Andy Wyenandt

Tomato spotted wilt virus (TSWV) has caused significant problems for some fresh-market tomato and pepper growers in New Jersey the past few growing seasons. Although not uncommon, economic losses these past few years have been extensive.

TSWV is vectored by various species of thrips, a common vegetable insect pest that seems to be on the incline and very difficult to control in vegetable production throughout the state. The most important vector of TSWV is the western flower thrips, Frankliniella occidentalis. It’s mode of transmission is persistent propagative, meaning that thrips nymphs have to feed on a TSWV-infected plant, whereby followed by a short incubation period (lasting from hours to days), the virus is then persistently transmitted throughout the rest of the insect’s life span.

Importantly, TSWV cannot be passed from infected females to eggs; and TSWV is not transmitted in seed.

The western flower thrips and TSWV both have a wide host range! Western flower thrips host range includes: tomato, pepper, onion, celery, cucumber, lettuce, potato, basil, strawberry; a wide range of herbaceous ornamentals (e.g., impatiens, geranium, marigold, petunia, dahlia, gerbera daisy, carnation) as well as many common weeds (e.g., pigweed, chickweed, lambs quarter, thistle, galinsoga). TSMV can infect over 1,000 plant species from more than 90 plant families.

In 2022, samples of a TSWV-infected fresh market tomato variety with Sw-5b resistance were collected in southern New Jersey and sent for analysis. Results determined that RB (C118Y) TSWV was present in the state; and the strain found in New Jersey was similar to the RB TSWV found in fresh-market tomato from Mexico and processing tomato in California suggesting a high potential for its widespread movement. Since 2022, isolated cases of RB-TSWV have been found in New Jersey each growing season.

So, where do we go from here? Based on the isolated reports of TSWV being found on resistant fresh-market tomato in New Jersey the past few growing season, it does not appear that RB TSWV is currently widespread throughout the state. However, this may likely change.

All vegetable growers, those who produce their own transplants or bring them in, need to carefully evaluate their thrips monitoring and mitigation programs this winter and spring.

1. Start fresh. Prior to the transplant production season, clean and disinfect the greenhouse or any other structure where you might be holding transplants. Remove any weeds within and around the structure. Use sticky cards to monitor the potential carryover thrips population during the winter months, especially if you have any plant material in the greenhouse during those months.
2. Never produce or keep tomato or pepper transplants you start yourself or bring in, in the same greenhouse with any ornamental plants.
3. Segregate any transplants that are brought into your operation from your own transplants, as well as segregate different source of transplants as best you can.
4. Evaluate all incoming transplants for thrips damage.
5. Treat all incoming transplants with an insecticide immediately.
6. Use yellow sticky cards to continually monitor for thrips populations in the greenhouse from the start of the transplant season until the end.
7. Consider using biological or natural control(s) in the greenhouse.
8. The use of silver reflective mulches have been shown to reduce thrips populations in fields.
9. Develop a season-long insecticide program prior to the production season; from applying an insecticide at transplanting through cover sprays until harvest.
10. Monitor thrips populations and feeding damage in the field with regular scouting and sticky cards.
11. Closely monitor thrips feeding injury on pepper and tomato fruit during the production season.
12. Proper weed control is essential since many weeds may harbor the virus or infected thrips. This includes areas around the production field.
13. Rogue out any suspicious looking plant(s) prior to transplanting, or any suspicious looking plant early in the production season (e.g., any plant that starts to stunt out early) to help mitigate the within field spread.

Growers should continue to utilize TSWV-resistant tomato and pepper varieties realizing the effectiveness of those in limiting TSWV is becoming compromised. All growers need to continue to follow best management practices (such as those listed above) and pay careful attention to current weaknesses in their production practices and thrips control programs and adjust their management practices heading into 2026 growing season.

If you suspect RB-TSWV in transplant production or the field later this year please contact your county agent.

by: Andy Wyenandt, Maria Cramer, and Amanda Quadrel

References:

Macedo MA, Melgarejo T, Cespedes M, Rojas M, Lazicki P, Turini T, et al. (2024) An all-out assault on a dominant resistance gene: Local emergence, establishment, and spread of strains of tomato spotted wilt orthotospovirus (TSWV) that overcome Sw-5b-mediated resistance in fresh market and processing tomatoes in California. PLoS ONE 19(7): e0305402.

Tomato spotted wilt virus on pepper and tomato. Inga Meadows and Andy Cooper, NCSU 2024

Gautam et al., 2022. First report of a resistance-breaking strain of tomato spotted wilt orthotospovirus infecting Capsicum annuum with Tsw resistance gene in Texas. Plant Dis. 107:1958.