Not all sites fit the criteria for biological control. Once an EAB infestation is identified, several steps need to be completed to determine if biological control is viable:
- Perform a delimit survey of the infestation to identify the perimeter of where symptoms are visible.
- Gauge the intensity or pest pressure in the area based on severity of EAB symptoms throughout the identified visibly infested area. Low to moderate EAB densities are recommended for potential sites.
- Identify forested areas on public or private land within the visibly infested area where removal and/or treatment of infested ash trees will not be feasible. Size and composition of forest should be at least 40 acres and at a minimum include 20 percent ash of varying size class. Ideally, the site would be greater than 25 percent ash and connected to other woodlots.
Not all sites fit the criteria for biological control. Once an EAB infestation is identified, several steps need to be completed to determine if biological control is viable:
- Perform a delimit survey of the infestation to identify the perimeter of where symptoms are visible.
- Gauge the intensity or pest pressure in the area based on severity of EAB symptoms throughout the identified visibly infested area. Low to moderate EAB densities are recommended for potential sites.
- Identify forested areas on public or private land within the visibly infested area where removal and/or treatment of infested ash trees will not be feasible. Size and composition of forest should be at least 40 acres and at a minimum include 20 percent ash of varying size class. Ideally, the site would be greater than 25 percent ash and connected to other woodlots.
After a viable biological control site is identified, coordination by the MDA with local natural resource managers, property owners and the USDA EAB Parasitoid Rearing Facility are necessary. At each site one must obtain permission, guarantee access and ensure other management objectives won’t interfere with implementation. Special permits may be necessary depending on the ownership and designation of land. Long term site access is important for follow-up monitoring of ash health and documenting parasitoid establishment.
Oobius agrili (egg parasitoid)
Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae) wasps are so tiny that they are difficult to see (0.95 mm long). Adult females search ash bark crevices to find EAB eggs. A female will insert one of her eggs into an EAB egg. The wasps develop in the EAB eggs then emerge as an adult. There are at least two generations per year resulting in parasitism rates up to 60%. Oobius agrili overwinters as mature larvae in EAB eggs then adults emerge the following spring and summer. Each O. agrili female can parasitize up to 62 EAB eggs and can reproduce without males (parthenogenesis).
This detailed presentation shows how to look for Oobius agrili (PDF).
Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae) wasps are so tiny that they are difficult to see (0.95 mm long). Adult females search ash bark crevices to find EAB eggs. A female will insert one of her eggs into an EAB egg. The wasps develop in the EAB eggs then emerge as an adult. There are at least two generations per year resulting in parasitism rates up to 60%. Oobius agrili overwinters as mature larvae in EAB eggs then adults emerge the following spring and summer. Each O. agrili female can parasitize up to 62 EAB eggs and can reproduce without males (parthenogenesis).
This detailed presentation shows how to look for Oobius agrili (PDF).
Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae) wasps are so tiny that they are difficult to see (0.95 mm long). Adult females search ash bark crevices to find EAB eggs. A female will insert one of her eggs into an EAB egg. The wasps develop in the EAB eggs then emerge as an adult. There are at least two generations per year resulting in parasitism rates up to 60%. Oobius agrili overwinters as mature larvae in EAB eggs then adults emerge the following spring and summer. Each O. agrili female can parasitize up to 62 EAB eggs and can reproduce without males (parthenogenesis).
This detailed presentation shows how to look for Oobius agrili (PDF).
Tetrastichus planipennisi (larval parasitoid)
Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) are small parasitoids (1.6 to 4.1 mm long). Adult females locate EAB larvae under ash bark and insert eggs into EAB larva. Parasitized EAB larva remain active for approximately one week although the parasitoids develop within and eventually consume the EAB larvae. Tetrastichus planipennisi larvae pupate inside the EAB gallery and emerge approximately 15 days after pupation by chewing an exit hole through the bark. They overwinter as larvae within the host or host gallery. Approximately 4-172 progeny are produced per EAB larva. In China, T. planipennisi completes four or more generations per year and parasitism levels range from 0-65%.
Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) are small parasitoids (1.6 to 4.1 mm long). Adult females locate EAB larvae under ash bark and insert eggs into EAB larva. Parasitized EAB larva remain active for approximately one week although the parasitoids develop within and eventually consume the EAB larvae. Tetrastichus planipennisi larvae pupate inside the EAB gallery and emerge approximately 15 days after pupation by chewing an exit hole through the bark. They overwinter as larvae within the host or host gallery. Approximately 4-172 progeny are produced per EAB larva. In China, T. planipennisi completes four or more generations per year and parasitism levels range from 0-65%.
Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) are small parasitoids (1.6 to 4.1 mm long). Adult females locate EAB larvae under ash bark and insert eggs into EAB larva. Parasitized EAB larva remain active for approximately one week although the parasitoids develop within and eventually consume the EAB larvae. Tetrastichus planipennisi larvae pupate inside the EAB gallery and emerge approximately 15 days after pupation by chewing an exit hole through the bark. They overwinter as larvae within the host or host gallery. Approximately 4-172 progeny are produced per EAB larva. In China, T. planipennisi completes four or more generations per year and parasitism levels range from 0-65%.
