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.

1.  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.  

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. 

Links to Pest Management Guides   https://resources.ext.vt.edu/

Turf:  

https://resources.ext.vt.edu/contentdetail?contentid=2377&contentname=2021%20Pest%20Management%20Guide%20-%20Home%20Grounds%20and%20Animals

Field Crops:      

https://resources.ext.vt.edu/contentdetail?contentid=2375&contentname=2021%20Pest%20Management%20Guide%20-%20Field%20Crops

Vegetables:  

https://resources.ext.vt.edu/contentdetail?contentid=2379&contentname=2020-2021%20Mid-Atlantic%20Commercial%20Vegetable%20Production%20Recommendations

Increased infestations with pickleworm and melonworms continue to be observed this week in the Eastern Shore of Virginia. Yesterday, Sep. 2nd 2021, these pests were found feeding on yellow summer squash, green zucchini, and dumpling winter squash crops. All plants sampled in Cape Charles (n= 30) and Machipongo (n= 20) showed at least one fruit and one flower bud with either pickleworms or melonworms, many times with both. If you have any squash crops at the moment, please continue to monitor your plants.

Next week on Sep 8, 2021, Tidewater Agricultural Research and Extension Center (TAREC) will host an “express” peanut field tour. With registration starting at 7:30, attendees will be updated on peanut research on disease, insect and weed management, as well as varieties recently released and in the pipeline for release. Pod maturity of the currently most significant cultivars will be observed. Last but not least, the participants will have the opportunity to be welcomed and interact with the TAREC’ s new Director, Dr. Matthew Chappell. The agenda and map to the tour is here.

This week I have noticed a significant uptick in the amount of peanut leaf spot. It’s mainly in peanuts that have been sprayed once or twice with fungicides and the spray interval is longer than the recommendation on the label. I recommend using Microthiol Disperss (sulfur) tank-mixed with Headline, Lucento, or Provost Silver. I do not recommend stand-alone group 7 fungicides like Miravis and Fontelis. Normally I’d want to repeat the sulfur/fungicide mix in 10 days but this close to digging we may just go with a chorothalonil spray before harvest for leaf spot.

It seems the heat wave we’ve had has arrested Sclerotinia blight to some degree. I just finished rating my plots this morning and the Sclerotinia in the untreated checks hasn’t advanced in about 2 weeks. That’s a good thing. According to the weather forecast this heat will continue until the end of August until it drops significantly to highs in the lower 80’s on September 1. This temperature drop will likely be accompanied with rain. At this point for Sclerotinia blight I’d go with labeled rates of Omega 500 if you spray soon due to the 30 day PHI. Once again, I really want to see a chlorothalonil application as the last fungicide spray of the season for resistance management for leaf spot.

David Langston, VT Tidewater AREC, e-mail: dblangston@vt.edu office phone (757)807-6536; cell (757)870-8498

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).

 

 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.    

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. 

Links to Pest Management Guides   https://resources.ext.vt.edu/

Turf:  

https://resources.ext.vt.edu/contentdetail?contentid=2377&contentname=2021%20Pest%20Management%20Guide%20-%20Home%20Grounds%20and%20Animals

Field Crops:      

https://resources.ext.vt.edu/contentdetail?contentid=2375&contentname=2021%20Pest%20Management%20Guide%20-%20Field%20Crops

Vegetables:  

https://resources.ext.vt.edu/contentdetail?contentid=2379&contentname=2020-2021%20Mid-Atlantic%20Commercial%20Vegetable%20Production%20Recommendations

Sources

http://entnemdept.ufl.edu/creatures/field/fall_armyworm.htm

Luginbill P. 1928. The fall armyworm. USDA Tech. Bull. No. 34.

We at Virginia Tech are starting a pickleworm and melonworm monitoring program. This program involves information exchange between cucurbit growers and extension agents across the state that look for these pests’ damage to blossoms or fruit and report it back to me, Lorena Lopez, a vegetable entomologist at the Eastern Shore AREC. I will send out a weekly alert of the incidence of these pests in the state, based on this information chain and monitoring efforts in cucurbit crops located in Blackburg and the Eastern Shore AREC. The goal is to keep growers updated and help them manage these sporadic late-season pests.

A quick overview of these pests:

Both pickleworms and melonworms feed on wild and cultivated cucurbit species. Pickleworm adults are not active during the day, only at night when females lay their eggs close to flowers or flower buds. The larvae burrow into the fruit where it feeds and develops. Larva color varies from light green to translucent with multiple dark spots and varies in size from 0.05 to 0.6 inches long. Melonworm adults are usually found during the day on the plants but they can be active during day and night. Females lay their eggs on the underside of the leaves. Larva feeds mostly on leaves and can cause damage by skeletonizing them. However, melonworm larvae can also feed on the fruit and on some occasions can borrow into the fruit like pickleworms. Melonworm larvae are usually light green with two white lines in the back and have a similar size to the pickleworm larvae. Adults of both pests are very hard to differentiate.

Early this week we found melonworms in our yellow summer squash at the Eastern Shore AREC. Yellow summer squash is one of the preferred hosts of these pests. All melonworm larvae were found feeding inside the fruit which is uncommon for this pest. We haven’t found any pickleworms yet.

The help and communication network between extension agents, cucurbit growers, and entomologists like myself is vital for the monitoring program. Thus, if you find borrowing damage in the cucurbit flowers or fruit in your respective farm or gardens, please contact me at lorelopezq257@vt.edu

Stay tuned for next week’s update!

Lorena Lopez, Ph.D., Department of Entomology, Eastern Shore AREC, Painter, VA

Corn earworm (=bollworm) moth catches increased this week in our black light traps. The average number of moths caught per night was: Greensville = 7; Hanover = 11; Prince George-Templeton = 6; Prince George-Disputanta = 3; Suffolk = 22. Here is the Table. Thanks to our trap operators Sara Rutherford, Laura Maxey-Nay, Scott Reiter, Josh Holland, and Sally Taylor’s entomology crew.

In our adult vial tests this week (July 29-August 3), 43% of moths survived the 24-hour exposure to cypermethrin (a pyrethroid insecticide) at 5 micrograms per vial (n = 169 moths tested). The season average is 25% survival (446 moths tested).