Greetings from the Veg IPM team! Here are this week’s latest pest and disease reports:
Sweet Corn
Pheromone traps for corn earworm (CEW) have been deployed throughout the state. If your corn is approaching silking, it’s time to start thinking about your spray program. Sprays should be initiated at 10% green silks, and continued in intervals as determined by your local CEW pheromone trap counts. Refer to the map below to see this week’s CEW pressure. In South Jersey, the pressure is quite high (3-4 day spray intervals) while North Jersey pressure is lower (5-6 day spray intervals). Remember, when the average maximum temperature for the next 3 days is above 80 degrees, 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.
Caterpillar pests in the whorl and tassel stage. Fall armyworm have not arrived in New Jersey yet, so the main caterpillars that might occur in sweet corn are corn earworm and European corn borer. Historically, European corn borer (ECB) was an important pre-silk pest, but populations have declined drastically in the last 2+ decades since the introduction of Bt corn; in the IPM program, we rarely see more than one or two affected plants in a scouted sweet corn field if we see them at all. We also rarely see ECB occurring in other crops they historically damaged, such as peppers. Because of this, we do not recommend making a routine tassel spray unless you have known pest pressure. It’s important to remember that tasseling corn hosts a wide range of natural enemies (including lady beetles, minute pirate bugs, and syrphid flies) that help suppress secondary pests like corn aphids, as well as pollinators that visit during pollen shed.
If you have historically treated for ECB, we recommend scouting for ECB prior to spraying tassels. ECB feeding damage has a characteristic “shot hole” appearance (photo A below) with distinctly circular feeding holes, whereas CEW damage can appear in more elongated/ragged patches. If you follow the feeding damage down into the whorl, you may spot frass (caterpillar waste), and often the larva. ECB are small, smooth, tan-colored caterpillars with a black head (A and B). CEW larvae grow larger than ECB, come in a variety of different colors, and have speckles and hairs. Unlike ECB, they will have a light, tan-colored head capsule.
European corn borer surrounded by characteristic “shot hole” feeding damage (A) and an ECB feeding in a tassel (B). Photos by Amanda Quadrel.
Corn earworm caterpillars in corn tassels. Note light-colored head capsules, colorful bodies with dots and hairs. Pictures by Maria Cramer.
If you are scouting your own sweet corn for larva, choose ten random locations in the field and check five consecutive plants at each location. If 12% or more of the plants show signs of fresh caterpillar feeding, an early spray may be warranted. We haven’t seen caterpillar feeding above threshold levels at any of our scouted sites, so there’s been no need for sprays before the onset of silking. If you do find that larval pressure in your sweet corn is above threshold and your corn is nearing/in the tasseling stage, we recommend starting with a diamide like Coragen (IRAC Group 28). These products tend have lower toxicity to bees compared with other IRAC groups, which helps protect bees that may be visiting during pollen shed.
Cole Crops
Left: Diamondback moth caterpillar, showing characteristic tapering at each end. Right: Imported cabbageworm caterpillar showing characteristic fuzziness. Pictures by Maria Cramer.
Flea beetles seem to be slowing down a bit, but caterpillars are still active (diamondback moth and imported cabbageworm specifically). Treatment thresholds vary between crops and growth stage, but for heading cole crops between early vegetative and cupping, the treatment threshold is 30% infested plants. Once the heads form, the threshold for caterpillars becomes 5%. Sprayable Bt products (IRAC 11A, 0d PHI) such as Dipel, Xentari, or Javelin, or insect growth regulator products like Rimon (IRAC 15, 7d PHI) and Intrepid 2F (IRAC 18, 1d PHI) can be effective on young caterpillars and will also be gentler on natural enemies that control other cole crop pests. Proclaim (IRAC 6, 7/14d PHI) will also work for caterpillars, but be mindful of the longer PHI. For crops that are nearly ready for harvest, materials approved for caterpillar control with shorter PHIs include:
Entrust/Radiant (IRAC 5, 1d PHI)
Torac (IRAC 21A, 1d PHI)
Exirel (IRAC 28, 1d PHI)
Incipio (IRAC 30, 1d PHI).
These additional products may work better for diamondback moth or larger larvae. For Bt products and contact insecticides, coverage on the undersides the leaves is essential. Some products have different restrictions or PHIs for different types of brassica crops, so make sure to read the label thoroughly before applying, especially if your cole crop plantings are a mix of heading and leafy cole crops.
Tomatoes and Peppers
Drying down grains and skyrocketing temperatures are leading to serious increases in thrips. In south Jersey, higher thrips numbers are coming with outbreaks of tomato spotted wilt virus (TSWV). While there is no easy or perfect solution to thrips and TSWV, there are a number of actions that can help, even at this stage. First, scout plantings for plants with viral symptoms and remove them (see figure below for example of a plant with virus symptoms). This is important for preventing secondary spread in the field from infected to healthy plants. Often multiple plants will be affected and symptoms will appear over a couple of days or weeks, so keep checking the planting for plants that need to be rogued. If you need help identifying TSWV, please contact us with the form at the end of this post.
Tomato spotted wilt virus symptoms on a greenhouse tomato. Picture by Maria Cramer.
Second, scout plants for thrips. This is important even if you have already sprayed for thrips, because you need to know how well the spray worked. Unfortunately, there is no established treatment threshold for thrips, especially when TSWV is a risk. In the veg IPM program we scout for thrips by checking two full leaves per plant on 50 plants per field (see example of thrips on a tomato leaf below). These 50 plants are divided into 10 5-plant sub-samples evenly spaced in the field. We consider a total of 5 thrips in a subsample to be a high count, but have seen TSWV transmission even at lower levels. Many people sample flowers, but this is complicated because flowers host non-pest thrips species that can’t be identified from pest species by the naked eye. Additionally, research suggests that even the best thrips treatments will not reduce thrips counts in the flowers, so this may not be very informative for determining how effective a treatment was. Based on this, we advise monitoring foliage to get a sense of thrips pressure in a planting.
Thrips on a tomato leaf. Picture by Maria Cramer.
Managing thrips with insecticides is challenging because many populations of thrips have developed resistance to one of the best products for thrips (Radiant, IRAC 5). Because of this, we do not recommend using Radiant in south Jersey for thrips. The remaining products vary in efficacy and most are limited to two applications, which is key for avoiding insecticide resistance. In order to plan which products to use, consult our earlier article on thrips management which lists the IRAC group number, efficacy, and application limits for products. Note that pyrethroids (IRAC 3) are often labeled for thrips, but we do not recommend these due to resistance and their potential to flare up spider mites.
Pay attention to fertility: over-fertilized plants are more attractive to thrips.
Finally, separating late plantings as far as possible from early plantings that have thrips and/or TSWV can help slow movement of populations into those late plantings and keep them healthier.
We have seen elevated spider mite counts in some tunnel tomatoes as well. Otherwise, tomatoes and peppers have been relatively free of aphids, stinkbugs, and caterpillars.
Cucurbits
We now have our sentinel plots for Cucurbit Downy Mildew (CDM) planted at the Snyder Farm in Pittstown and RAREC in Bridgeton. These plots contains two varieties of cucumber (a susceptible and resistant variety), watermelons, cantaloupe, and various types of winter squash. As soon as we detect CDM, either in our sentinel plots or elsewhere in the state, we will send out an alert immediately.
As a reminder, the new 2026/2027 Mid-Atlantic Commercial Vegetable Production Guide is now available for free online (click here) or as spiral-bound hard copies that can be purchased at your local county extension office. Consult this guide for a more comprehensive list of materials that are labeled for specific crops and pests.
We want to give a huge thanks to our scouting team for keeping an eye on things for us throughout the season!
North NJ: Connor Colonese, Shayne Miller, and Cassandra Dougherty
South NJ: Alex White, Renee Carter, and Peter Combs
Authors: Amanda Quadrel (Northern NJ Veg IPM coordinator) and Maria Cramer (Southern NJ Veg IPM coordinator)
Questions or comments? Contact us below:
