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.
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.
Today, Aug 26 2021, we pod blasted a few peanut cultivars
grown at the Tidewater AREC in large plots to observe pod maturity at this
time. While the peanuts planted in the first week of May might be ready in
20-25 days from now, those planted in late May are approximately 30 days from the
optimum maturity. Keep in mind that weather is also a decisive factor;
therefore, sampling for maturity again in 10-14 days from now will allow to
pinpoint more accurately the day when peanuts are ready for digging.
Wynne planted on May 25.Walton planted on May 3.Sullivan planted on May 25. Bailey II planted on May 5.Bailey planted on May 25.
In an effort to better recognize Virginia’s soybean producers, Virginia Soybean Association is completely revamping the 2021 Soybean Yield Contest! Through a combination of checkoff dollars and sponsorship support, we’re happy to announce the a new and improved soybean yield contest.
There will be two categories: full-season and double-crop. There is no restrictions on irrigation (irrigated fields are accepted). Most of all the awards for the top 3 winners in each category has increased substantially due to our sponsors (see below).
1st Place – $2,500
2nd Place – $1,000
3rd Place – $500
This has already garnered a lot of interest. We look forward to receiving your entries.
Both melonworms and pickleworms have been detected in squash plantings yesterday in Cape Charles and Machipongo farms. Approximately, 80% of the plants showed at least one flower bud/fruit with borrowing injuries. Most of the squash fruit and flower buds contained 1-2 melonworms in the latest stages of their larval development (4th-5th instar, Fig. 1). Pickleworms on the other hand, have just started to show up in the area and only 1st to 3rd larval instars were found, most of them on top of flower buds and growing fruit (Fig. 2). Both pests were also detected in one cucumber planting on approximately 30% of the plants sampled. These pests have been detected in squash plantings in Blacksburg this week at a lower infestation rate compared to the Eastern Shore.
Well-timed insecticide applications are crucial for the management of these pests and recently hatched caterpillars that haven’t borrowed into the plant tissue are more susceptible to insecticides. However, once they borrow inside fruits and flower buds, contact insecticides are usually not enough to suppress these pests. The use of systemic insecticides is preferred.
Useful tip: Pickleworms and melonworms are NOT the same as squash vine borers. Squash vine borers borrow into the stems causing severe damage and eventually plant death (Fig. 3), unlike pickleworms and melonworms that feed mostly on the reproductive parts of the plant and occasionally the leaves.
Fig. 1. Melonworm larvae inside squash fruit.
Fig. 2. Pickleworm larva on top of flower bud.
Fig. 3. Squash vine borer inside the stem.
If you find borrowing damage in cucurbit crops on your respective farm or gardens, please contact me at lorelopezq257@vt.edu
Stay tuned for the next update!
Lorena Lopez, Ph.D., Department of Entomology, Eastern Shore AREC, Painter, VA Photos by Lorena Lopez.
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.
Pickleworm larva (J. L. Capinera, UF/IFAS)
Melonworm larva (L. Buss, UF/IFAS)
Fruit damage caused by pickleworm and melonworm larvae (L. Lopez, Virginia Tech)
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).
Recent rains and cooler temperatures have maxed out out the risk for leaf spot and Sclerotinia blight of peanuts. In fungicide trials at the Tidewater AREC in Suffolk, VA I counted 9 hits of Sclerotinia blight in 70 row-ft in one untreated plot. Late leaf spot was evident at low levels in the lower canopy as well. Hopefully 2 preventive sprays have been made for leaf spot, but many growers may not have made an application for Sclerotinia blight at this time.
I know my above comments sound like doom and gloom, but growers typically have less disease pressure than we do at our experiment station as they use longer crop rotations. Most of our plots are on a 2-3 year rotation where most growers in Virginia rotate land to peanuts every 4 or more years. Crop rotation remains our best tool to reduce risk of disease losses in peanuts in the Commonwealth.
Peanut leaf spot can occur in all peanut fields, but soilborne diseases such as stem rot and Sclerotinia blight are problems in less than half of production fields, which is a good thing. Most growers know which fields they have problems with these diseases which allows them to treat them differently than most fields. With Sclerotinia blight risk high and already observed, growers need to make preventive fungicide applications of fungicides specific to this disease. if an application of Miravis/Elatus has been made in the last 10-14 days you should be good for another 10-14 days depending on weather conditions. If you haven’t applied a fungicide that effectively controls Sclerotinia blight, I recommend Omega 500 at 1 – 1.5 pts tank-mixed with a leaf spot fungicide in fields with histories of the disease. I also advise growers to scout these fields to determine if disease is present and to assess the effectiveness of fungicides already applied. The best place to look for Sclerotinia blight is in the largest, deepest vines in the field and in low areas that tend to hold moisture longer. The disease may cause leaves to wilt on individual stems (flagging) and tan, necrotic tissue that has white, fully fungal growth can be observed on these stems near the stem base beneath the canopy. See picture of typical Sclerotinia blight on peanut stems in the image below.
Tan lesions and white fungal growth on peanut vines affected by Sclerotinia blight. At the top of the picture just left of center you can see the small, black sclerotia on one of the stems.
You may see flagging from Tomato Spotted Wilt Virus (TSWV) but no lesions on stems or fungal growth is present. I have had to take a closer look at several plants that had flagging leaves only to find that it was TSWV causing symptoms.
Typically a follow-up spray for Sclerotinia blight is warranted 21 days after the initial application of Omega 500. If you are using the 2-spray program of Miravis/Elatus there is no need to make an application of Omega 500 unless you are more than 30 days prior to harvest and disease pressure and weather conditions pose a high risk of severe damage.
If you have questions related to peanut disease management please feel free to contact me.
David Langston – e-mail dblangston@vt.edu, cell (757) 870-8498, office (757)807-3536
Right now most peanut growers are deciding when to apply the first leaf spot fungicide and which fungicide to use. The recommendation the past few years has been to start spraying peanut fungicides at R3 (beginning pod) but no later than July 10th. I recommend using a chlorothalonil product (Bravo, Echo, Equus and others) at the 1.5 pt/A rate. I also recommend using Alto at 5.5 fl oz/A + 1.0 pint/A of chlorothalonil as an alternative. Tebuconazole (Folicur) is often tank-mixed with chlorothalonil at 7.2 fl oz/A but I wouldn’t expect a lot of leaf spot activity with tebuconazole as resistance to that fungicide by the leaf spot pathogens is widespread. Tebuconazole may still provide some activity against southern stem rot (A.K.A. “white mold”). Subsequent fungicide applications for leaf spot can be made according to the last effective spray date (LESD) using the Virginia Leaf Spot Advisory on the Peanut-Cotton Infonet https://webipm.ento.vt.edu/cgi-bin/infonet1.cgi or using a 14-day calendar-based approach.
In some fields growers may see early spotting that could be from herbicide injury or irregular or “funky” leaf spot. Irregular leaf spot can look an awful lot like early leaf spot but generally occurs earlier in peanut development regardless whether environmental conditions are favorable or not for early leaf spot. According to the Virginia Leaf Spot Advisory the risk of developing leaf spot has been low to moderate across all location thus far, but with current rain conditions that may change. No known cause has been attributed for irregular leaf spot and it has not been shown to cause economic losses. My main concern is that irregular leaf spot may cause growers to react to what they think is the beginning of an early leaf spot epidemic and spray needlessly or use more expensive products to control leaf spot. With irregular leaf spot, brown spots may be surrounded by yellow halos or large yellowed areas, defoliation may or may not occur, and spores are never present on spots. Anytime you suspect irregular or actual fungal leaf spot you can bring or have samples sent to the Plant Diagnostic Clinic at the Tidewater AREC for identification. If you have question or concerns please don’t hesitate to contact me.
David Langston, Plant Pathologist, Virginia Tech Tidewater AREC 6321 Holland Rd., Suffolk, VA 23437 cell phone (757) 870-8498 office phone (757) 807-6536 e-mail dblangston@vt.edu
The entomology program at the Tidewater AREC has spent this week scouting cotton fields across Virginia growing regions. First, I want to thank our technicians, graduate students, ANR Agents, Johnny Parker, and especially, our cooperating farmers. Cotton surveys are made possible through funding by Cotton Inc. and the Virginia Cotton Board.
I want to emphasize that overall plant bug numbers are very low, square retention very high, and the majority of fields will not be blooming by next week. Fields above threshold at this time are rare and sporadic. Use restraint when making pesticide applications without scouting first because we have many weeks left to manage insect pests. The most important time to manage plant bugs is during the first two weeks of bloom (see below graph from Seth Dorman’s work) and late-planted cotton is at higher risk of yield loss. Spraying at threshold (pre-bloom = 8/100 sweeps and <80% square retention) is as good as spraying every week (which is a pretty bad idea for secondary pest infestations, logistics, and costs).
Until the 2nd week of bloom, scout fields using a sweep net. Pay attention to areas of the field where cotton is rank and or borders other crops, but do not make decisions based on hot-spots alone.
Several insecticides are effective for plant bugs in cotton pre-bloom including neonicotinoids (imidacloprid, thiamethoxam), acephate with or without novaluron (Diamond), flonicamid (Carbine), and sulfoxaflor (Transform). Rotating insecticides, opposed to spraying a broad-spectrum like acephate season-long, will save you trips across the field. See the below table from our 2020 experiments demonstrating that using sulfoxaflor (Transform) alone, flonicamid (Carbine) alone, rotating a neonicotinoid (Centric) with sulfoxaflor (Transform), and using acephate with novaluron (Diamond) resulted in fewer trips across the field when compared to acephate alone. Also note that acephate with novaluron (Diamond) resulted in a second spray only at the end of August when it is debatable whether we have time to make a harvestable boll (i.e., it is likely that yield protection was based on a single spray). ALL INSECTICIDE APPLICATIONS YIELDED THE SAME. I do not recommend pyrethroids because of documented resistance in Virginia. They may or may not work on your farm. Pyrethroid resistance increases as the season progresses. Please make the decision that is right for your farm based on your experience and knowledge.
Please let me know if you have questions and or concerns. Email, call, or text. I hope everyone has a safe and happy 4th!
