Page Intro: Metaphycus helvolus is a soft scale parasitoid useful for the prevention and low-infestation management of various soft scales. 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 gold, 1.3 mm. mini-wasps are best used as preventive agents. They can also be used to tackle and maintain minor to heavy infestations of several soft scale species. And, if established, they can adequately protect a planting for a season or, perhaps, more in certain situations.
M. helvolus, which are shipped as pre-emerged adults, are the product of choice when soft scales that can host this parasitoid are present. (These wasps are typically shipped with honeydew substitute or honey on the lid of their jar, but it is provided merely as a moisture source. These parasitoids do eat the stuff, but it is not recommended for supplemental usage at your release site. In fact, too much honeydew at a release site can pose problems — see Advisories.)
Some of the species which can be controlled with these parasitoids include the black scale (their favorite), Mexican black and hemispherical scale insects (Saissetia oleae, S. miranda and S. coffeae, respectively); nigra scale (Parasaissetia nigra); the brown soft and citricola scale insect species (Coccus hesperidium and C. pseudomagnoliarum, respectively); and other economically important species. (Please Note: Brown soft scale control has been debated. Some researchers say it can’t be done. Yet, in several forced situations, I’ve seen them work quite well — even at the University of New Hampshire, where the results were confirmed. I suggest growers perform their own trials.) [Intro]
Life-style
These parasitoids, work by laying eggs inside scale insects. They will lay up to 100 eggs, killing 5 to 25 pests as they do. They will host feed on many more. The wasps’ larvae which hatch from the eggs, slowly weaken and kill the scales from within (endoparasitism). New parasitoids emerge out of the empty scale cadavers after they pupate.
The life-span of these parasitoids is roughly 42 days in their immature stages, then around 2 months as adults. The conditions for optimum performance will be between 73-87°F with relative humidity of around 50%. But these are optimum conditions, and not necessarily a prerequisite of successful implementation. Please note, however, significantly cooler or warmer temperatures and humidity fluctuations may hamper reproduction and development a certain degree. [Intro]
Benefits
These parasitoids, with the right host, in the right conditions, are superb performers.
M. helvolus are superb curative agents, thus offering growers a potential money-saving tool (they can be more economical than pesticides). Additionally, they can establish themselves in many situations. Once established, growers might be able to reduce the size of, or curtail, future releases due to the presence of on-site wasps; another potential money-saver.
Lastly, these parasitoids, being shipped as adults, offer the benefit of fast oviposition or egg-laying, plus a lot of host-feeding. [Intro]
Drawbacks
They won’t overwinter in cold climates; they can be difficult to scout (see Scouting); they are attracted to lights, light colors and sticky traps; and ants and honeydew must be under control. Whew! These drawbacks offer some interesting challenges at times. [Intro]
Fortunately that’s it. Not! One more thing: they’re a bit pricy, too. The latter, though, can be debated by many folks since these mini-wasps have such potential. [Intro]
Scouting
Reduction of pest numbers (empty scales and lack of crawlers) is a sure sign of success. The scout can also usually find scale insect cadavers with an exit hole in them. This is a very positive sign. Trying to spot the wasps themselves, say, two weeks after a release, would be an exercise in futility. A reduction in natural honeydew quantities and clean new growth are other notable indicators of parasitoid success. [Intro]
Advisories
Metaphycus helvolus eat honeydew, but don’t particularly like to get the stuff on them. If honeydew is excessive, these parasitoids will spend most of the time cleaning themselves. Therefore, concentrations of honeydew should be cleaned prior to releasing. This can be accomplished with hot water — as hot as the plants can stand it.
Ants are another serious issue related to honeydew. They must be controlled. Use barrier products or boric acid products to control the ants, if they are a problem.
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 whiteflies, etc., hang them for only two to three days per week. [Intro]
Usages
Greenhouses and interiorscapes are the settings where these parasitoids are most often employed by folks. However, in the right environment, these wasps can be used with great success outdoors. After all, they are reared especially for the California citrus industry. [Intro]
Rates, Instructions, and Purchase
Need more information? Check out our release rates or our short-term storage, handling, and release instructions. These parasitoids aren’t commercially available. [Intro]
