Page Intro: Aphidius spp., A. colemani, A. matricariae, and A. ervi are all aphid parasitoids and very useful and effective for the prevention and low-infestation management of various aphid species. 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 2-3 mm. mini-wasps are best used for preventing the establishment of more than 40 species of aphids. They can also tackle light to medium infestations. And, if established, they can adequately protect a crop throughout the season, with some possible exceptions in late summer (see Drawbacks).
A. colemani, which are normally shipped as ready-to-emerge mummies, seem to be the product of choice when melon or cotton aphids (Aphis gossypii) are present as these are typically the aphid species on which they are reared.
A. matricariae, which are normally shipped as pre-emerged, pre-fed adults, are the product of choice when aphids other than A. gossypii are present. Some popular hosts of this mini-wasp include: the bean aphid (Aphis fabae), potato aphid (Macrosiphum euphorbia); the pea aphid (Acyrthosiphon pisum); and the green peach aphid (Myzus persicae), probably the most common aphid and the species on which they are reared.
A. ervi, which are normally shipped as adults, seem to be the product of choice when the potato aphid (M. euphorbia) and the glasshouse potato aphid (Aulacorthum solani) are present. However, as it is with the other Aphidius spp., many other hosts are subject to parasitism. [Intro]
Life-style
The Aphidius spp., as parasitoids, work by laying eggs in aphids. And they can lay 200-300 eggs! The wasps’ larvae which hatch from the eggs, slowly weaken and kill the aphids from within (endoparasitism). The aphids then turn into “mummies” as the wasps pupate. The life-span of these parasitoids is roughly 2 weeks in their immature stages, then 2 weeks as adults. The conditions for optimum performance will be between 64-75°F with a relative humidity of around 80%. 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 wasps will work in fairly cool areas with a low light levels and a short photoperiod. Moreover, they are really easy to scout (see Scouting). One additional benefit: it is very common to hear reports of these aphid parasitoids returning the following year(s).
Aphidius spp. wasps are superb preventive agents, thus offering growers a potential money-saving tool. Additionally, they can establish themselves in nearly any region of the country; they overwinter in the toughest climes. Once established, growers might be able to reduce the size of releases made due to the presence of on-site wasps: another money-saver.
A. matricariae, because they are shipped as pre-mated adults, offer the benefits of a high female sex ratio of 95:1, fast oviposition (or egg-laying, I’ve seen it happen in as little as 10 mins.) and freedom from hyperparasites (see Drawbacks, next). [Intro]
Drawbacks
One thing to consider when using some Aphidius spp. is the potential of hyperparasites. These even smaller wasps parasitize the Aphidius spp. while in the aphid. So instead of another Aphidius spp. emerging, the hyperparasite will emerge in its place. This can be very disruptive to your biocontrol program. For this reason, ordering adult parasitoids when possible is recommended, especially in late summer when the A. colemani mummies might be contaminated. Please note, however, it has been suggested that too much emphasis might be placed on the potential of getting hyperparasites. Due to modern production processes, getting hyperparasites with your A. colemani order is extremely rare. Once they’re on site, though, anything can happen. Nevertheless, A. matricariae and A. ervi can develop this problem once released at your site, too, especially in the late summer (see Scouting, next). In addition to the rare problem of A. colemani being shipped with hyperparasites, because they are mummies, their sex ratio and emergence rate cannot be accurately predetermined, plus they must feed and mate prior to oviposition. The latter may cause a lag in the performance schedule. Scouting may be somewhat hampered because the use of yellow sticky traps as a monitoring tool may be hampered (see Advisories). [Intro]
Scouting
To determine if out of your mummies are emerging more Aphidius spp. wasps or if hyperparasites are emerging, take a close look at the exit hole. The emergence of the Aphidius spp. wasp produces a clean, round hole without jagged edges. And often the flap or lid of removed material is absent. Scouts have the obvious mummies and exit holes to look for, but with these agents, there will probably be some visible and nearly instant reduction in the pest count. When Aphidius spp. are released, aphids often send a scent signal of alarm. We’ve actually seen them falling from a plant trying to flee. An additional sign of parasitism — early parasitism — and Aphidius spp. activity in your crop is the tiny dark-orange to reddish/brown oviposition [sting] mark which may be present on the back-end to top of the aphids — on the abdomen. Just prior to the wasp pupating, its host aphid will turn a grayish color. This, however, depends upon the host species. [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 whiteflies, etc., hang them for only two days per week. Ants, if present, should be controlled. They will defend aphids from predators and parasites to protect their honeydew food (the excrement of aphids, yuk). Use barrier, exclusion 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. [Intro]
Usages
Greenhouses, fields, interiorscapes, orchards and gardens. I’ve seen the successful preventive and curative implementation of these species in just about every conceivable situation. [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 A. colemani, purchase A. matricariae (now available seasonally only), or purchase A. ervi. [Intro]
