Key takeaways
- Whiteflies are Homopterans, like aphids — widely distributed and capable of millions of dollars in annual U.S. crop damage.
- Two key greenhouse species: greenhouse whitefly (Trialeurodes vaporariorum) and silverleaf whitefly (Bemisia argentifolii) — correct species ID drives parasitoid selection.
- The pupal stage is the most reliable for identification — before releasing biocontrols, ID at least to genus.
- Damage signature: honeydew, sooty mold, chlorotic mottled leaves, and virus transmission (TYLCV and others).
- Preventive go-to controls: Encarsia formosa (for greenhouse whitefly), Eretmocerus eremicus (for Bemisia), Delphastus catalinae for outbreaks, and yellow sticky traps for monitoring.
Whiteflies are tiny Homopteran insects — relatives of aphids — that attack a huge range of vegetable, herb and floral crops. They’re fast to spot but tricky to identify to species, and species ID is the difference between successful biocontrol and a failed release.
Background
Like aphids, whiteflies are members of the order Homoptera. Also like their cousins, they’re widely distributed insect pests — with several species problematic in greenhouse crops. Whiteflies attack a huge range of vegetable, herb and floral crops, causing perhaps millions in damage every year across the United States.
Fortunately, they’re among the easiest pests to detect in the cursory sense — the adults are flighty, visible white insects that take off in clouds when foliage is disturbed. Further identification, however, is essential if you plan to control them biologically.
How They Become a Problem
As temperatures climb in the spring — or much earlier in greenhouses — whiteflies show up. Observant growers usually notice a flitting white insect or two in or around the crop. If this is your situation, act immediately, especially if you haven’t already started a control program. If your approach is biological, you’ll need to know the whitefly identity, at least to genus level.
There’s a small handful of whiteflies that infest greenhouse crops: three species across two genera are usually the troublemakers. Mistaken identity is the most common cause of a failed parasitoid release — if your Encarsia is paired with a Bemisia whitefly, you’ll watch the parasitoids work for weeks with no apparent effect.
A Serious Pest
The whitefly pupal stage is where you can most accurately identify the species. Identification matters because Encarsia formosa, one of the most popular parasitoid biocontrols, prefers the greenhouse whitefly (Trialeurodes vaporariorum) and may take several generations to acclimate to a different genus.
Another popular parasitoid, Eretmocerus eremicus, prefers the B-whitefly species (“B” for Bemisia spp.). Bemisia argentifolii, the silverleaf whitefly, is a major economic pest of poinsettia, tomato and ornamental crops. Eretmocerus can also parasitize greenhouse whitefly, making it a more versatile choice when the species mix is unknown.
Some Advice on Whiteflies
If whiteflies aren’t defeated early — before damaged tissue can be auto-corrected and outgrown — they cause considerable damage to a salable crop. They feed by sucking plant sap, causing leaf spotting, yellowing or interveinal chlorosis. Feeding also produces sticky honeydew, which fosters sugar-feeding ants (which then disrupt your biocontrols) and supports black sooty mold.
Whiteflies also transmit several damaging plant viruses, including tomato yellow leaf curl virus (TYLCV) and squash leaf curl virus. As with thrips, once a virus is transmitted no biocontrol reverses it — the only defense is to keep adult populations below the transmission threshold.
Get the species ID before you place the order. The right parasitoid on the wrong whitefly is a wasted release — and a lost month of crop time.
Scouting Whiteflies on Plants
If you can’t prevent whiteflies through prophylactic releases of the right parasitoid, detect them early while numbers are still low. Yellow sticky traps are useful, but once you begin parasitoid releases, remove or reduce the traps — they catch your beneficials too. Black and yellow E. formosa may be visible on the traps; the all-yellow E. eremicus tends to disappear into the background.
Direct foliar scouting — turn leaves and look at the undersides — gives you adult count plus pupal density. The whitefly pupal case stays on the leaf after the adult emerges, so old pupal cases at a given density tell you the previous generation’s pressure.
Yellow traps and parasitoids don’t mix
Whitefly parasitoids (small wasps) are strongly attracted to yellow. If you’re running an Encarsia or Eretmocerus program, switch from yellow sticky cards to population counts on randomly selected plants after your first parasitoid release. Save the traps for spot-checking suspect hotspots.
Some Solutions for Whitefly Control
If numbers begin to climb, vacuuming up the adults when plants are disturbed is a sound mechanical strategy. Other biocontrols better suited to taking down larger numbers — like the whitefly-predatory beetle Delphastus catalinae (formerly D. pusillus) — can be deployed alongside the parasitoids.
The classic curative tools are Encarsia formosa for greenhouse whitefly and Eretmocerus eremicus for Bemisia. Both are best used preventively on weekly schedules during susceptible-crop stages. Screening can also prevent whitefly establishment, especially when you don’t know which species you’ll have.
Horticultural oils, neem oil and insecticidal soaps work as foliar knockdowns — rotate them carefully if you’re running parasitoid releases, because soaps and oils will also kill the wasps and their hosts indiscriminately.
For over 30 years, Green Methods has been a leader in the production and application of beneficial organisms used in biological pest control and integrated pest management programs.