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).

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.

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

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!