April 7, 2026 and

Allium Leafminer Update 4/7/2026

Greetings from the Veg IPM team!

We detected the first Allium Leafminer oviposition scars on garlic in Burlington County, NJ today (see photos below). Adults are likely active throughout the state at this time. Be on the lookout for oviposition scars on both crop alliums and wild alliums such as wild onion/garlic and ramps. You can also use yellow sticky cards to monitor for adult presence in the field.

Allium Leafminer oviposition scars. Notice the neat line of white dots near the tips of the leaves. Photos by Maria Cramer.

Allium Leafminer (Phytomyza gymnostoma) is a small grey-bodied fly with a yellow head (A). In warm, still weather, you may see adult flies settling on foliage. The females lay eggs in neat rows, leaving behind a line of white dots on the leaves (B). As the larvae hatch and begin to feed, they will tunnel downwards, causing damage to leaves and bulbs. ALM have two generations per year; the first in early spring, and the second occurring in the fall. Crops such as chives, scallions, garlic, onions and leeks are attacked by ALM, but leeks and scallions seem to be the most affected. 

An allium leafminer adult (A) and oviposition scars (B). Photos by Maria Cramer a7l;/nd Amanda Quadrel

If you are concerned about crop injury due to ALM, floating row covers, kept on until the first flight ends (around the end of May) can restrict ALM’s access to vulnerable plants. Reflective mulches may also provide some additional crop protection. Adults and larvae can be targeted through well-timed insecticide sprays. Materials labeled for ALM control include spinosyns (IRAC 5- Radiant or Entrust (OMRI approved)), pyrethroids (IRAC 3A- Mustang Maxx, Proaxis, and Warrior II), neonicotinoids (IRAC 4A- Scorpion, Venom), the insect growth regulator Trigard (IRAC 17), and diamide products (IRAC 28- Exirel, Minecto Pro). The newly registered product Vertento (IRAC 30) may also be used for ALM control. However, growers who have trouble managing onion thrips may want to save group 28 and 30 products for thrips sprays, as both groups have season use limits. The first spray application of a material should be completed 2- 3 weeks after initial detection of ALM (either oviposition scars or the fly itself). Subsequent sprays should be completed in 1–2-week intervals. Two or three sprays should provide adequate control. As always, be sure to follow label rates and application instructions for any pesticide that you plan to use.

For more pictures and detailed information on the biology and management of ALM, Cornell has an excellent fact sheet that can be found here: https://cals.cornell.edu/integrated-pest-management/outreach-education/fact-sheets/allium-leafminer. In the meantime, feel free to reach out to us if you have any questions.

~Amanda Quadrel and Maria Cramer, Senior Program Coordinators- Vegetable IPM

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Filed Under: Organic Production, vegetable, Vegetable Crops
March 19, 2026 and

Allium Leafminer Update 3/20/2026

Greetings from the Veg IPM team, and happy first day of Spring! As we are slowly transitioning into warmer weather, now is a great time to be thinking about Allium Leafminer (ALM), a pest of many bulbous crops such as onions, scallions, chives, and garlic.

Allium Leafminer (Phytomyza gymnostoma) is a small grey-bodied fly with a yellow head (A). In warm, still weather, you may see adult flies settling on foliage. The females lay eggs in neat rows, leaving behind a line of white dots on the leaves (B). As the larvae hatch and begin to feed, they will tunnel downwards, causing damage to leaves and bulbs. ALM have two generations per year; the first in early spring, and the second occurring in the fall. Crops such as chives, scallions, garlic, onions and leeks are attacked by ALM, but leeks, and scallions seem to be the most affected. 

An Allium leafminer adult (A) and the characteristic oviposition scars left behind after females lay eggs (B)

An Allium Leafminer adult (A) and the characteristic oviposition scars left behind after females lay eggs (B). Photos by Maria Cramer and Amanda Quadrel

 

Be on the lookout for oviposition scars on both crop alliums and wild alliums such as wild onion/garlic and ramps. You can also use yellow sticky cards to monitor for adult presence in the field. However, another way to the predict the first generation’s activity is by using growing degree days (GDDs). The first emergence of ALM adults occurs around 250 GDDs (Base temperature: 39˚F). Below is a table that shows the number of GDDs that have accumulated from January 1st to March 19th (the date this post was written), as well as the number of GDDs predicted to accumulate by March 24th.

Location  GDDS for 3/19 GDDs for 3/24 (forecast)
Northern NJ (Chester) 102 129
Central NJ (Cream Ridge) 162 202
Southern NJ (Upper Deerfield) 187 231

 

While ALM risk is currently low for northern and central NJ, areas in southern NJ could reach 250 GDDs by the end of next week, thus being at a higher risk for ALM activity. To find out how many GDDs have accumulated in your specific area, the NEWA website: https://newa.cornell.edu/ has a helpful GDD calculator. From the NEWA home screen, select your nearest weather station from the drop down menu or map at the center of the page. Next, scroll down to the “Weather Tools” section on the lower right side of the page, and select “DD Calculator”. Select your start date (1/01/26) and end date (typically the day you check), as well as Degree Day Type (Base 39 F) from the menu at the left of the page.  The site will automatically generate a table of the number of accumulated GDDs for the specified date range and a forecast of predicted GDD accumulations over the next five days.

If you are concerned about crop injury due to ALM, you may want to prepare for control efforts. Floating row covers, kept on until the first flight ends (around the end of May) can restrict ALM’s access to vulnerable plants. Reflective mulches may also provide some additional crop protection. Adults and larvae can be targeted through well-timed insecticide sprays. Materials labeled for ALM control include spinosyns (IRAC 5- Radiant or Entrust (OMRI approved)), pyrethroids (IRAC 3A- Mustang Maxx, Proaxis, and Warrior II), neonicotinoids (IRAC 4A- Scorpion, Venom), the insect growth regulator Trigard (IRAC 17), and diamide products (IRAC 28- Exirel, Minecto Pro). The newly registered product Vertento (IRAC 30) may also be used for ALM control. However, growers who have trouble managing onion thrips may want to save this active ingredient for thrips sprays, as there is a limit of two applications per season. The first spray application of a material should be completed 2- 3 weeks after initial detection of ALM (either oviposition scars or the fly itself). Subsequent sprays should be completed in 1–2-week intervals. Two or three sprays should provide adequate control. As always, be sure to follow label rates and application instructions for any pesticide that you plan to use.

For more pictures and detailed information on the biology and management of ALM, Cornell has an excellent fact sheet that can be found here: https://cals.cornell.edu/integrated-pest-management/outreach-education/fact-sheets/allium-leafminer. In the meantime, we will keep our eyes open for any ALM activity in our respective areas and provide updates in the next coming weeks. We are looking forward to warmer weather and a productive season! 

~Amanda Quadrel and Maria Cramer, Senior Program Coordinators- Vegetable IPM

Questions or concerns? Get in touch with us by filling out the form below:

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Filed Under: Organic Production, vegetable, Vegetable Crops
February 25, 2026 and

Have a plan for managing thrips and TSWV in tomatoes and peppers in 2026

Thrips and tomato spotted wilt virus (TSWV) management were major challenges for multiple South Jersey growers in 2025, as well as in the previous few years. Several growers reported losing entire tomato plantings to the virus. Peppers were less impacted than tomatoes, but TSWV outbreaks did occasionally occur. As we move into pepper and tomato transplant production and the growing season for greenhouse tomatoes, having a multi-pronged approach for managing thrips and TSWV will give you the best chance of protecting your crop and avoiding losses. Below are key practices that can help keep thrips populations as low as possible:

Start clean. When transplants are infested with thrips prior to planting out, field infestations tend to occur early and be very difficult to control. To start clean:

  • Never produce transplants in the same greenhouse with ornamentals. Ornamentals can harbor thrips and many are asymptomatic hosts for TSWV.
  • Monitor thrips in planthouse with sticky cards and scouting (Fig. 1). There are no established thresholds for thrips in the greenhouse, but many growers use the first appearance of thrips as an action threshold.
  • Keep greenhouses and high tunnels weed-free. Weeds can host both thrips and TSWV.
  • If buying in transplants, segregate and monitor incoming transplants to ensure that they are not bringing in thrips.
  • Treat transplants with imidacloprid (e.g. Admire) or Cyantriniliprole (Verimark) before setting in the field

A yellow rectangular sticky card held to a stake with a clothespin has caught several small insects.

Fig. 1. A sticky card being used to monitor greenhouse pests. Photo by S. Rettke.

 Manage plantings to prevent the spread of thrips and TSWV from alternative hosts into tomato plantings. Thrips are attracted to pollen-producing plants, so populations can build up on plants that flower early, such as strawberries and small grains, then move into tomato plantings. Additionally, thrips can also overwinter on weeds. Using these facts, reduce the movement of thrips into tomato plantings by:

  • Controlling weeds throughout the farm, especially in and around high tunnels
  • Separating field plantings from greenhouses/tunnels, strawberry fields, and small grains
  • Separating successive field plantings as much as possible. This way, if thrips and/or TSWV get out of control in one planting, they will not move directly into the next planting.
  • Scouting for tomato spotted wilt virus symptoms (Fig. 2). Immediately rogue symptomatic plants to avoid secondary spread within the field.

Fig. 2. TSWV symptoms in tomato: a) curling and yellowing foliage symptoms, b) distortion and brown shoulder symptoms on green fruit, and c) bulls-eye symptoms on ripe fruit. Photos by M. Cramer.

Use metallized plastic and resistant varieties.

  • Use metallized plastic mulch when possible (Fig. 3). Metallized mulches reflect sunlight, disrupting thrips navigation and making it harder for them to colonize plants. These plastics are widely used in states like Florida that have historically had serious thrips problems. Because these mulches reflect solar radiation, they lower bed temperatures, and will slow down tomato growth early in the season. This should be taken into account when planning to use them.
  • Use TSWV resistant tomato and pepper varieties. While some farms have reported resistance-breaking TSWV, others continue to report that resistance is still holding up.

Fig. 3. Metallized plastic laid in the fall to control onion thrips in alliums. Photo by A. Quadrel.

Use best practices around insecticides. Thrips are difficult to manage with insecticides because they tend to hide in hard to reach parts of the plant or in the soil as well as their rapid ability to develop resistance. For example, many thrips populations in south Jersey are resistant to Radiant (IRAC 5), making this insecticide ineffective for management. Pyrethroid (IRAC 3) resistance is also widespread. Many of the insecticides labeled for thrips are only partly effective, and none are able to “knock down” high populations. To get the best efficacy out of insecticides:

  • Know what your populations are: Monitor thrips populations and treat when populations start building, but are still low.
    • Scout 5- 10 locations in field at least once a week
    • At each location in the field, pick a group of 5 consecutive plants and check 2 leaves on each plant (10 leaves total per location)
    • Count the number of thrips on the leaves (Fig. 4). Research from North Carolina shows that the species of thrips vectoring TSWV (western flower thrips) are most reliably found on the leaves rather than the flowers
    • Threshold: Action should be taken if counts are increasing towards ~ 5 thrips per 10 leaves on average
  • Rotate modes of action as much as possible. We believe that thrips populations tend to be highly localized, and thus you are managing insecticide resistance for your population of thrips specifically. The more you manage resistance, the more product options you will continue to have.
  • Monitor thrips populations after treatment to assess efficacy (some systemic products, such as Beleaf and Verimark may take several days to ~a week to impact thrips populations)

Note: The vegetable IPM program offers scouting services throughout New Jersey if you are unable to scout your plantings (you can find a description of services here). We also offer training for scouts employed by growers. Finally, private companies can also provide scouting services.

Fig. 4. Five thrips on a tomato leaf.

Plan what products you will use and when. The following table lists conventional products that can be used for tomato pest management. Choose products from a variety of IRAC groups to prevent resistance development and prolong efficacy.

IRAC group Product name Ai Efficacy

* = suppression only

 Notes on use
1A Lannate Methomyl Good New EPA restrictions on annual applications (<13 lbs AI/acre/year) and mitigations for runoff and drift. Not labeled specifically for thrips in tomatoes, but can be used
1B Dimethoate Dimethoate Good Not labeled specifically for thrips in tomatoes, but can be used
4A Admire Imidacloprid Good Only labeled for tobacco thrips. For treating transplants before transplanting
5 Radiant/

Entrust

 Spinetoram/

Spinosad

 Excellent, except where resistant No more than 3 applications in a season. Widespread resistance issues in South Jersey
13 Pylon Chlorfenapyr Excellent Only for greenhouse tomato production– i.e., not for transplants or field production. Not to be used on tomatoes that are <1” diameter at harvest.
15 Rimon

 

 Novaluron Good* Foliar. No more than 2 applications against thrips in a year. Can be used in greenhouses and high tunnels. Larvae only
21A Torac Tolfenpyrad Fair Foliar. No more than 2 applications in a season
23 Movento Spirotetramat ? Foliar. No more than 2 applications in a season (at 5 fl oz/A thrips rate). Larvae only
28 Harvanta Cyclaniliprole Fair* Limit of 3 applications per season (at 16.4 fl oz/A thrips rate)
28 Verimark Cyantraniliprole Fair* Tray drench just prior to planting or drip irrigation. No more than 2 applications per year. Limits when ai is being used foliarly (e.g. Exirel) as well
28 Exirel Cyantraniliprole Fair* Foliar. Recommend early in the season for new transplants. Limitations on ai use
29 Beleaf Flonicamid Excellent Only labeled for thrips when used through drip. No more than 2 applications per year
30 Incipio Isocycloseram Excellent New for 2026. No more than 2 applications per year

When using pesticides, the label is the law. Always make sure the product you use is registered in your state and for your crop(s). Follow all application restrictions.

Biological insecticides. There are many biological products that are labeled for tomatoes in the greenhouse, tunnel, and field. While we do not have efficacy information for these, some growers have reported good results in tunnels and greenhouses with Grandevo WDG (Chromobacterium subtsugae and spent fermentation media), LALGUARD M52 OD (active Metarhizium brunneum), and Bronte (inactivated Burkholderia rinojensis cells and spent fermentation media). Biological insecticides may have specific storage and handling instructions in order to achieve maximum efficacy.

In conclusion, use a multi-strategy approach for thrips and TSWV management. In particular, use resistant varieties and preventative practices to reduce thrips populations and TSWV spread on your farm. When using insecticides, time applications based on action thresholds, monitor efficacy, and rotate IRAC groups in order to prevent the development of insecticide resistance.

By: Maria Cramer, Amanda Quadrel, and Andy Wyenandt.

 

Filed Under: Organic Production, vegetable, Vegetable Crops Tagged With: , , ,
January 16, 2026

It’s never too early to be thinking about corn earworm — Free webinar on CEW management

The corn earworm traps from the Vegetable IPM program may be stored away for the winter, but the vegetable IPM team is always thinking about CEW management. We want to bring sweet corn producers’ attention to a free webinar put on by a regional team of corn earworm experts that will cover two important topics: Bt traits and silk sprays. Information below:

Management Options for Corn Earworm in Sweet Corn

Virtual Webinar Thursday, February 19, 2:00-3:30PM

Registration link:https://umd.zoom.us/meeting/register/ZxoBY8rkTbyWNTuQHhq7zw#/registration

Description

Our regional team (more information at CEWIPM.org) has been working to improve management of corn earworm in sweet corn. This webinar will include two talks the first focused on using Bt hybrids and the second on using insecticides during silking for management.

Presentations

Bt Sweet Corn Hybrids: Efficacy, Pest Pressure, and Regional Monitoring Results

Veronica Yurchak and Galen Dively

Efficacy, Timing, and Safety Considerations for Silk Spray Insecticides

Kelly Hamby, Jared Dyer, Dan Gilrein, David Owens, John Mahas, Brian Nault, Brian Currin, Tom Kuhar, and Kemper Sutton

Stacks of conical wire mesh traps on a concrete floor

Hartstack traps are used to monitor CEW populations and determine spray intervals during the growing season. This winter, our traps are stored at the Cumberland County Extension office where they will receive some TLC to get them ready for the coming season. Photo by Maria Cramer. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Interested in implementing IPM in your sweet corn? Rutger’s vegetable IPM program offers scouting and corn earworm trapping throughout New Jersey. Contact Maria Cramer (south) or Amanda Quadrel (north/central) to get involved.

By: Maria Cramer and Amanda Quadrel

Filed Under: training, vegetable, Vegetable Crops
January 15, 2026 , and

Monitoring for RB-Tomato Spotted Wilt Virus in transplant production

Tomato spotted wilt virus (TSWV) has caused significant problems for some fresh-market tomato and pepper growers in New Jersey the past few growing seasons. Although not uncommon, economic losses these past few years have been extensive.

TSWV is vectored by various species of thrips, a common vegetable insect pest that seems to be on the incline and very difficult to control in vegetable production throughout the state. The most important vector of TSWV is the western flower thrips, Frankliniella occidentalis. It’s mode of transmission is persistent propagative, meaning that thrips nymphs have to feed on a TSWV-infected plant, whereby followed by a short incubation period (lasting from hours to days), the virus is then persistently transmitted throughout the rest of the insect’s life span.

Importantly, TSWV cannot be passed from infected females to eggs; and TSWV is not transmitted in seed.

The western flower thrips and TSWV both have a wide host range! Western flower thrips host range includes: tomato, pepper, onion, celery, cucumber, lettuce, potato, basil, strawberry; a wide range of herbaceous ornamentals (e.g., impatiens, geranium, marigold, petunia, dahlia, gerbera daisy, carnation) as well as many common weeds (e.g., pigweed, chickweed, lambs quarter, thistle, galinsoga). TSMV can infect over 1,000 plant species from more than 90 plant families.

In 2022, samples of a TSWV-infected fresh market tomato variety with Sw-5b resistance were collected in southern New Jersey and sent for analysis. Results determined that RB (C118Y) TSWV was present in the state; and the strain found in New Jersey was similar to the RB TSWV found in fresh-market tomato from Mexico and processing tomato in California suggesting a high potential for its widespread movement. Since 2022, isolated cases of RB-TSWV have been found in New Jersey each growing season.

So, where do we go from here? Based on the isolated reports of TSWV being found on resistant fresh-market tomato in New Jersey the past few growing season, it does not appear that RB TSWV is currently widespread throughout the state. However, this may likely change.

All vegetable growers, those who produce their own transplants or bring them in, need to carefully evaluate their thrips monitoring and mitigation programs this winter and spring.

  1. Start fresh. Prior to the transplant production season, clean and disinfect the greenhouse or any other structure where you might be holding transplants. Remove any weeds within and around the structure. Use sticky cards to monitor the potential carryover thrips population during the winter months, especially if you have any plant material in the greenhouse during those months.
  2. Never produce or keep tomato or pepper transplants you start yourself or bring in, in the same greenhouse with any ornamental plants.
  3. Segregate any transplants that are brought into your operation from your own transplants, as well as segregate different source of transplants as best you can.
  4. Evaluate all incoming transplants for thrips damage.
  5. Treat all incoming transplants with an insecticide immediately.
  6. Use yellow sticky cards to continually monitor for thrips populations in the greenhouse from the start of the transplant season until the end.
  7. Consider using biological or natural control(s) in the greenhouse.
  8. The use of silver reflective mulches have been shown to reduce thrips populations in fields.
  9. Develop a season-long insecticide program prior to the production season; from applying an insecticide at transplanting through cover sprays until harvest.
  10. Monitor thrips populations and feeding damage in the field with regular scouting and sticky cards.
  11. Closely monitor thrips feeding injury on pepper and tomato fruit during the production season.
  12. Proper weed control is essential since many weeds may harbor the virus or infected thrips. This includes areas around the production field.
  13. Rogue out any suspicious looking plant(s) prior to transplanting, or any suspicious looking plant early in the production season (e.g., any plant that starts to stunt out early) to help mitigate the within field spread.

Growers should continue to utilize TSWV-resistant tomato and pepper varieties realizing the effectiveness of those in limiting TSWV is becoming compromised. All growers need to continue to follow best management practices (such as those listed above) and pay careful attention to current weaknesses in their production practices and thrips control programs and adjust their management practices heading into 2026 growing season.

If you suspect RB-TSWV in transplant production or the field later this year please contact your county agent.

by: Andy Wyenandt, Maria Cramer, and Amanda Quadrel

References:

Macedo MA, Melgarejo T, Cespedes M, Rojas M, Lazicki P, Turini T, et al. (2024) An all-out assault on a dominant resistance gene: Local emergence, establishment, and spread of strains of tomato spotted wilt orthotospovirus (TSWV) that overcome Sw-5b-mediated resistance in fresh market and processing tomatoes in California. PLoS ONE 19(7): e0305402.

Tomato spotted wilt virus on pepper and tomato. Inga Meadows and Andy Cooper, NCSU 2024

Gautam et al., 2022. First report of a resistance-breaking strain of tomato spotted wilt orthotospovirus infecting Capsicum annuum with Tsw resistance gene in Texas. Plant Dis. 107:1958.

 

Filed Under: Organic Production, vegetable, Vegetable Crops Tagged With: ,
October 11, 2025 and

Veg IPM Update 10/10/25

Greetings from the Veg IPM team! This will be the last regular update of the season. Should an urgent issue arise, we will put out a special edition of the Plant Pest Advisory.

Sweet Corn

For those who still have silking corn, Corn earworm pressure is finally letting up throughout the state (see map). Rotation is important for avoiding resistance, and there are four IRAC groups that are registered in silking sweet corn: 1 (carbamates), 3 (pyrethroids), 5 (spinosyns), and 28 (diamides). CEW is at least partly resistant to several pyrethroids, so a spray program should not rely solely on pyrethroids, although they can be useful in tank-mixes or as pre-mixed products, such as Besiege or Elevest (Group 28 + Group 3). For detailed information about resistance and potential spray programs, the University of Delaware has an excellent resource on corn earworm management.

Spray intervals based on nightly pheromone moth captures for the southern part of New Jersey. Note that not all locations in the IPM program are currently trapping. This map is based on the following thresholds: 0 moths = 6-7 day schedule, 1 moth = 5 day spray schedule, 2-20 moths = 4 day spray schedule, 20+ moths = 3 day spray schedule.

Allium Leafminer Alert

Allium leafminer adults and oviposition scars have been detected across various plantings throughout the state, indicating that the second generation of the pest is active. ALM can cause injury to chives, scallions, garlic, onions and leeks, but leeks and scallions seem to be the most affected. Look for neat rows of white spots descending from the upper tips of allium leaves (see photos below). If ALM is a threat to your alliums, we recommend treating now, with subsequent sprays being made in 1-2 week intervals. Approved materials for controls include spinosyns (Radiant, Entrust (OMRI approved)), pyrethroids (Mustang Maxx, Warrior), neonicotinoids (Scorpion, Venom), and the insect growth regulator Trigard. Two or three sprays should provide adequate control.

The picture on the left shows a small fly with a yellow head leaving a row of oviposition scars in a scallion leaf as it lays eggs. The picture on the right shows alliums planted on black plastic, with some of the leaves showing rows of pale, triangle-shaped oviposition scars.

An allium leafminer adult (A) and oviposition scars (B). Photos by Maria Cramer (A) and Amanda Quadrel (B).

Tomatoes

Thrips and caterpillar pests have significantly decreased in most tomato plantings. We are still seeing a lot of spider mites, although spraying for them this late in the season is unlikely to be worthwhile. When sampling spider mites, check 10 upper leaflets in at least 5 sites per field. Typically, the treatment threshold is 2 mites per leaflet on average (one of the individual leaves that makes up the compound tomato leaf).

Tomato leaves that are covered in yellow colored stippling and webbing being held up for the camera.

Severe spider mite infestation showing extensive stippling and webbing. Photo by Maria Cramer.

Cole Crops 

We are seeing many different kinds of caterpillars in fall cole crop plantings, including diamondback moth, imported cabbage worm, cabbage looper, cross-striped cabbageworm, and yellow striped armyworm. All cole crop seedlings can tolerate up to 10% infestation for these caterpillar. For heading cole crops between early vegetative and cupping, the treatment threshold is 30%. As heads form, the treatment threshold goes down to just 5% infestation. Sprayable Bt products (IRAC 11A) such as Dipel, Xentari, or Javelin can be effective on young imported cabbage worm, cross-striped cabbageworm, and yellow-striped armyworm caterpillars. Diamondback moth has resistance to many insecticide groups, and pyrethroids (IRAC 3A) and Bt products (IRAC 11A) are not effective for their management. Besides Bt, materials approved for caterpillar control include Entrust/Radiant (IRAC 5), Proclaim (IRAC 6), Torac (IRAC 21A), and Exirel (IRAC 28).  For Bt products and contact insecticides, coverage on the undersides the leaves is essential.

Caterpillar pests of cole crops. A) Diamondback moth — smooth and tapered at each end. B) Imported cabbageworm — fuzzy and not tapered. C) Cabbage looper — characteristic looping behavior. D) Cross-striped cabbage worm — distinctive stripes, usually occurs in groups. Photos A-C by Maria Cramer, photo D from iNaturalist COO.

Besides downy mildew in cole crops, the main diseases that are common are alternaria leaf spot, which is a fungal disease, and black rot, which is a bacterial disease. Alternaria leaf spot develops in cool wet weather and is favored by overhead irrigation. Fungicide programs that incorporate multiple modes of action (see the Mid-Atlantic Veg Guide) are needed to prevent leaf spot development. Black rot and other bacterial diseases of cole crops are hard to manage chemically. The best way to prevent their development is through selection of resistant varieties, hot water seed treatment, and rotation (2+ years between planting a brassica crop). Copper treatments provide some control.

Top picture shows a brassica leaf with two large bulls-eye brown spots on either side of the mid rib. Bottom picture shows two cabbage plants where outer leaves have triangle shaped brown lesions radiating out to the leaf edge.

A) Alternaria: characteristic water-soaked bulls eye lesions. B) Black rot: triangle-shaped lesions on the leaf edges. Pictures by Renee Carter.

Lettuce
We have been scouting lettuce on an as-requested basis, and have seen some severe thrips feeding in lettuce. This feeding starts as piercing-sucking damage on the lower leaves and progresses until leaves completely dry out and die. While the damage is worst in the bottom leaves, we have seen thrips throughout the head of lettuce. In situations where thrips on the farm are Radiant-resistant (this will be evident from thrips management on earlier crops like tomatoes), Exirel (IRAC 28) can provide some control. Simply removing the dried up bottom leaves at harvest may be an option, depending on your market.

Top picture shows close up on a single leaf which is covered with stippling damage. Bottom picture shows whole plant with browned drying up bottom leaves.

Thrips damage in lettuce, progressing from stippling damage to drying up and dying leaves. Pictures by Maria Cramer.

Pumpkins and Other Cucurbits

Pumpkin harvests are underway, and few issues have been seen in fields. Downy mildew of pumpkins and squash still has not been detected in the area and is unlikely to be a threat for this year. Powdery mildew is still active; continue treating if your fruit will be in the field for the next several weeks. Leaves will serve as protection against sunscalding of the fruits.

As always, please consult the Mid-Atlantic Commercial Vegetable Production Guide for a comprehensive list of materials that are labeled for specific crops and pests. As always, be sure to follow label rates and application instructions.

The Vegetable IPM Program wishes to thank the following Field Technicians, without whom much of the information presented weekly here would not be available.

Southern team: Renee Carter and Kris Szymanski

Northern team: Martina Lavender, Coco Lin, and Cassandra Dougherty

Filed Under: Organic Production, vegetable, Vegetable Crops