|Jennings, David - University Of Maryland|
|Bean, Dick - Maryland Department Of Agriculture|
|Gould, Juli - Animal And Plant Health Inspection Service (APHIS)|
|Rice, Kimberly - Maryland Department Of Agriculture|
|Shrewsbury, Paula - University Of Maryland Eastern Shore (UMES)|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/2016
Publication Date: 7/16/2016
Citation: Jennings, D.E., Duan, J.J., Bean, D., Gould, J., Rice, K.A., Shrewsbury, P.M. 2016. Monitoring the establishment and abundance of introduced parasitoids of emerald ash borer larvae in Maryland, U.S.A. Biological Control. 101:138–144.
Interpretive Summary: Emerald ash borer (EAB) is an invasive beetle now found throughout much of the United States including Maryland, where it was first detected in 2003. Since 2009, two species of small wasps that parasitize EAB larvae have been released as biological control agents in Maryland in an attempt to suppress populations of this beetle. Scientists from the University of Maryland, USDA ARS NEA, USDA APHIS and Maryland Department of Agriculture assessed the impact of these parasitic wasps by harvesting trees infested with EAB across the state of Maryland and examining EAB larvae present for signs of parasitism. While one of the wasp species was only found in very small numbers, the other species (Tetrastichus planipennisi) was much more successful at parasitizing EAB, and was found in increasing numbers each year after releases. Our results provide support for further releases of T. planipennisi in the Mid-Atlantic states as part of an integrated management strategy for mitigating EAB.
Technical Abstract: Classical biological control can be an important tool for managing invasive species such as emerald ash borer, Agrilus planipennis Fairmaire. Emerald ash borer is now widespread throughout the United States, and was first detected in Maryland in 2003. The biological control program to manage emerald ash borer in Maryland was initiated in 2009, and here we focus on efforts to monitor the establishment and abundance of two larval parasitoids (Spathius agrili Yang and Tetrastichus planipennisi Yang). A total of 56,677 S. agrili and 191,506 T. planipennisi were released at 26 and 32 sites, respectively, from 2009-2014. Monitoring efforts (i.e., debarking of trees, and harvesting trees to store in rearing barrels) were conducted at 47 sites from 2010-2015. We recovered 77 S. agrili from 16 emerald ash borer larvae at six sites, and 1,856 T. planipennisi from 110 emerald ash borer larvae at 19 sites. Percentage parasitism by T. planipennisi, and the mean percentage of trees containing T. planipennisi broods, were significantly positively associated with the number of years post-release of the parasitioids, reaching 11.6 % and 41.7% four years post-release, respectively. Additionally, parasitism by T. planipennisi was negatively associated with tree diameter at breast height. In summary, as in other northern states, T. planipennisi is establishing populations in Maryland, while comparatively few S. agrili were found. Moreover, T. planipennisi has rapidly been dispersing, and was detected at seven non-release control sites. These findings should be useful in guiding future emerald ash borer biological control efforts in the Mid-Atlantic region of the United States.