With higher temperatures increasing hatch times and spring grains like wheat and rye have drying down, thrips may be more prevalent in vegetable crops, especially when small grains are adjacent to vegetable fields. Thrips are very small and often missed if casually looking at a plant since they hide in blossoms, under sepals, on under sides of leaves and other protected areas on the stems, leaves and flowers. To scout for thrips, look at plant parts mentioned above. It is also important to dissect a flower, pulling back petals and sepals to find hiding thrips. It is difficult to see thrips with the naked eye. Therefore, the use of a hand lens will help.
Most adult thrips are elongate, slender, very small (less than 1/20 inch long), and have long fringes on the margins of both pairs of their long, narrow wings. Immature thrips (called larvae or nymphs) are oblong or slender and elongate and lack wings. Most thrips range in color from translucent white or yellowish to dark brown or black.
Females of most plant-feeding species lay their elongate, cylindrical to kidney-shaped eggs on or into leaves, buds, or other locations where larvae feed. Thrips have several generations (up to about eight) a year. When the weather is warm, the life cycle from egg to adult may be completed in as short a time as 2 weeks.
Thrips will feed on most all vegetable crops – solanaceous crops like eggplant, tomatoes, peppers, white potatoes, cucurbit crops like cucumber, squash and melons, bean crops, allium crops like onions, garlic and leeks and others. This is a photo I took last week of Thrips damage and slender yellow thrips on leaves in a tomato field in Gloucester County.
Thrips feeding on plants can damage fruit, leaves, and shoots and very noticeably affect plants’ appearance. Leaves may be speckled on the top surface from feeding on under sides of leaves by the insect’s sucking mouthparts. High populations often cause significant damage to leaves that may at first glance mimic a foliar disease, but upon closer examination is thrips damage. Damage to fruit, like tomatoes may not appear until fruit ripen and can be seen as gold flecks on red tomato fruit. For many thrips species, by the time their damage is seen, such as after flowers open or fruit forms, the thrips may no longer be present.
Once thrips are identified, control can be difficult when they are found in high numbers. Preventative measures like the use of row covers and reflective mulch have some success. Both conventional and organic insecticides labeled for thrips control can be found in the Rutgers Commercial Vegetable Production Recommendations guide under the sections for individual vegetable crops. Always read the pesticide label for instructions, safety precautions, application rates and restrictions. Since thrips hide in tight areas of plant parts it is important to have good coverage and penetration when applying insecticides to reduce the population of this hard to control pest.
For more detailed information about thrips see the Rutgers Fact Sheet https://njaes.rutgers.edu/pubs/publication.php?pid=FS291
Thrips Active in Vegetable Crops
Vegetable IPM Update 6/5/25
Greetings from the Veg IPM team!
Sweet Corn
With the hot weather, we’re starting to see sweet corn really coming along. Some plantings of sweet corn are silking (especially in the south), so it’s time to think about corn earworm management. Moth captures in the Southern part of the state (see map) are indicating that 4 and even 3 day intervals are necessary in some areas. 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.
Cole Crops
Flea beetle surrounded by feeding damage. Picture by Maria Cramer.
Flea beetle activity seems to be slowing down some, but they are still active in various cole crops. This year, they have been especially prevalent in lacinato kale, 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.
Left: Diamondback moth caterpillar, showing characteristic tapering at each end. Right: Imported cabbageworm caterpillar showing characteristic fuzziness. Pictures by Maria Cramer.
We’re still seeing caterpillar activity 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 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 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.
Tomatoes
In high tunnels and field plantings of 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. We have seen aphid populations decline over the last couple of weeks without spray, probably due to natural enemies predation. 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. We’ve seen very few Colorado potato beetles (CPB) in tomatoes, so while no controls are needed yet, we’ll keep an eye out for increasing populations.
Eggplants
In eggplants we have seen some damaging populations of CPB. For plants under 6 inches, 2 small/1 large larvae per plant is the threshold, while for plants taller than 6 inches, the threshold is 4 small/2 large larvae per plant. Adults are hard to kill, so sprays should target the larvae, with younger/smaller larvae being more vulnerable than older larvae. CPB has resistance to many classes of insecticides and is notorious for quickly developing resistance to new ones, so plan to rotate IRAC groups if you’ve already treated or need to treat more than once. If you haven’t used a neonic (IRAC 4) at planting or in the drip, you can use a foliar neonic like Assail or a spinosyn like Entrust or Radiant (IRAC 5). Avoid IRAC 5 groups if you’ve already used a neonic, because there is risk of cross resistance. Diamide products like Coragen and Exirel (IRAC 28), Rimon (IRAC 15), and Torac (IRAC 21A) should all give good control.
Left: Colorado potato beetle larvae and feeding damage on an eggplant leaf. Right: Adult Colorado potato beetle. Photos by Maria Cramer.
Diseases
We’ve detected bacterial diseases of tomatoes and peppers on a few farms in the central and northern parts of the state (see photos below). Copper may help mitigate symptoms, but some strains have developed resistance due to continued copper use. Other products that may help include Actigard and Quintec. Otherwise, properly managing nutrients and growing conditions for the plant will be crucial for reducing the severity of this disease.
Bacterial leaf spot on tomato. Photo by Amanda Quadrel
Bacterial leaf spot on pepper. Photo by Amanda Quadrel.
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)
Vegetable IPM Update 5/30/25
Greetings from the Veg IPM team! The program welcomes Martina Lavender and Coco Lin as the first two scouts of the season, servicing North and Central Jersey respectively.
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. So far, we haven’t spotted any serious corn pests through visual inspection.
Cole Crops
Flea beetle surrounded by feeding damage. Picture by Maria Cramer.
Flea beetle remain active in various cole crops. This year, they have been especially prevalent in lacinato kale, 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.
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 in the North and diamondback moth in the South) 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 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 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.
Tomatoes
In high tunnels and the first field plantings of 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. We have seen aphid populations decline over the last couple of weeks without spray, probably due to lady beetle predation and parasitism from wasps. 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. We’ve seen very few Colorado potato beetles, so while no controls are needed yet, we’ll keep an eye out for increasing populations.
Colorado potato beetle adult in tomato
Diseases
With little break in the rainy weather, we’re seeing plants stressed by flooding and some bacterial and fungal diseases popping up in tomatoes, peppers, and cole crops. If you’re seeing disease symptoms and need a diagnosis, samples can be sent to Rutgers Plant Diagnostic Laboratory.
We’ve detected bacterial leaf spot of tomatoes and peppers on a few farms in the central and northern parts of the state (see photos below). Copper may help mitigate symptoms, but some strains have developed resistance due to continued copper use. Other products that may help include Actigard and Quintec. Otherwise, properly managing nutrients and growing conditions for the plant will be crucial for reducing the severity of this disease.
Bacterial leaf spot on tomato
Bacterial leaf spot on pepper
Despite the rain, we also saw some rhizoctonia in cole crops, which shows up when transplant plugs dry out. For more information on this disease, check out the recent update in the PPA.
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)
White Pine Weevil Adults Become Active During the Early Weeks of Spring
Many arborists & landscapers often find it difficult to prevent white pine weevil pests (Pissodes strobi), because they are typically applying fertilizer & dormant oil treatments during the control window. In NJ, the control window against feeding white pine weevil adults occurs in March & April. Adults overwinter in the duff beneath trees. The WPW adults will often crawl or sometimes fly to the top terminal leaders of pine, spruce, or Douglas-fir trees. Eastern white pine & Norway spruce species are the most severely attacked & the death of the terminal leaders of these trees will often occur.
Often by July, an infested terminal will brown & die as the weevil larvae have destroyed the vascular tissues. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Treatment timing is critical with this pest, and controlling the adult female before egg laying is necessary. Apply preventative sprays (e.g., pyrethroids) only to the terminal leaders during this time. Before mating & egg laying, adults will feed by chewing holes within the central leader, causing a characteristic pitch flow that becomes white when dry. Then females will lay eggs in new cut-out holes within the top 12 inches of the leader just below the terminal bud.
White pine weevil adults will feed within the upper terminal leaders & cause pitch flow that when dries has a white appearance. This is an early symptom that adults are active & control materials need to be applied. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Black Knot Fungus of Prunus: A Common Landscape Disease
Overview:
Black knot is a cankering fungus disease that infects many trees and shrubs within the genus Prunus. It is caused by the native North American fungal pathogen Apiosporina morbosa. Although black knot fungal galls have been found in a couple of dozen Prunus species, not all species are equally susceptible, and it can be most destructive to certain varieties of cherries and plums (Photo 1).
The following species can be highly susceptible to infections: Japanese plums (Prunus salicina), European and American plums (Prunus domestica & Prunus americana), Sweet cherry (Prunus avium), Mahaleb cherry (Prunus mahaleb), and cultivated species of chokecherries.
This blog reviews the symptoms and signs of Black Knot Disease. It’s management by pruning and fungicide treatments is discussed. Finally, a handful of resistant plum varieties is provided.
Photo 1: This Japanese Plum species is highly susceptible to Black Knot Disease. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Horned Oak Galls & Gouty Oak Galls: Two Exceptions to the Rule
Curiosity of Plant Galls:
Explaining the unusual gall growths or deformities in plants can be challenging. Different galls can be found on virtually any plant part, including leaves, flowers, twigs, bark, or buds of trees and shrubs. Galls caused by insects or mites can typically be identified by the characteristic size, shape, color, and structure that develops.
Insect/mite galls are produced by the interaction of plant hormones with strong plant-regulating chemicals released by the gall maker as they feed. The immature larvae live their entire lives within an individual gall, which provides excellent protection for the larvae as they feed and mature.
This blog contains information on horned and gouty oak galls. When the number of galls infesting an oak is few, tree damage is insignificant. However, tree injuries become more severe when gall numbers reach high levels.
Curious & colorful leaf galls created by maple bladder galls mites may cause alarm to some people but they are mostly harmless. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
An extreme infestation of horned oak galls on branches of pin oak tree. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
