Description
Aphidius species are a group of native parasitic wasps, frequently found parasitizing aphids in greenhouses and outdoor crops. Adults are tiny, dark colored, non-stinging wasps up to 1/8 inch long (2-3mm). Larvae develop entirely inside host aphids, which eventually become rigid mummies when the larvae pupate. Aphidius is an outstanding searcher and can locate new aphid colonies even when aphid populations are low. Species include Aphidius colemani, Aphidius ervi and Aphidius matricariae.
Target Pest
Aphidius colemani targets green peach aphids (Myzus persicae), cotton/melon aphids (Aphis gossypii) and cannabis aphids (Phorodon cannabis) and other smaller aphids.
Aphidius ervi targets potato aphids (Macrosyphum euphobiae), foxglove aphids (Aulacorthum solani) and other larger aphids.
Aphidius matricariae targets green peach aphids (Myzus persicae), tobacco aphids (Myzus persicae nicotianae) and many more.
Life Cycle
A complete life cycle takes 10 days at 77°F and 2 weeks at 70°F. Sex ratio in the population is about equal, although there may be slightly more females than males (50-60% females).
Each female lays about 100 eggs in aphids, but may attack 2 to 3 times that many in the process. The larvae develop entirely inside the aphids and do not kill their host until the wasp larva is ready to pupate. The larvae pupate inside the aphid's body, which becomes a rigid, leathery, golden brown mummy. Adults emerge from the mummies by cutting an exit hole in the top. The empty mummy remains on the leaf surface. The size of the adult parasite and the number of eggs it can lay depends on the size of the aphid from which it emerged.
Monitoring Tips
Use a 10-15x lens to inspect aphid mummies for round holes in the hind end, which indicates the adult parasites have emerged. A ragged emergence hole, in the top (mid back) of the mummy indicates a hyperparasite has emerged.
Use in Biological Control
Aphidius species can control many types of aphids, however aphid ID is critical in choosing the best Aphidius for the job.
Optimum conditions are daytime temperatures of 64-77°F and relative humidity 60-80%. Aphidius is not affected by short-day conditions, so it can be used year round.
Aphidius alone will not provide control when aphid populations are high, but can be used with Aphidoletes and lady beetles to provide control. Effectiveness may be reduced in late summer when Aphidius may be attacked by naturally occurring parasitic wasps (hyperparasites).
Product Information
Aphidius is shipped either as parasitized aphid mummies (pupae) from which adults will emerge, or as newly emerged adults. The advantage of shipping adults is that they usually arrive pre-mated and the supplier can ensure they are sent without hyperparasites. Adults should be released immediately by walking along the rows and allowing them to naturally fly out of the container. If necessary, parasitized aphid mummies may be held at 39-50°F for up to 3 days.
Introduction Rates
Aphidius is most effective when aphid populations are low. Parasites can be introduced at low rates before aphids are detected in greenhouses or when aphids are likely to move onto crops outdoors. When aphids have been detected in a crop, higher release rates should be used over a period of at least 3 weeks.
Because of the time it takes for larvae to develop inside aphid mummies, use at least two releases one week apart to establish overlapping generations of the parasite. Most of the parasitized aphids leave the plant before mummies are formed and it has been found that if 10% of aphids found on leaves are mummies, that the population should soon collapse (Ramakers, 1989).
General Rates 1-5/100 ft² or 10-25/100 ft² for high infestations, weekly or as needed.
Pepper Rates - 400 Aphidius/acre or if aphids are established 2,000 Aphidius/acre 2-3 times or until 10% of aphids on plants are mummies.
Tomato Rates - 1 Aphidius/10 plants, weekly for 2 weeks.
Cucumber Rates - 1 Aphidius/plant, weekly.
Ornamentals and Outdoors - 0.1 - 3 Aphidius/10ft² or 0.1-5 Aphidius/plant, weekly or until control is evident.
Note: In gardens, wash high populations of aphids from plants with a strong spray of water before introducing the Aphidius. It always helps to knock down the population as much as possible as beneficials work best preventatively.
Using Chemicals
Aphidius is likely sensitive to chemical residues found on plants and greenhouse surfaces. Growth regulators used in crop production should not be harmful to Aphidius. Spreader-stickers are likely to be harmful to Aphidius on contact, but do not have residual effect. Insecticidal soap can be used to reduce aphid numbers in hot spots without harming the pupal stage of Aphidius.
Content Courtesy of Applied Bio-nomics Ltd.
