksburg
McintyreTurfgrass Center – Blacksburg
DoughtyESAREC, Painter, VA6/157nana30
DoughtyESAREC, Painter, VA6/227nana8
DoughtyESAREC, Painter, VA6/297nana7
DoughtyESAREC, Painter, VA7/67nana24
DoughtyESAREC, Painter, VA7/137nana5
DoughtyESAREC, Painter, VA7/2070na18
DoughtyESAREC, Painter, VA7/2770na39
DoughtyESAREC, Painter, VA8/372na19
DoughtyESAREC, Painter, VA8/129
DoughtyESAREC, Painter, VA8/175155
RomelczykMontross8/1240
RomelczykMontross8-1790
LopezESAREC, Painter, VA8/187na0na
FlanaganCullipher Farms, VB, VA8/18N/A340
LopezHRAREC8/187na0na
LopezSea Breeze Farm, Cape Charles8/187na042
DeitchArlington RD – Northampton Co.8/27na8
DeitchSeaview – Northampton Co.8/27na246
DeitchMachipongo – Northampton Co.8/27na43
DeitchNassawadox – Northampton Co.8/270na
DeitchTownsend – Northampton Co.8/270na
DeitchKendall Grove – Northampton Co.8/270na
DeitchRed Bank Road – Northampton Co.8/270na
DeitchExmore – Northampton Co.8/270na
DeitchArlington RD – Northampton Co.8/97na25
DeitchSeaview – Northampton Co.8/97na3
DeitchMachipongo – Northampton Co.8/97na66
DeitchNassawadox – Northampton Co.8/97na8
DeitchTownsend – Northampton Co.8/970na
DeitchKendall Grove – Northampton Co.8/971na
DeitchRed Bank Road – Northampton Co.8/970na
DeitchExmore – Northampton Co.8/970na
DeitchArlington RD – Northampton Co.8/167na16
DeitchSeaview – Northampton Co.8/167na4
DeitchMachipongo – Northampton Co.8/167na168
DeitchNassawadox – Northampton Co.8/167na4
DeitchTownsend – Northampton Co.8/1671na
DeitchKendall Grove – Northampton Co.8/1670na
DeitchRed Bank Road – Northampton Co.8/1670na
DeitchExmore – Northampton Co.8/1670na

Fall armyworm in southwest Virginia sweet corn – treatment evaluation and recommendations

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. 

Fig. 1. Fall armyworm in sweet corn at Homefield Farm, Whitethorne, VA, August 15, 2022.

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.

Figure 2. Image credit: Department of Entomology, University of Nebraska-Lincoln

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.

Fig 3. Table Showing Fall Armyworm Larval Mortality After 24-hours exposure to treated corn tassel (conducted Aug 17, 2022, Whitethorne, VA).

 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.