Monitoring field establishment of the emerald ash borer biocontrol agent Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae): Sampling methods, sample size, and phenology
- Download PDF (6.0 MB)
- This publication is available only online.
Monitoring Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae), an egg parasitoid being released for biological control of emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is challenging due to its small size and the cryptic placement of host eggs. We compared four O. agrili recovery methods: 1) rearing adults from bark (bark rearing); 2) sifting parasitized eggs from bark (bark sifting); 3) placing sentinel EAB eggs in screened envelopes on ash trees (sentinel eggs); and, 4) placing yellow pan traps on ash trees to capture adult parasitoids. In 2016, we sampled 40 trees within 0.25-ha-plots at each of 4 sites in Michigan with each recovery method. In 2017 and 2018, methods were applied to 10 trees within 0.25-ha-plots at each of 3 sites. Sentinel eggs were not included in 2018. Yellow pan traps and bark sifting recovered O. agrili in all sites and years, had higher percentages of O. agrili-positive trees, and required fewer trees sampled for > 95% probability of O. agrili recovery compared to bark rearing and sentinel eggs. When sampling only trees with fresh woodpecker-feeding holes, a sign of recent EAB attack, the probability of O. agrili recovery increased substantially for bark sifting and bark rearing, increased slightly for yellow pan traps, but decreased for sentinel eggs compared to sampling all trees. Peak recovery using yellow pan traps and sentinel eggs occurred between 400 and 1200 growing degree days (base 10 ◦C, January 1 start date), revealing when most O. agrili adults were active. The type of information each of these parasitoid-recovery methods provides and their relative efficiencies are discussed.
KeywordsSampling precision; Cost: benefit ratio; Invasive species; Survey methods; Insect trapping
Petrice, Toby R.; Bauer, Leah S.; Miller, Deborah L.; Stanovick, John S.; Poland, Therese M.; Ravlin, F. William. 2021. Monitoring field establishment of the emerald ash borer biocontrol agent Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae): Sampling methods, sample size, and phenology. Biological Control. 156(4): 104535. 13 p. https://doi.org/10.1016/j.biocontrol.2021.104535.