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.
Aphidius 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) and the bird cherry-oat aphid (Rhopalosiphum padi).
Aphidius 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 (such as Myzus spp, Sitobion spp, Schizaphis spp, Rhodobium spp and Acyrthosiphum spp) are subject to parasitism.
Aphelinus 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 so 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.
These 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.