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
Commercial Ag Updates + Farm Food Safety
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Thrips Active in Vegetable Crops
Veg IPM update 6/12/25
Greetings from the Veg IPM team!
Sweet Corn
Early plantings of sweet corn are silking throughout New Jersey. Moth captures in much of the state (see map) are indicating that 4 day spray intervals are necessary, with pockets of higher pressure requiring 3 day intervals, and a few with lower pressure, indicating 5 or 6 day intervals. 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. We’ve also seen some instances of European corn borer and corn earworm feeding in tassels of scouted corn, but for the most part, their numbers have not been high enough to warrant control efforts prior to silking.
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.
Tomatoes
In southern New Jersey we’re seeing 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. TSWV has already been seen on farms this season. Thrips management can be especially challenging in high tunnels due to a lack of products. Minecto Pro (IRAC 28 + 6) and Exirel (IRAC 28) can be used in tunnels, but only suppress thrips populations (this means they reduce numbers, but do not eradicate them). In the field, Entrust/Radiant (IRAC 5) can be used as well as Torac (IRAC 21A) and Harvanta (IRAC 28). We do not recommend pyrethroids or neonicotinoids for thrips due to resistance in different thrips species. Refer to the previous link for a complete list of best management practices for thrips and TSWV.
We’re also seeing limited aphid 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. However, natural enemies often control aphids, so if counts are low and natural enemies like lacewings, lady beetles, or parasitoid wasps are present, you may avoid sprays. 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. Colorado potato beetles are especially prevalent in eggplants. Please consult the Mid-Atlantic Commercial Vegetable Production guide for appropriate materials for CPB control.
Thrips on a tomato leaf. Photo by Maria Cramer.
Peppers
Peppers have been relatively pest-free so far this season, other than patches of aphids and a few disease issues. As in tomatoes, aphids are often controlled by natural enemies, and using selective insecticides can favor natural enemy activity preventing outbreaks. Before fruit set, the threshold for treatment is 10 aphids per leaf. After fruit set the threshold is 5 aphids per leaf. There are many products registered for aphids in peppers. similar to tomatoes, if only dealing with aphids, we recommend using Beleaf (IRAC 29).
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 continue to see caterpillar activity in heading 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%. For very small caterpillars, 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.
As always, 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.
High Temperatures Predicted this Coming Week – Ways to Prevent Heat Stress
Heat exposure for agricultural laborers should be a consideration when working outside and even in non-airconditioned buildings. When a person’s ability to adapt to heat stress is exceeded, exposure can lead to reduced productivity, mistakes in job performance, increased workplace incidents, and/or heat-related illnesses. Each person’s heat tolerance varies and several factors including type of physical activity, fitness level, underlying health issues, temperature, sun exposure, air movement (wind), and humidity can dramatically impact the potential for heat stress. To determine the level of heat risk, employers should consider the job, the environment, and the worker.
Evaluate the Risk of Heat Stress:
Monitoring the environmental conditions during work times to make management decisions for workers is an important part of preventing heat-related illnesses. Temperature is not the only factor in implementing heat stress management. Humidity is another important consideration. The heat index is a measure of how hot it feels when the relative humidity is factored in with the actual air temperature.
An environmental heat assessment should account for the following factors: air temperature, humidity, radiant heat from sunlight or other artificial heat sources, and air movement. OSHA recommends the use of wet bulb globe temperature (WBGT) monitor to measure workplace environmental heat. OSHA provides this link to calculate the WBGT for a specific location. There is also a NIOSH/OSHA Heat App for Android and iPhone devices that uses the Heat Index as a screening tool.
Management Suggestions for Enhancing Heat Tolerance:
Acclimatization (to heat) is a process of adaptation that involves a stepwise adjustment to heat over a week or sometimes longer. An acceptable schedule for achieving acclimatization is to limit occupational heat exposure to one-third of the workday during the first and second days, one-half of the workday during the third and fourth days, and two-thirds of the workday during the fifth and sixth days. The acclimatization procedure should be repeated if a person misses workdays after days off due to illness, vacation, or other reasons for missing one week or more of job duties.
Fluid replacement:
Provide adequate drinking water for all employees. Recommend to employees they drink plenty of water before work shifts, during work, and after work. Simply relying on feeling thirsty will not ensure adequate hydration. To replace the four to eight quarts of sweat that may be produced in hot environments, people require one-half to one cup of water every 20 minutes of the workday. Potable drinking water kept at a temperature of 59°F or less is recommended.
Physical Fitness: Physical fitness is extremely important. The rate of acclimatization is a function of the individual’s physical fitness. The unfit worker takes 50 percent longer to acclimate than one who is fit.
Increasing Safe Work Practices:
To find management and guidance tools for determining whether to implement heat stress management plans refer to the CDC documents on Heat Stress and Work/Rest Schedules.
The following list of management options should be considered to prevent heat stress for workers:
- Limit exposure time. Schedule as many physical work activities as practical for the coolest part of the day (early morning or late afternoon). Employ additional help or increase mechanical assistance, if possible, to lighten individual workloads.
- Minimize heat exposure by taking advantage of natural or mechanical ventilation (increased air velocities up to 5 mph increase the rate of evaporation and thus the rate of heat loss from the body) and heat shields/shade when applicable.
- Take rest breaks at frequent, regular intervals, preferably in a cool environment sheltered from direct sunlight. Anyone experiencing extreme heat discomfort should rest immediately and be provided with first aid for heat stress.
- Wear clothing that is permeable to air and loose fitting. Generally, less clothing is desirable in hot environments, except when the air temperature is greater than 95°F or a person is standing next to a radiant heat source. In these cases, covering exposed skin can reduce the risk of heat stress.
- A buddy system may also be helpful. It depends on a fellow worker’s ability to spot the early signs of heat stress, such as irritability, confusion, or clumsiness. A ready means of cooling should be available in work areas where heat illness might occur.
Registration Open for 2 Agricultural Supervisor Training Courses: In English and Spanish
Cornell Agricultural Workforce Development will be offering two Ag Supervisory Leadership courses for all agricultural operations starting in June for farms in the Northeastern Region including: Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont. Registration is currently open and closes on June 25. There are separate registration fees for New York residents and out of state residents. See below.
The courses available are:
ASL101-SP: Transición a Supervisor (in Spanish)
Transition to Supervisor helps to develop leaders and focuses on skills to improve communication and manage conflict. Learn how to recognize our inherent biases and how to build better working relationships. Gain insight into your leadership style and learn how to effectively lead diverse and multicultural teams.
Course topics include:
How to make the mental transition to supervisor
How to develop effective working relationships
Essential communication skills
How to be the leader of a multicultural group
How to build better working relationships
Course begins: Friday, June 20, 2025
Live Zoom discussions: Thursdays, June 26 – July 31, 4:00–5:00 PM ET
Register for ASL101-SP Transición a Supervisor
ASL106: Ethics and Employment Regulations (in English)
In ASL106: Ethics and Employment Regulations, you’ll explore how to implement fair and ethical labor practices in agriculture and why they matter. You’ll learn to recognize and prevent sexual harassment, understand wage and hour laws, and apply Equal Employment Opportunity regulations to foster a respectful, inclusive workplace. The course also covers best practices for handling employee discipline and termination.
Course topics include:
Ethics and sustainability
Equal Employment Opportunity, laws and implications
Hiring regulations and practices
Safety issues in agriculture
Farm employee housing
Compensation regulations
Being an ethical supervisor
Course begins: Friday, June 20, 2025
Live Zoom discussions: Thursdays, June 26 – July 31, 3:00–4:00 PM ET
Register for ASL106: Ethics and Employment Regulations
Course costs:
$275 for NYS residents/$325 for out-of-state residents
Scholarship Opportunity for Dairy Producers:
Thanks to the Northeast Dairy Business Innovation Center (NEDBIC), eligible dairy producers can apply for a $100 scholarship to help cover registration fees. Scholarships are available to participants from qualifying states in the Northeast, including Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont.
Questions? Email cu-agworkforce@cornell.edu
Follow us on Facebook: www.facebook.com/cornellagworkforcedevelopment
Survey: Novel Weed Management Strategies for Perennial Crop Systems
Take a Quick Survey Regarding your Needs for Novel Weed Management in Perennial Crops!
Dr. Thierry E. Besançon, Associate Extension Weed Science Specialist, Rutgers University
Our interdisciplinary team of weed scientists and sociologists is conducting research under a Specialty Crop Research Initiative (SCRI) grant to understand perennial crop growers’ priorities regarding novel weed control technologies. This survey aims to identify drivers and barriers to implementing robotic weeding systems in your operations.
We seek to understand your:
- Perspectives on robotic technologies for weed management
- Specific needs and challenges in weed control
- Preferences and limitations when considering new technology adoption
This anonymous, voluntary survey takes approximately 10 minutes to complete. All information collected will be used solely to inform future research questions and outreach activities, and will not be published or distributed. This Friday, May 9th, will be the final day of the survey!
Your participation is invaluable to future developments in the industry regarding new technologies for weed management. We need more inputs from New Jersey perennial crops growers so that they have a say on the direction that weed science research will take in the future!
To contribute, scan the QR code or visit: https://iastate.qualtrics.com/jfe/form/SV_eqzMrFKtlcDjjgO
If you have questions, comments or concerns contact Dr. Thierry Besançon at thierry.besancon@rutgers.edu.
Farm Use of NJ Cottage Food Permit – Webinar 4/30
Learn about the NJ Cottage Food Permit and what value-added products you can, and can’t, make and sell. Meredith Melendez will be hosted by the NJ Farm Bureau Women’s Leadership Committee on April 30th at 6:00 PM. The webinar is free, but registration is required. A tour of the NOFA Farmers Process certified kitchen in Milford will take place on May 7th at 10:00 am, learn more at the webinar!
