Evaluation of tree mortality and parasitoid recoveries on the contiguous western invasion front of emerald ash borer

Abstract

1 A recent invader to North America, emerald ash borer Agrilus planipennis Fairmaire (Buprestidae), is expanding its western range into new habitats. We examined how site factors affect the emergence and damage caused by this beetle on the western edge of its contiguous population in eastern Wisconsin, U.S.A. We characterized forest structure and quantified signs and symptoms of A. planipennis from 2010 to 2013. 2 We evaluated the potential for establishment of three host-specific parasitic Hymenoptera, released as biological control agents of A. planipennis. During June to September 2011, we conducted releases of 1500 Oobius agrili Zhang and Huang (Encyrtidae), 1900 Spathius agrili Yang (Braconidae) and 2700 Tetrastichus planipennisi Yang (Eulophidae) at the same location. 3 Signs and symptoms of A. planipennis increased in abundance during the present study. Emergence of A. planipennis was greater in larger diameter trees and in subplots with more ash trees. More epicormic shoots were on the upper halves of trees in subplots with a higher percentage of ash. Fraxinus nigra exhibited a higher incidence of ruptured bark than Fraxinus pennsylvanica. 4 In January 2013, we felled four infested ash trees and censused insect emergence from the entire trees. We recovered 441 A. planipennis, 41 T. planipennisi and no other released parasitoids. 5 These results suggest that, of these three parasitoids, T. planipennisi has the highest likelihood of contributing to biological control in Wisconsin, although ash mortality will proceed rapidly and likely supersede the effects of the parasitoids. The best opportunity for introduced parasitoids to benefit Wisconsin may arise in post-outbreak, recovering forests.

Monitoring the establishment and abundance of introduced parasitoids of emerald ash borer larvae in Maryland, U.S.A.

“…As has been observed elsewhere in northern states (Duan et al, 2012a(Duan et al, , 2014(Duan et al, , 2015aJohnson et al, in press), we found little evidence that S. agrili was successfully establishing or dispersing even though this species can parasitize up to 50% of EAB larvae in China (Liu et al, 2003), and some experimental work had suggested that the climate in Maryland might facilitate greater parasitism by this species compared with Michigan (Ulyshen et al, 2011). Given that just three EAB larvae parasitized by S. agrili were found at sites two years post-release, it is perhaps more likely that this parasitism was the result of dispersing from a recent release at a nearby site rather than establishment.…”

Effects of the emerald ash borer invasion on the community composition of arthropods associated with ash tree boles in Maryland, U.S.A.

“…Although only two of the seven parasitoids identified to species are EAB specialists introduced for biological control, four of the other species are known to attack EAB (Marsh & Strazanac, ; Kula et al , ; Duan et al , , ). Thus, the notable increases in relative abundance of Braconidae, Eupelmidae and Ichnuemonidae by 2014 could suggest that some native parasitoids might be responding numerically to EAB populations, similar to trends in other states (Duan et al , , , ; Hooie et al , ; Johnson et al , ).…”

Impact of braconid wasps on larval performance of longhorned borer Coptocercus rubripes Boisduval (Coleoptera: Cerambycidae) in Eucalyptus forest of southwestern Australia

“…This inability to regulate high larval densities was also exhibited by the same braconid wasps in a previous study attacking P. semipunctata in E. globulus Labillardière and E. obliqua L'Héritier logs in eastern Australia (Hanks et al 2001). This response appears to depend on factors altering wasp effectiveness in finding larval hosts which may include use of volatiles to locate borer infested hosts (Johnson et al 2016), acoustic cues and audible mechanisms suggested to be used by wasps to find P. semipunctata larvae feeding on the phloem/sapwood (Joyce et al 2011), surface vibrations from borer larvae feeding (Godfray 1994) as was suggested to be used by these braconid wasps when attacking P. semipunctata (Hanks et al 2001), and intensive searching by other braconid wasps (Richerson & Borden 1972). Also, the increased choice of borer infested hosts, combined with the habit of these wasps to land on logs arbitrarily, rather than to remain in one place (Driessen & Bernstein 1999), may have meant that the braconid wasps were likely dispersing throughout the clearfell site and had moved away from host logs with high neonate densities, rather than increasing their chances of finding more individuals among a few logs.…”

“…This response appears to depend on factors altering wasp effectiveness in finding larval hosts which may include use of volatiles to locate borer infested hosts (Johnson et al . 2016), acoustic cues and audible mechanisms suggested to be used by wasps to find P. semipunctata larvae feeding on the phloem/sapwood (Joyce et al . 2011), surface vibrations from borer larvae feeding (Godfray 1994) as was suggested to be used by these braconid wasps when attacking P. semipunctata (Hanks et al .…”