Overview:

Poinsettia has been successfully grown using Biological controls for over 15 years in North America and Europe. The major pest associated with the Poinsettia is Whitefly. Plants propagated in tropical regions can be infested with Bemisia or Sweet Potato Whitefly, which makes international movement difficult because it is an undesirable pest. Other pests, such as Thrips are, at this point in time, not very interested in Poinsettia. Lewis mite, a small insidious mite can be a problem, but can easily be controlled by Amblyseius fallacis, if applied as a preventative.

Propagation:

Young seedlings, cuttings, or tissue culture plants should be inoculated with Gaeolaelaps gillespiei or Hypoaspis miles as soon as they are in the growing media. They both can be applied overhead using a hand spreader, shaken onto the flats, or premixed right into the soil mix provided it is used up the same day.
One week after introduction of G.g. or H.m., nematodes should be watered in at the recommended rate. The nematodes ensure an effective knock-back of the fungus gnats and also feed and help disperse the soil mites.
Rates for both mites are 100 mites per square meter
Whitefly must be assessed accurately by closely inspecting the cuttings for eggs. It should be assumed that the propagator very vigorously treated the cuttings against adult whitefly. This assumption precludes the use of beneficials against whitefly during the first month of propagation due to the residual pesticides.

Main Crop:

Re-apply Hypoaspis or Gaeolaelaps at the transplanting stage at the same rate (100 per square meter) and also repeat the nematode application one week later. Fungus gnats should be monitored using yellow sticky traps. The larvae should be regularly monitored by applying a slice of raw potato to the surface of the soil. Leave it there for a set period of time eg. overnight (12 hours), then remove and inspect. The larvae are attracted to the potato. Increasing numbers suggest a developing problem, while decreasing numbers show control. Fungus Gnats should not be tolerated as they reduce the root development of the young plants and the flying adults are capable of transporting pest mites, such as Lewis mite.
Whitefly prevention is a multipronged attack. Bemisia is not easily scouted or monitored. Unless you are prepared to pick up every plant, it is best to assume that Bemisia eggs survived the propagator’s treatment, and begin introductions of Delphastus catalinae, after a suitable waiting period to ensure that the residuals of the propagator’s treatment are gone. Three staggered introductions, each two weeks apart, of 0.1 beetles per square meter should be done. Some beetles should be placed near known infestations, but most should be neutrally released, ensuring aggressive searching. Delphastus find Bemisia and all other whitefly by smell, greatly preferring Bemisia. Once Delphastus has eliminated the Bemisia they will turn to other whitefly species.
Even if the plants appear clean of Greenhouse Whitefly, begin weekly introductions of fresh Encarsia at a rate of 0.25 per square meter per week. Any detectable level of Greenhouse Whitefly should increase the Encarsia rate to at least 1 per square meter, weekly. We do not recommend any other parasitoids other than fresh Encarsia, as the lower growing temperatures are not suitable for them, or stored Encarsia.
We have had considerable success using Monitoring/Trap/Banker plants in Poinsettia for Greenhouse Whitefly. The best plant to use is Eggplant. The Eggplant is also more effective in attracting Thrip and aphids. The trap plants should be placed throughout the crop, 1 per 1000 square meters. The trap plants will help in monitoring, as the pests will show up in these plants first. They can be valuable as an actual trap, if they are vacuumed on a daily basis using a “Dust-buster”. Make sure that the vacuum is frozen overnight to kill the pests. By focusing the Benefical insects on these plants, they will become effective banker plants, generating your own crop of Benefical insects.
As aphids now appear to be ready to move onto any crop, they should be anticipated. Any sign of aphids should be reacted to by weekly introductions of Aphidoletes aphidimyza at a rate of 3,000 per hectare. Continue until all of the aphids are gone.
Thrips in Poinsettia seldom result in economic damage. Thrips, however, have proven to be a new pest in many crops, so, careful management is necessary. Having H.m. or G.g. in the soil will prevent WFT from cycling, as the soil mites are very effective in predating the pupating Thrip larvae. Trap plants, such as Yellow Hero Marigold, are very effective in Poinsettia. If Thrip damage is being seen, apply Amblyseius cucumeris at a rate of 50 to 500 per square meter, every 3 to 4 weeks.
Lewis mite is very hard to detect until it is too late. If you have a history of Lewis mite, or you have reason to suspect that Lewis mite has come in on the cuttings, apply Amblyseius fallacis at a rate of 20 mites per square meter, just once, after the plants are transplanted, but before they are finally spaced.

Finishing Off:

Because the light level drops so dramatically, any pests still established will suddenly get a reprieve. It is very important to have a clean crop prior to the light level decrease. If you are still working on Whitefly, switch to only Delphastus. If you are still working on Lewis mite, switch to only cucumeris. If you are having trouble with Aphids, switch to Aphidius matricariae, or, if in Canada, the Brown Lacewing.