Aphid Control with Aphidius & Aphelinus parasites

Description

Aphidius colemani, Aphidius ervi and Aphelinus abdominalis are all natural aphid parasites and very useful and effective for the prevention and low-infestation management of various aphid species. These 2-3 millimeter 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.

<em>Aphidius colemani</em> adultAphidius colemani, which are normally shipped as ready-to-emerge mummies (expect to see some hatched adults on arrival), 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. But it will also attack the green peach aphid (Myzus persicae), the tobacco aphid (Myzus nicotianae) and the bird cherry-oat aphid (Rhopalosiphum padi) commonly used on banker plants.

Aphidius ervi, which are normally shipped as adults, seem to be the product of choice when the potato aphid (Macrosiphum euphorbia) and the glasshouse potato aphid (Aulacorthum solani) are present. However, as it is with the other Aphidius spp., many other hosts (such as Myzus spp, Sitobion spp, Schizaphis spp, Rhodobium spp and Acyrthosiphum spp) are subject to parasitism.

Parasitized aphidsAphelinus abdominalis, which are normally shipped as ready-to-emerge mummies, should be used when targeting the potato aphid (Macrosiphum euphorbiae) and the widely distributed glasshouse potato aphid (Aulacorthum solani). Aphelinus prefers to parasitise second and third instar aphids. Larger aphids are less frequently attacked, while first and small, second instars are used as a source of food by the adults. This host feeding is an important source of mortality in the aphids, with each female Aphelinus abdominalis killing approximately 2 aphids per day. By host feeding, the parasite obtains a source of proteins, which allows it to continue development of eggs and to increase the total number of offspring it produces. In laboratory studies, each female is capable of producing an average of 250 or more offspring over a period of 3 weeks, with an average daily production of 14. Egg laying continues throughout the life of the female.

Lifestyle

Parasitized aphidsThese 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.

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. 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 climates. Once established, growers might be able to reduce the size of releases made due to the presence of on-site wasps: another money-saver.

Scouting

Emergence-hole comparisonTo determine if more Aphidius spp. wasps or hyperparasites are emerging out of your mummies, 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. 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.

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. 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.

Usages

Greenhouses, fields, interiorscapes, orchards and gardens. We’ve seen the successful preventive and curative implementation of these species in just about every conceivable situation.

Release Rates for Aphidius colemani

ClassificationRelease Information
Preventative1-5 per 100 square ft., weekly
Hot spots5-25 per 100 square ft., weekly

Release Rates for Aphidius ervi

ClassificationRelease Information
Preventative1-5 per 100 square ft., weekly
Hot spots5-25 per 100 square ft., weekly

Release Rates for Aphelinus abdominalis

ClassificationRelease Information
Preventative2-5 per 100 square ft., weekly
Hot spots10-25 per 100 square ft., weekly

Release Rates for mixed Aphidius/Aphelinus bottles

ClassificationRelease Information
Preventative1 per 10 square ft., weekly as needed
Hot spots5 per 10 square ft., weekly as needed

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