Rutgers University | New Jersey Agricultural Experiment Station | Pesticide User Responsibility

May 8, 2025 and

Vegetable IPM Update 5/08/24

Sweet Corn

We’ve put out corn earworm pheromone traps throughout the state. While silking corn is the main target of CEW activity, we set the traps early to detect overwintering moths, which have become more common with warmer winters. As a reminder, we’re no longer using blacklight traps as of this year, and we’ll be reporting pheromone trap counts in the Plant Pest Advisory as the season progresses.

Cole Crops 

A shiny black beetle with straight antennae stands on a leaf surrounded by circular feeding holes.

Flea beetle surrounded by feeding damage. Picture by Maria Cramer.

Flea beetle are active in various cole crops. This year, they have been especially prevalent in Napa cabbage and bok choy. Young plants are especially vulnerable to attack from flea beetles. The treatment threshold for flea beetles in heading cole crops is 50% infestation.

 

Two picture, the picture on the left shows a smooth caterpillar that tapers at both ends. The picture on the right shows a caterpillar that is fuzzy all over and does not taper at either end.

Left: Diamondback moth caterpillar, showing characteristic tapering at each end. Right: Imported cabbageworm caterpillar showing characteristic fuzziness. Pictures by Maria Cramer.

We’re seeing caterpillar activity (imported cabbageworm and diamondback moth) in cabbage and other cole crops. Treatment thresholds vary between crops and growth stage, but for heading cole crops between early vegetative and cupping, the treatment threshold is 30%. At this stage, sprayable Bt products (IRAC 11A) such as Dipel, Xentari, or Javelin can be effective on young caterpillars. Other 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.

 

Tomatoes

In high tunnel tomatoes, we’re seeing limited aphid, thrips, and spider mite activity. If dealing with primarily aphids, products such as Beleaf (IRAC 29) are recommended, especially if plants have reached the flowering stage. For thrips, Entrust, Radiant (IRAC 5) and Torac (IRAC 21A) can be used. For spider mites, Nealta (IRAC 25) is an effective material that is more friendly to beneficial insects, but Portal (IRAC 21A) and other materials can be used to manage populations.

 

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

Authors: Amanda Quadrel (Northern NJ Veg IPM coordinator) and Maria Cramer (Southern NJ Veg IPM coordinator)

 

Filed Under: Organic Production, vegetable, Vegetable Crops Tagged With: , , , ,
June 21, 2024

The Curious Case of the Virus Infected Tomato Fruit

Original Article published on 6 June 2024 by Dr. Jerry Brust, University of Maryland Extension

Ben Beale, educator from St. Mary’s County found an odd thing last week. He found in a grower’s high tunnel, tomato fruit that had the symptoms of a virus infection, but there were no foliar symptoms on any of the plants. Some fruit on a cluster had symptoms while other fruit on the same cluster looked perfectly fine. Ben had the fruit tested and got a fast response from Jill Pollok at the University of Delaware Diagnostic Clinic and it was Tomato Spotted Wilt Virus. The cultivar in question Big Beef Plus has TSWV resistance. There could be one or two possibilities for TSWV symptoms showing up in a resistant cultivar and for fruit symptoms but not any foliar symptoms of the virus.

We will look at how tomatoes can get infected by the TSWV (if you already know how this works skip down to the next paragraph). Tomato spotted wilt virus (TSWV) is an obligate parasite, i.e., it must have a living host and must be moved from one plant to another by thrips or through cuttings or possibly seed. This disease can affect tomato and other Solanaceae crops as well as lettuce, beans and cucumber. TSWV may occur in the field but tends to affect greenhouse and high tunnel crops more severely. The virus is transmitted most efficiently by Western flower thrips (WFT) (Frankliniella occidentalis), and less so by Onion thrips (Thrips tabaci), Tobacco thrips (Frankliniella fusca) and several other thrips species.  It is not transmitted by Eastern flower thrips (Frankliniella tritici). Only immature thrips can acquire the virus, which they can acquire within 15 minutes of feeding, but adults are just about the only stage able to transmit the virus. Adults can transmit the virus for weeks. It may take 2 – 4 weeks from when the adult thrips first feeds on a plant until initial symptoms are observed. Because of this TSWV appears to worsen in plantings over time.

Why are we seeing fruit symptoms but little if any foliar symptoms? The most likely explanation is that TSW viruliferous thrips fed on the flowers or very young fruit. The resistance to the TSWV is expressed (active if you will) in the non-reproductive parts of the plant but not expressed to any extent in the reproductive parts (flowers and fruit) of the plant. Even though the flower and fruit can act as an entry point into the plant the resistant tomato does a good job of limiting the virus into any other areas of the plant. Thus, under low to moderate feeding pressure (1-4 thrips/flower) only the fed upon fruit or possibly a few other fruits on the same cluster become infected. The other possibility is that the TSWV resistance in Big Beef Plus is intermediate and under environmental stress it may not be ‘complete enough’ to protect all of the plant.

The first question above as to why is the virus showing up at all in a resistant cultivar can be explained by the above paragraph. But there may be another possibility although not in this particular case, that we will have to watch out for in the coming years. And that is resistance- breaking virus variants. The Sw-5b gene (Sw-5) is the most widely used resistance gene for TSWV in tomato. It not only provides resistance to TSWV but also resistance to a several associated viruses including Tomato chlorotic spot virus (TCSV) and Impatiens necrotic spot virus (INSV). The presence of the Sw-5 gene in tomato plants confers resistance to TSWV by a hypersensitive defense response that causes local lesions on the leaf, preventing the spread of the virus from the infection site through the plant. In 2022, symptoms of TSWV were observed in North Carolina tomato fields on cultivars that had the gene for TSWV resistance (Sw-5). The cultivars from different farms had symptomatic foliage and fruit. Samples were collected from both farms and subjected to sequencing to identify and confirm the presence of resistance-breaking variants, which they did. I mention this because NC is very close by, many growers get their tomato transplants from NC and because the resistance-breaking occurred in the last year or so. These resistance-breaking variants may start to show up in our fields and I am guessing that when they do, we will see 20-40% viral foliar infection and possibly worse in the fruit of resistant plants. For now, we should keep using the resistant cultivars, but watch closely for any breakdown of the resistance.

Resources: 2023. First Report of Resistance-Breaking Variants of Tomato Spotted Wilt Virus (TSWV) Infecting Tomatoes with the Sw-5 Resistance Gene in North Carolina. K. Lahre, R. Shekasteband, I. Meadows, A. E. Whitfield, and D. Rotenberg. Plant Disease vol. 107.

This article appears in Volume 15, Issue 4 of the Vegetable and Fruit News.

Filed Under: Vegetable Crops Tagged With: , ,
June 13, 2024

Identifying and controlling leaf mold in high tunnel & greenhouse tomato production

Leaf mold occasionally appears in high tunnel or greenhouse tomato production in New Jersey. However, under ideal conditions the disease will develop in field-grown crops. The fungus will cause infection under prolonged periods leaf wetness and when relative humidity remains above 85%. If relative humidity is below 85% the disease will not occur. Therefore, the proper venting of high tunnels and greenhouses on a regular basis is important. The pathogen can survive (overwinter) as a saprophyte on crop debris or as sclerotia in the soil. Conidia (spores) of the fungus can also survive up to one year in the soil.

Symptoms of leaf mold on infected tomato plant. Note the bright yellow leaves and the olive-green spores developing on the undersides of leaves.

Symptoms of leaf mold on infected tomato plant. Note bright yellow leaves and olive-green spores developing on undersides of leaves.

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Filed Under: Vegetable Crops Tagged With: , , , ,
June 10, 2024

Diagnosing Southern blight and White mold in tomato and pepper

There have been a few reports of Southern blight (Sclerotinia rolfsii) and White mold (Sclerotinia sclerotiorum) on tomato and pepper in New Jersey. Southern blight is much more common in vegetable areas south of the state where summer temperatures remain hotter (above 90°F) for longer periods of time. Like white mold, it can survive in the soil for many years. Symptoms of Southern blight include infection at the base of the stem at the soil line. The resulting infection will girdle the plant causing wilt and death. The fungus will produce white, cottony mycelium and very small, spherical sclerotia which are often have a tannish, brown color.

White mold is more common than Southern blight in New Jersey, and like Southern blight, once introduced into a field or high tunnel it can very difficult to control. The pathogen produces large black sclerotia on the surface and inside infected stems. If sclerotia of either pathogen make their way back into the soil, both can survive for years causing significant problems.

All infected plants need to be removed immediately and disposed of properly to help reduce the chances of sclerotia returning to the soil.

For more information on chemical control please see the 2024/2025 mid-Atlantic Commercial Vegetable Production Recommendations Guide.

Infected root

Symptoms of Southern blight on infected pepper plant. Note the numerous, small white to tan colored sclerotia on the stem.

Infected stem

White mold of tomato. Note the large black sclerotia developing inside the brittle stems.

Filed Under: Vegetable Crops Tagged With: , , ,
June 9, 2024

Diagnosing pith necrosis in tomato

Symptoms usually begin to appear on random plants throughout the field as green fruit begins to mature. The bacterium (Pseudomonas corrugata) is ubiquitous to soils and develops when weather conditions (cooler nights/very hot, humid days) and cultural practices (i.e., excess heavy N use) lead to favorable conditions for disease development. Symptoms include the development of irregular greasy (at first), brown lesions on main stems and branches. Late pruning (i.e., suckering) can provide entry points for the bacterial disease. Internally, stems will become chocolate brown and mushy. High humidity is necessary for disease development. High nitrogen and lower night temperatures are associated with Pith Necrosis development, where it has been reported around the state this past week. Control begins with cultural practices such as avoiding working in fields with wet foliage, avoiding late pruning, tying when plants are wet, and watching the amount of N applied to plantings. Infected plants can be rouged from field and most often it does not spread to nearby uninfected plants.

Filed Under: Vegetable Crops Tagged With: , ,
May 19, 2024

Identifying and controlling Botrytis in high tunnel and greenhouse tomato production

Botrytis, or gray mold, caused by the fungus, Botrytis cinerea, can cause significant losses in high tunnel and greenhouse tomato production if not controlled properly. The pathogen can rapidly spread during periods when structures are closed and when relative humidity remains high for long periods of time. This often occurs when outside weather remains cool and damp while heating is needed. Gray mold is favored by temperatures from 64° to 75°F and requires only high humidity (not leaf wetness) to become established. The pathogen has a large host range and once established in an enclosed structure it can be very difficult to control (UMASS). The fungus can survive/overwinter as mycelia or sclerotia in plant debris and in organic soil matter (NCSU).

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