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16 pages, 1449 KiB

Open AccessArticle

Potential Impacts of Emerald Ash Borer Biocontrol on Ash Health and Recovery in Southern Michigan

by Daniel M. Kashian, Leah S. Bauer, Benjamin A. Spei, Jian J. Duan and Juli R. Gould

Forests 2018, 9(6), 296; https://doi.org/10.3390/f9060296 - 25 May 2018

Cited by 19 | Viewed by 4516

Emerald ash borer (EAB) is an invasive beetle that kills native North American ash species, threatening their persistence. A classical biological control program for EAB was initiated in 2007 with the release of three specialized EAB parasitoids. Monitoring changes in the health and regeneration of ash where EAB biocontrol agents have been released is critical for assessing the success of EAB biocontrol and predicting future changes to the ash component of North American forests. We sampled release and control plots across southern Michigan over a three-year period to measure ash health and recruitment to begin assessing the long-term impact of EAB biological control on ash populations. We noted a reduced mortality of larger trees between 2012 and 2015 in release plots compared to control plots and increases in ash diameter, but our results were otherwise inconsistent. Ash regeneration was generally higher in release plots compared to control plots but highly variable among sites, suggesting some protection of ash saplings from EAB by parasitoids. We conclude that EAB biocontrol is likely to have a positive effect on ash populations, but that the study duration was not long enough to definitively deduce the long-term success of the biocontrol program in this region. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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17 pages, 3546 KiB

Open AccessReview

Progress and Challenges of Protecting North American Ash Trees from the Emerald Ash Borer Using Biological Control

by Jian J. Duan, Leah S. Bauer, Roy G. Van Driesche and Juli R. Gould

Forests 2018, 9(3), 142; https://doi.org/10.3390/f9030142 - 15 Mar 2018

Cited by 83 | Viewed by 11205

Abstract

After emerald ash borer (EAB), Agrilus planipennis Fairmaire, was discovered in the United States, a classical biological control program was initiated against this destructive pest of ash trees (Fraxinus spp.). This biocontrol program began in 2007 after federal regulatory agencies and the state of Michigan approved release of three EAB parasitoid species from China: Tetrastichus planipennisi Yang (Eulophidae), Spathius agrili Yang (Braconidae), and Oobius agrili Zhang and Huang (Encyrtidae). A fourth EAB parasitoid, Spathius galinae Belokobylskij (Braconidae) from Russia, was approved for release in 2015. We review the rationale and ecological premises of the EAB biocontrol program, and then report on progress in North American ash recovery in southern Michigan, where the parasitoids were first released. We also identify challenges to conserving native Fraxinus using biocontrol in the aftermath of the EAB invasion, and provide suggestions for program improvements as EAB spreads throughout North America. We conclude that more work is needed to: (1) evaluate the establishment and impact of biocontrol agents in different climate zones; (2) determine the combined effect of EAB biocontrol and host plant resistance or tolerance on the regeneration of North American ash species; and (3) expand foreign exploration for EAB natural enemies throughout Asia. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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14 pages, 2124 KiB

Open AccessArticle

Buying Time: Preliminary Assessment of Biocontrol in the Recovery of Native Forest Vegetation in the Aftermath of the Invasive Emerald Ash Borer

by Elan Margulies, Leah Bauer and Inés Ibáñez

Forests 2017, 8(10), 369; https://doi.org/10.3390/f8100369 - 28 Sep 2017

Cited by 20 | Viewed by 7756

Abstract

Introduced forest pests have become one of the major threats to forests, and biological control is one of the few environmentally acceptable management practices. Assessing the impacts of a biocontrol program includes evaluating the establishment of biocontrol agents, the control of target pest, the impact on the affected organism, and the indirect impacts that the biocontrol agent may have on the whole community. We assessed the recovery of forest vegetation following the mortality of ash trees caused by the invasive emerald ash borer (EAB) pest in forest stands where biocontrol agents were released or not. We used a multilevel framework to evaluate potential indirect effects of the biocontrol agents on native forest seedlings. Our results showed a higher number of ash saplings where increasing numbers of the dominant EAB biocontrol agent were released, while the number of invasive and weedy saplings was negatively associated with the number of ash saplings, and the density of native seedlings was negatively associated with invasive and weedy saplings. The protection of ash saplings by the biocontrol agent may help native recruitment during forest transition by supporting the growth of native hardwood seedlings over invasive and weedy species. These results show that research on the efficacy of EAB biocontrol should include all ash size classes and the community dynamics of co-occurring species. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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