Page Intro: Encarsia formosa, specifically the greenhouse whitefly parasitoid, is a well-tested for the prevention and low-infestation management of greenhouse whiteflies. On this page you will find a description, life-cycle info, benefits, drawbacks, scouting info, advisories, usages, and other good stuff such as ordering.
Description
These 0.7 mm. mini-wasps are best used for preventing the establishment of the greenhouse whitefly (Trialeurodes vaporariorum). They can also tackle minor to medium infestations. And, if established, they can adequately protect a crop throughout the season. In addition to the greenhouse whitefly, E. formosa can parasitize a few other whitefly species, the sweet potato whitefly (Bemisia tabaci), for example. Acceptable prevention and control of other whitefly species, however, is effectively unobtainable with E. formosa and I do not recommend their use for this purpose. (For those species, use Eretmocerus eremicus.)
Encarsia formosa are supplied as pupae protected in the greenhouse whitefly scales (pupae) which they had used as a host, and actually still are. These parasitized scales are adhered to a small card which can be hung in the plants. The cards come in perforated strips of ten; equal to 1000 E. formosa. And when we say 1000 parasitoids, we mean 1000 hatching wasps, not just 1000 pupae (not all will hatch). E. formosa are also available as loose parasitized scales supplied in a small shaker. For this product I recommend some form of distribution boxes or small cups which can be secured in the crop. [Intro]
Life-style
Encarsia formosa, as parasitoids, work by laying eggs in the 2nd through 4th immature whitefly stages. The wasps’ larvae which hatch from the eggs, slowly weaken and kill the developing whiteflies from within (endoparasitism) causing noticeable changes upon pupation (see Scouting). And each female wasp (they’re all females by the way) can do this up to 200 immature whiteflies! The life-span of these parasitoids is roughly 3 weeks in their immature stages, then up to a month as adults. The conditions for optimum performance will be between 68-77°F with a relative humidity of 70% or less. But these are optimum conditions, and not necessarily a prerequisite of successful implementation. Please note, however, cooler temperatures will hamper reproduction and development a certain degree. For example: these wasps won’t fly when temperatures are below 62°F (see Drawbacks). [Intro]
Benefits
They’re very effective preventive agents capable of small-scale control as well. Consequentially, between their low price and resulting prevention, a lot of money can be readily saved, plus a lot of headaches and plant damage avoided. Moreover, they are really easy to scout (see Scouting). And they’re a great part of an IPM program, with quite a few pesticide tolerances. There is a lot of information out there about these parasitoids. Combined, growers probably have a thousand years or more of experience with these mini-wasps. There are certainly a lot of success stories from my contacts (see Drawbacks, next). [Intro]
Drawbacks
Then again, some of our customers have a poor or mediocre results, which, of course, is true of all biocontrol agents. If you follow the numbers (see Rates), though, and what pests you’re actually dealing with, your story should be one of success. They can’t fly below 62°F, but we’re not sure what kind of drawback this really is. As long as daytime temperatures are high enough, you’ll be okay. But then again, there will probably be times when the temperatures are down for one reason or another. Perhaps this should be listed in Advisories instead of under Drawbacks. These wasps are also temperamental about light levels (see Advisories). Honeydew levels, if high enough, can interfere with their performance. A couple of different things can play a role (again, see Advisories). [Intro]
Scouting
The scales or pupae of the greenhouse whitefly turn jet black when parasitized. This is a great indicator. The scales of the Bemisia tabaci turn tan-brown when, on occasion, they, too, become a host to E. formosa. Yellow sticky traps might not be able to be used at times (see Advisories). [Intro]
Advisories
Yellow sticky traps should be removed prior to releasing these mini-wasps. To monitor for thrips, use blue traps. If yellow traps must be used for fungus gnats, etc., hang them for only two days per week. To reduce adult whitefly levels, fast, instead of placing about a million sticky traps up, Suck ‘em up!
Ants, if present, should be controlled. They will defend whiteflies from predators and parasites to protect their honeydew food (the excrement of whiteflies , yuk!). Use barrier products or boric acid products to control the ants. If your planting doesn’t have any ants, check to be sure that the honeydew isn’t too heavy. This may prove to be a hindrance to the parasitoids’ performance; they may spend too much time cleaning themselves. Washing the plants with soap and water — at the highest possible pressure — may help reduce the amount of honeydew. In order for E. formosa to be effective, the release site must be brightly lit, with a minimum of 650 footcandles. Photoperiod or day-length doesn’t seem to be of importance, just intensity. By the way, the required light-levels are achieved in normal greenhouse conditions — on a sunny day.
Some crops, due to their excessive whitefly susceptibility, may require special IPM attention, higher release rates and/or more frequently scheduled releases (closer intervals). Greenhouse tomato production is one example, at least according to a couple of our contacts who’ve suggested I increase the rates for their crop — they felt it was necessary. Another example of a highly susceptible plant would be the eggplant, but it might be used to your favor as a place to harbor and maintain your good guys. A banker plant. [Intro]
Usages
Most greenhouse crops and brightly lit interior situations. I’ve seen the successful preventive and light curative implementation of these species in nearly every qualifying situation. I do not recommend the outdoor use of E. formosa, with possible exception to small-scale use. [Intro]
Rates, Instructions, and Purchase
Need more information? Check out our release rates or our short-term storage, handling, and release instructions. You may also purchase E. formosa cards, or as loose pupae. [Intro]
