Authors: Julia Dubeau (Research Assistant, OMAFA), Rose Labbé, PhD (Research Scientist, Greenhouse Entomology, AAFC), and Cara McCreary (Greenhouse Vegetable IPM Specialist, OMAFA)
Meet the Creature
For this Creature Feature, we’re meeting Nesidiocoris tenuis, commonly known as Nesi, green bug, or tomato bug.
Nesi is a small green mirid bug that has become a concern for Ontario greenhouse vegetable growers – specifically greenhouse tomatoes and greenhouse cucumbers but greenhouse peppers are also a potential host.
At first glance, Nesi might not look too scary. It is small, green, and easy to mistake for something helpful. But this is one of those “don’t judge a bug by its colour” situations — not every green bug in the crop is a good bug!
Nesi is an omnivorous mirid, meaning it can feed on both insects and plant tissue. In some regions around the world, it has been used as a beneficial insect, but in Ontario greenhouse vegetable production it is considered a pest because of the plant damage it can cause.
Friend or Foe?
For Ontario greenhouse vegetable growers, Nesi is a foe.
This can be confusing because Nesi has a mixed reputation. While it can feed on other insects, it also feeds directly on plants. In Ontario, the concern is that populations can build quickly in greenhouses during summer conditions and the resulting plant feeding damage can become an economic issue.
Nesi can also be confused with other mirid bugs, such as Dicyphus hesperus, which is a beneficial mirid used as a biocontrol agent.
Because these insects can look similar, it is important to confirm the ID before deciding whether action is needed. For more information on distinguishing between common mirid species, see the Mirid Identification Resources and Printable Scouting Sheets.
Why Growers Care
Growers should care about Nesi because both nymphs and adults can feed on plant tissue. All stages can be damaging, although 5th instar nymphs and adults are considered the most damaging.
punctures, scars, or stippling on the fruit surface.
forming on stems and young plant tissue.
The type of damage depends on the crop.
Greenhouse tomatoes
- Necrotic lesions and rings on stems and young plant tissue
- Damage on leaf petioles
- Damage on inflorescences
- Punctures, scars or stippling on fruit
Greenhouse cucumbers
- Punctures in new or emerging leaves
- Necrosis on pedicels and inflorescences
- Punctures on fruit
- Stippling in leaves and fruit
Greenhouse peppers
- Punctures in pedicels
- Damage on leaf petioles
- Punctures on fruit
- Stippling on stems and fruit
This feeding damage can affect plant health, fruit quality and marketability. It can also be easy to miss at first, especially when populations are low or damage is limited to certain areas of the crop.
Damage risk tends to increase when there is low prey availability, a higher Nesi population and warmer temperatures. Nesi is frequently observed causing a lot of plant damage in summer conditions even when prey populations are high. (Maybe this heat makes them grumpy!)
Where to Look
When scouting for Nesi, focus on newer growth and areas where the bugs may hide or feed.
Good places to check include:
- Under leaves
- Around stems
- Newer growth
- Suckers
- Flowers
- Fruit and fruit clusters
- Petioles
- Pedicels
In tomatoes, pay particular attention to growing points, suckers and fruit (check suckers and fruit especially after topping).
In cucumbers and peppers, look for punctures and stippling on leaves, stems, flowers, and fruit.
Nesi populations can build quickly in greenhouses during summer conditions and damage is often associated with warmer temperatures.
What It Looks Like
Nesi adults are small green mirid bugs, about 5–10 mm long.
Key features to look for include:
- Green body
- Dark brown eyes
- Black band at the base of the head
- Black “knees”
- Black first and second antennal segments
- Black spots on the wings
Nymphs are smaller than adults and do not have fully developed wings.
Because Nesi can look similar to other mirids, colour alone is not enough for identification. A green mirid could be a pest or a beneficial insect, so it is important to look for the distinguishing features.
Monitoring
The first management step is proper identification. Since Nesi can be confused with beneficial mirids, growers and scouts should confirm what they are seeing before deciding what action is needed.
Useful monitoring steps include:
- Scout regularly for both insects and damage
- Check under leaves, around stems, and on newer growth
- Look closely at suckers and fruit, especially in tomatoes after topping
- Watch for punctures, stippling, necrotic lesions, and flower or inflorescence damage
- Record where insects and damage are found
- Track whether the population is localized or spreading
- Use Nesi scouting sheets for tomatoes, cucumbers, and peppers
- Use mirid identification resources to help separate Nesi from beneficial mirids
- Check Dicyphus hesperus banker plants carefully, as Nesi may establish where mirid-friendly habitat or prey sources are present
Management
Management should focus on reducing the chance of Nesi populations building and spreading in the greenhouse.
Cultural and physical management strategies include:
- Remove plant debris and weeds that may harbour Nesi eggs or nymphs
- Remove suckers from the greenhouse after pruning – they likely contain eggs and may increase the chance of reinfestation
- Install insect exclusion screening on vents where appropriate (maxaximum of 0.8 x 0.8 mm)
- Use large dry sticky cards or tape to help monitor or trap adults
- Continue checking Dicyphus hesperus banker plants and nearby crop areas for possible Nesi establishment
There is also an emergency use registration for PYGANIC® insecticide for management of Nesi on greenhouse-grown tomatoes and cucumbers in Ontario. The registration allows use in Ontario from April 17, 2026 to April 16, 2029. This should be treated as a registration notice, not a product recommendation.
If chemical control is being considered, always check the current label before use. PYGANIC® can be toxic to bees and other beneficial arthropods, including predatory and parasitic insects, spiders, and mites, which is an important consideration in greenhouse IPM programs. For more information on this registration, see the PYGANIC® emergency use registration notice or visit the PMRA label site for a copy of the minor use label.
Main message:
If you find a green mirid in the crop, do not assume it is beneficial. Confirm the ID, check for damage, and keep track of whether the population is spreading.
For more information on Nesi in greenhouse tomatoes, visit the Ontario Crop IPM page for Tomato bug/Green bug/Nesi.