Tomato is the crop where Encarsia formosa made its name. UMass Extension describes the whitefly parasitoid as most effective in long crops grown for more than four months, such as tomato and cucumber. Aphids, spider mite and leafminer also have natural enemies that work in a tomato house. Start the whitefly and aphid parasitoids early, and release the spider mite predator at the first mites found.
Tomato is also a harder crop for predators than cucumber or pepper, because its leaves and stems are covered in glandular hairs. Koppert says not to use Amblyseius cucumeris in tomato. Cornell calls it usually ineffective there, and UConn lists the Swirski mite and Orius as unsuitable on greenhouse tomato. Western flower thrips and tomato russet mite therefore have no reliable release on this crop. Vent screens, clean transplants and early scouting do that job instead.
The usual whitefly on greenhouse tomato; honeydew and sooty mould foul the fruit. Encarsia searches poorly on very hairy varieties.
Causes irregular ripening and carries tomato yellow leaf curl virus. Confirm the species first: Encarsia is most effective against greenhouse whitefly, and Eretmocerus is the parasitoid used for this one.
UC IPM rates it the more damaging aphid on tomato. Aphidius colemani cannot develop in it, so use A. ervi.
Moves into young plants early and carries alfalfa mosaic virus. UC IPM says it seldom needs treating on tomato by itself.
Tomato's glandular hairs slow the predator down, so release early, concentrate on the infested plants and check a week later that it has spread.
Matters on long-season tomatoes. Broad-spectrum sprays aimed at other pests kill its parasites and set off outbreaks.
The risk is tomato spotted wilt virus. The foliar predators fail on tomato, and the soil mite only takes pupae in the growing medium, so screens and roguing matter more.
Bronzing climbs from the base of the plant. No sold predator has proven itself on tomato yet, and sulfur is the standard control.
| J | F | M | A | M | J | J | A | S | O | N | D | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Greenhouse whitefly | Jan: Building | Feb: Building | Mar: Building | Apr: Building | May: Building | Jun: Pest pressure high | Jul: Pest pressure high | Aug: Pest pressure high | Sep: Pest pressure high | Oct: Pest pressure high | Nov: Building | Dec: Building |
| Aphids | Jan: Quiet | Feb: Quiet | Mar: Quiet | Apr: Building | May: Pest pressure high | Jun: Pest pressure high | Jul: Pest pressure high | Aug: Building | Sep: Building | Oct: Building | Nov: Quiet | Dec: Quiet |
| Spider mite | Jan: Quiet | Feb: Quiet | Mar: Quiet | Apr: Quiet | May: Building | Jun: Pest pressure high | Jul: Pest pressure high | Aug: Pest pressure high | Sep: Pest pressure high | Oct: Quiet | Nov: Quiet | Dec: Quiet |
| Western flower thrips | Jan: Quiet | Feb: Quiet | Mar: Quiet | Apr: Building | May: Pest pressure high | Jun: Pest pressure high | Jul: Pest pressure high | Aug: Pest pressure high | Sep: Building | Oct: Building | Nov: Quiet | Dec: Quiet |
| Tomato russet mite | Jan: Quiet | Feb: Quiet | Mar: Quiet | Apr: Quiet | May: Quiet | Jun: Building | Jul: Pest pressure high | Aug: Pest pressure high | Sep: Pest pressure high | Oct: Building | Nov: Quiet | Dec: Quiet |
A starting point for a first season, assuming the house has no residual insecticide and no resident pest populations. The parasitoids go in from planting and continue for as long as the crop is in. Adjust the rates to your own scouting counts and your supplier's advice.
Most of what decides a release program is the house itself: what was sprayed, the climate, and what gets in through the vents.
Broad-spectrum insecticides kill the parasitoids, and UC IPM notes that leafminer outbreaks often follow sprays aimed at other pests. Check the products against the compatibility matrix before the first release.
UC IPM gives 0.355 mm (355 microns) or finer to keep out winged aphids, and 0.145 mm or finer for western flower thrips. Fine screen restricts airflow, so add screen area or adjust the ventilation.
Encarsia works best at 70–80 °F (21–26 °C) and 50–80 % relative humidity (UMass, UConn). Phytoseiulus reproduces best at 60–90 % humidity and retreats down the canopy in hot, dry air (K-State).
Tell greenhouse whitefly from silverleaf by the pupae before choosing a parasitoid. Take yellow sticky cards down before each Encarsia release, and leave the lower leaves on until the wasps have emerged from the black scales.