Vegetable Crops Edition

Seasonal updates and alerts on insects, diseases, and weeds impacting vegetable crops. New Jersey Commercial Vegetable Production Recommendations updates between annual publication issues are included.
 
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July 31, 2025

Quick reviews of fungicide chemistries, FRAC groups, and fungicide resistance management

Did you know that first EBDC fungicide was registered for use in vegetable crops in 1964 followed by chlorothalonil in 1966. Historically speaking, the first New Jersey Vegetable Production Recommendations Guide was produced in 1969 and was only 33 pages long (it’s 502 pages now). Things have changed significantly over the past 55 years when it comes to pest management! For a quick review on fungicides, FRAC groups, and managing fungicide resistance development please click on the links below.

Using tank mixes and fungicide rotations and information on FRAC group 4, FRAC group 7, and FRAC group 3 and FRAC group 11 fungicides.

As a reminder, the new 2024-2025 Mid-Atlantic Commercial Vegetable Production Recommendations Guide can be purchased at most county offices and is also available for FREE on-line here!

Filed Under: Vegetable Crops Tagged With:
July 30, 2025

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.

[Read more…]

Filed Under: Vegetable Crops Tagged With: , , , ,
July 29, 2025

What’s up with corn smut!

There have been numerous reports of corn smut throughout the state of New Jersey the past few weeks.

Corn smut (also called common smut), caused by Ustilago maydis, is found infecting corn throughout most of the world. In most years, corn smut is reported in New Jersey , but reports are limited to just a few plantings and just a few ears of corn. Corn smut gets its name from the sooty, black masses of teliospores that found on infected plants. Symptoms are tumor-like galls that vary in size from less than 1 cm to more than 30 cm in diameter. All meristematic tissues are susceptible to infection; and galls can develop on ears, tassels, stalks, shoots, and mid-ribs of infected plants (Pataky and Snetselaar, 2006). From the time of infection, it takes about 10 days for early symptoms to show up; followed up with a maturation of black spore masses within swollen galls about three weeks after infection (Figure 1).

Figure 1. Corn smut.

The fungus can overwinter as teliospores in crop debris or the soil and remain viable for many years. It is thought that the teliospores (i.e. the black spores – it is estimated that up to 200 billion spores are produced in a medium-size gall!) are unimportant in the summer they are produced, but more importantly act to overwinter and cause infections the next growing season (Pataky and Snetselaar, 2006) .

There is no general agreement on weather conditions that are most favorable for common smut, although most reports indicate that common smut is prevalent following rainy, humid weather (Pataky and Snetselaar, 2006).  Galls on leaves and stalks of seedlings often are observed following strong thunderstorms with heavy winds, especially when plants are injured by blowing soil (Pataky and Snetselaar, 2006).  Factors that reduce the production of pollen or inhibit pollination also increase the occurrence of ear galls of common smut. Thus, hot, dry, drought-like conditions often cause asynchronous pollen production and silk emergence which results in poor pollination and common smut may be prevalent if U. maydis is readily disseminated to stigmas of unfertilized ovaries during or immediately following these hot, dry conditions (Pataky and Snetselaar, 2006). Thus, some associate the occurrence of ear galls with droughts although the droughts probably affect the prevalence of ear galls primarily by increasing the number of unpollinated ovaries with rapidly growing silks (Pataky and Snetselaar, 2006).

Although there has been a great amount of research in controlling corn smut with fungicides (c0nventional and biological), adjusting fertility, crop rotation, sanitation, and seed treatments, the best management practice for limiting losses due to corn smut are planting smut resistant corn varieties (Pataky and Snetselaar, 2006). Although, none are completely resistant to the pathogen.

Unfortunately, for much of New Jersey this summer the weather conditions (the extended drought-like conditions in July) followed by the heavy isolated rains leading most likely to poor pollination periods and timing of corn smut infections led to the situation we are seeing now. Growers with significant smut issues might consider removing and destroying smutted ears to reduce inoculum loads, plan on choosing sweet corn varieties with resistance next year, and changing irrigation practices to help reduce crop stress during pollination periods.

References:

Pataky, J. and Snetselaar, K. 2006.​​​​​​ Common smut of corn (Syn. boil smut, blister smut). Plant Disease Profiles, The Plant Health Instructor. Volume 6. <doi.org/10.1094/PHI-I-2006-0927-01>

For more detailed information on corn smut, it’s biology, and history please see the link to the following article referenced above by Jerald Pataky and Karen Snetselaar at The Plant Health Instructor Website hosted by APS.

https://www.apsnet.org/edcenter/disandpath/fungalbasidio/pdlessons/Pages/CornSmut.aspx

 

Filed Under: Vegetable Crops Tagged With:
July 26, 2025

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.

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July 26, 2025

Diagnosing Important Diseases In Tomato – Reference Guide

The following images consist of important diseases in tomato. These images can be used as a quick reference for diagnosing important fungal and bacterial pathogens. For best results, please turn your device (i.e., cell phone) sideways. For information on commercial control recommendations, please visit the tomato section of the 2022/2023 Mid-Atlantic Commercial Vegetable Production Guide. Additional information for home gardeners is located at the bottom of the Table.

Early blight Septoria leaf spot Anthracnose fruit rot
Early blight on tomato
Early blight lesion on fruit Ground rot infected green fruit Ground rot sporulating on fruit
Bacterial leaf spot Bacterial canker Bacterial speck
White mold Southern blight Late blight on foliage
White mold sclerotia in infected stem Southern blight sclerotia on infected stem Late blight infected fruit
Collar Rot caused by Alternaria spp.

For the homeowner or non-commercial grower there are a number of Rutgers/NJAES Fact Sheets available on-line:

Rutgers University/NJAES Fact Sheet (FS547) ‘Diagnosing and controlling important fungal pathogens of tomato in the home garden‘.

Rutgers University/NJAES Fact Sheet (FS548) ‘Diagnosing and controlling Phytophthora blight in the home garden’.

Rutgers University/NJAES Fact Sheet (FS1124) ‘Vegetable disease control recommendations for the home garden’.

For other Rutgers University/NJAES Fact Sheets for tomato please click here.

Filed Under: Vegetable Crops Tagged With:
July 25, 2025 and

Veg IPM Update 7/25/25

Greetings from the Veg IPM team!

Sweet Corn

Corn earworm moth captures are increasing, leading to 3- or 4-day spray intervals being needed throughout the state. When temperatures are high (>85 degrees F), shorten the spray interval by one day. 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). Corn earworm 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.

 

Fall armyworm (FAW) infestations are beginning to pick up in some locations. Young larvae will cause damage known as “window paning”, in which the top surface of the leaf is eaten away, leaving behind thin, white, membranous-looking scratch marks. As the larvae age, these feeding marks become more ragged (A). The damage can look somewhat similar to European corn borer feeding, but FAW damage will be more severe and will lead down into the whorl. The caterpillars will have a dark head capsule with a distinct, inverted Y-shaped suture (B). We recommend using products other than diamides (IRAC Group 28) when treating whorl-stage infestations, as diamides are important to save for silk protection. Effective products include Lannate (Group 1A), Radiant (Group 5), Intrepid (Group 18), Intrepid Edge (5+18), and Avaunt (Group 22). Note that Avaunt can only be used through tassel push.

Fall armyworm damage (A) and larva (B). Note the distinct suture on the head, which will differentiate FAW from other caterpillar pests of corn. Photos by Amanda Quadrel

 

We are seeing a significant amount smut it sweet corn. Normally, smut infects the ears, however we have seen smut growths on vegetative stages (leaves and tassels) as well. Smut was prevalent in our area in 2024, and you can read more about it in an update written last year. Smut is rarely economic and there are no effective treatments for it. Being able to correctly identify it can help rule out other plant problems.

Corn smut in A) whorl-stage leaves, and B) pre-tassel tassels. Pictures by Renee Carter (A) and Nick Vergara (B)

 

Tomatoes

Throughout New Jersey we’re continuing to see high thrips counts both in tunnels and in the field, although numbers have been higher in tunnels. We consider more than 5 thrips on 10 leaves a high count. Other guides suggest 3-5 thrips per flower or the presence of stippling damage on fruit to be a treatment threshold. Thrips management is especially important because of their ability to vector tomato spotted wilt virus (TSWV), a growing concern in New Jersey where we have resistance-breaking strains. We have seen several locations in our scouting program with small outbreaks of TSWV (in both peppers and tomatoes) so far. Scouting and roguing out these plants while continuing to manage thrips should help prevent serious losses. Additionally, follow best management practices for reducing TSWV risk throughout the season.

Top picture shows curled tomato leaf with brown circles covering it. The bottom picture shows a pepper plant with distorted, slightly cupped leaves, and yellow markings, including circles, on many leaves.

A) TSWV on a tomato leaf. Note the circle-shaped brown lesions. B) TSWV on a pepper plant. Note the distortion of leaves all over the plant as well as the yellow wavy lines and circles visible on leaves. Photos by Maria Cramer.

Caterpillar pests have begun showing up in throughout the state. We’ve seen some fruit damage, and tomato fruitworm (AKA corn earworm), beet armyworm, and hornworms on plants and fruit. There are no reliable thresholds for determining when to spray for these caterpillar pests, however scouting and consulting the corn earworm pressure map for the state will help give a sense of risk to the crop. When corn earworm pressure indicates a 3 or 4 day spray interval in corn (2-20 moths per night) as is currently the case in much of the state, tomatoes should be scouted weekly for feeding damage. Pyrethroid resistance is widespread in tomato fruitworm/corn earworm and beet armyworm, so other classes of insecticides should be used if management is needed.

With consistent hot temperatures, we’re seeing more spider mites in tomato plantings. Spider mites tend to be worse in hot, dry conditions, and especially thrive in tunnels. Their populations often dramatically increase following broad-spectrum insecticides, which reduce their natural enemies. The first sign of their presence is often light-colored stippling seen on the top surface of tomato leaves. The mites causing this damage are usually found on the undersides of leaves. For spider mites, Nealta (IRAC 25) and Oberon (IRAC 23) are effective materials that are more friendly to beneficial insects, but Portal (IRAC 21A) and other materials can also be used to manage populations.

Tomato leaves with tiny yellow or white dots on visible on the top surface of the leaf.

Spider mite stippling visible when looking at tomato leaves from above. The spider mites are found on the undersides of the leaves. Photo by Maria Cramer.

 

Peppers

In terms of most insect pests, peppers have been looking very good. We have seen aphids, spider mites, and thrips at low levels so far, however it’s important to keep in mind that thrips can transmit TSWV to peppers as well, and so monitoring and staying on top of thrips populations is crucial. As with tomatoes, finding and roguing out infected plants is important as well. See previous section for an example of TSWV symptoms in peppers.

Anthracnose on ripe pepper fruit. Note concentric circles and sporulation. Picture by Maria Cramer.

With drying weather, peppers have been fairly disease-free, but we have seen instances of anthracnose. Anthracnose is an important disease to scout for and be able to identify as removing infected fruit and strip-picking surrounding fruit is key to managing its spread. Your fungicide program can also help manage anthracnose — for more information, read more here.

As a reminder, in June we saw several pepper weevils on pepper weevil traps in Cumberland and Salem Counties. Read more about pepper weevil biology and management here. If you think you may have pepper weevil on your farm or are interested in monitoring, please contact Maria Cramer.

Cole Crops 

We are no longer seeing many flea beetles in cole crops, but we continue to see caterpillar activity. Treatment thresholds vary between crops and growth stage, but 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 caterpillars. Other materials approved for caterpillar control include Entrust/Radiant (IRAC 5), Proclaim (IRAC 6), Torac (IRAC 21A), and Exirel (IRAC 28). Diamondback moth (the primary caterpillar found in southern NJ) has resistance to many insecticide groups, and pyrethroids (IRAC 3A) are not effective for their management. For Bt products and contact insecticides, coverage on the undersides the leaves is essential.

Two caterpillars on brassica leaves. Diamondback moth caterpillar on the left is smooth and tapered at each end. Imported cabbageworm on the right is fuzzy.

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

 

Pumpkins and Other Cucurbits

Cucurbit downy mildew was first reported on 7/11/25 on cucumbers in central NJ and has been found on cucumbers and cantaloupe at the Snyder Research Farm in Pittstown. Growers should be applying protectants on cucumbers and cantaloupes for cucurbit downy mildew at this time. As of this post, we haven’t found any instances of the disease on pumpkins, squash, or watermelon. For information on how to build an effective cucurbit down mildew control program, please reference this post by Dr. Andy Wyenandt and consult the Mid-Atlantic Production Guide for additional materials that can be used.

Cucurbit downy mildew symptoms on the upper surface (A) and underside (B) of cucumber leaves and symptoms on cantaloupe (C). Photos by Amanda Quadrel

In pumpkins, we’ve seen few insect issues, although adult squash bugs and egg masses are starting to appear. Consider treating for squash bug if you see more than one egg mass or group of nymphs per plant (see photos below).

Squash bug eggs (A), newly hatched nymphs (B), and an adult (C). Photos by Amanda Quadrel

 

Powdery mildew is also beginning to pick up. If more than one leaf in a 50 leaf sample is infected, fungicide programs for powdery mildew should be initiated.

Powdery mildew on pumpkin leaf. Photo by Amanda Quadrel.

We have also seen isolated cases of anthracnose, bacterial wilt, plectosporium, and phythophthora root rot. A preventative diseases management plan based on recommendations from the Mid-Atlantic Production Guide is important for suppressing many of these diseases. If you suspect diseases in your pumpkins (or other cucurbits), reference the “Diagnosing important diseases in Cucurbit crops” guide or send/bring samples to Rutger’s Plant Diagnostic Lab.

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, Kris Szymanski, and Nick Vergara

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

Filed Under: Commercial Ag Updates, Organic Production, Uncategorized, vegetable, Vegetable Crops