Thrips and tomato spotted wilt virus (TSWV) management were major challenges for multiple South Jersey growers in 2025, as well as in the previous few years. Several growers reported losing entire tomato plantings to the virus. Peppers were less impacted than tomatoes, but TSWV outbreaks did occasionally occur. As we move into pepper and tomato transplant production and the growing season for greenhouse tomatoes, taking a multi-pronged approach to managing thrips and TSWV gives you the best chance of protecting your crop and avoiding losses. The following practices can help keep thrips populations as low as possible.
Start clean. When transplants are infested with thrips before planting, field infestations tend to occur early and are very difficult to control. Never produce transplants in the same greenhouse with ornamentals. Ornamentals can harbor thrips, and many are asymptomatic hosts for TSWV. Monitor thrips in the planthouse with sticky cards and regular scouting. There are no established greenhouse thresholds, but many growers use the first appearance of thrips as an action threshold. Keep greenhouses and high tunnels weed-free, since weeds can host both thrips and TSWV. If you buy transplants, segregate and monitor incoming plants to make sure they are not bringing in thrips. Treat transplants with imidacloprid, such as Admire, or cyantraniliprole, such as Verimark, before setting them in the field.
© S. RettkeFig. 1. A sticky card being used to monitor greenhouse pests
Manage plantings to prevent the spread of thrips and TSWV from alternative hosts into tomato fields. Thrips are attracted to pollen-producing plants, so populations can build up on early
© M. Cramer flowering crops like strawberries and small grains before moving into tomatoes. Thrips can also overwinter on weeds. Reduce movement into tomato plantings by controlling weeds throughout the farm, especially in and around high tunnels. Separate field plantings from greenhouses, tunnels, strawberry fields, and small grains whenever possible. Separate successive field plantings as much as you can so that if thrips or TSWV get out of control in one block, they do not move directly into the next. Scout regularly for TSWV symptoms and immediately rogue symptomatic plants to prevent secondary spread within the field. Use metallized plastic mulch and resistant varieties when possible.
Right: Fig. 2. TSWV symptoms in tomato: a) curling and yellowing foliage symptoms, b) distortion and brown shoulder symptoms on green fruit, and c) bulls-eye symptoms on ripe fruit
Metallized plastic mulch can help reduce thrips colonization. These mulches reflect sunlight, which disrupts thrips navigation and makes it harder for them to settle on plants. They are widely used in states like Florida where thrips pressure has historically been high. Because metallized mulches reflect solar radiation, they lower bed temperatures and can slow tomato growth early in the season. This should be considered during planning.
Use TSWV-resistant tomato and pepper varieties. While some farms have reported resistance-breaking strains of the virus, others continue to find that resistance is holding up and provides valuable protection.
© A. Quadrel
Fig. 3. Metallized plastic laid in the fall to control onion thrips in alliums
Follow best practices when using insecticides. Thrips are difficult to manage with insecticides because they hide in hard-to-reach parts of the plant and in the soil, and they develop resistance quickly. In South Jersey, many populations are resistant to Radiant in IRAC Group 5, making it ineffective in some fields. Pyrethroid resistance in IRAC Group 3 is also widespread. Many labeled products are only partly effective, and none will quickly knock down high populations.
© S. RettkeFig. 4. Five thrips on a tomato leaf
To get the best results, monitor populations and treat when numbers are building but still low. Scout five to ten locations in each field at least once a week. At each location, select five consecutive plants and examine two leaves per plant, for a total of ten leaves. Count the number of thrips on those leaves. Research from North Carolina shows that western flower thrips, the primary vector of TSWV, are more reliably found on leaves rather than flowers. Take action if counts are increasing toward an average of about five thrips per ten leaves. Rotate modes of action as much as possible. Thrips populations tend to be localized, so you are managing resistance within your own fields. The more carefully you rotate products, the more options you preserve. After treatment, continue monitoring to assess efficacy. Some systemic products, such as Beleaf and Verimark, may take several days to up to a week to significantly reduce populations.
Plan ahead when selecting products. Choose insecticides from a variety of IRAC groups to reduce the risk of resistance and prolong effectiveness. Lannate in Group 1A and dimethoate in Group 1B can provide good control, although they are not specifically labeled for thrips in tomatoes and must be used according to all restrictions. Admire in Group 4A is labeled for tobacco thrips and is commonly used to treat transplants before planting. Radiant and Entrust in Group 5 can be excellent where resistance is not present, but resistance is widespread in South Jersey and no more than three applications are allowed per season. Pylon in Group 13 provides excellent control in greenhouse tomato production, but it is not labeled for field use or for very small fruit.
Rimon in Group 15 provides suppression and targets larvae only, with limits on the number of applications per year. Torac in Group 21A offers fair control with seasonal limits. Movento in Group 23 targets larvae and has application limits at the thrips rate. Group 28 products such as Harvanta, Verimark, and Exirel provide fair suppression, with restrictions on total seasonal active ingredient use and limits on the number of applications. Beleaf in Group 29 offers excellent control when applied through drip irrigation and is limited to two applications per year. Incipio in Group 30 is a newer option for 2026 and is also limited to two applications per year. Always remember that the label is the law. Make sure the product is registered for your state and crop, and follow all application restrictions.
Biological insecticides are also available for use in greenhouses, tunnels, and fields. While local efficacy data may be limited, some growers have reported good results in protected culture with products such as Grandevo WDG, LALGUARD M52 OD, and Bronte. These products may require specific storage and handling practices to achieve maximum effectiveness.
In conclusion, a multi-strategy approach is essential for managing thrips and TSWV. Use resistant varieties and preventative practices to reduce thrips populations and limit virus spread. When applying insecticides, base timing on action thresholds, monitor results, and rotate IRAC groups carefully to delay the development of resistance.
Source: Rutgers University
