Temporal dynamics of woodpecker predation on emerald ash borer (Agrilus planipennis) in the northeastern U.S.A.

Abstract

1 Woodpeckers (Picidae) are important natural enemies attacking emerald ash borer (EAB) Agrilus planipennis Fairmaire in North America. There can be considerable variation in predation levels within and between sites, and among different times of year; therefore, understanding what causes these differences is necessary for effectively predicting EAB population dynamics. 2 We examined the temporal dynamics of woodpecker predation on EAB in Michigan and Maryland, as well as how they were affected by season, region, resource availability, tree size and crown condition. In Michigan, we quantified predation in association with EAB developmental stages on different trees over 2 years, whereas, in Maryland, we recorded woodpecker attacks on the same trees for 1 year. 3 Season was a significant predictor of woodpecker predation, with most occurring in winter when late-instar larvae were abundant. Predation also was affected by crown condition and tree size. Additionally, predation levels were similar throughout the year in a region where generations are considered to be less synchronized, representing a more consistent resource for woodpeckers. 4 The present study highlights the various factors affecting woodpecker predation over time. The results demonstrate the importance of multi-season studies of interactions between invasive species and native natural enemies when aiming to fully understand their dynamics.

Emerald ash borer biocontrol in ash saplings: The potential for early stage recovery of North American ash trees

“…Despite predictions that Fraxinus could be functionally extirpated from North American forests (Herms and McCullough 2014), research shows that tree mortality is moderated by several factors including ash species and genotype (Liu et al, 2003;Rebek et al, 2008;Koch et al, 2015); ash tree age, vigor, and stand density (Siegert et al, 2010;Kashian and Witter 2011;Mercader et al, 2011;Knight et al, 2013;Kashian 2016); pest population outbreak stages (Burr and McCullough 2014); climatic factors (Wu et al, 2007;Crosthwaite et al, 2011;DeSantis et al, 2013); and natural enemies (Liu et al, 2003(Liu et al, , 2007Lindell et al, 2008;Duan et al, 2010Duan et al, , 2012aDuan et al, , 2013aDuan et al, , 2015Bauer et al, 2015;Jennings et al, 2016bJennings et al, , 2016cMurphy 2017). Moreover, a recent five-year study of green ash (F. pennsylvanica) regeneration in the aftermath forests of southeast Michigan revealed seed production in small ash trees and basal ash sprouts in 2011 and subsequent seedling recruitment throughout the region (Kashian, 2016).…”

“…Since the start of biocontrol releases in 2007, field studies in different regions of North America have monitored emerald ash borer parasitoid populations for their establishment and prevalence (Duan et al, 2013a(Duan et al, , 2014(Duan et al, , 2015Abell et al, 2014;Bauer et al, 2015;Davidson and Rieske 2016;Parisio et al, 2017;Mapbiocontrol.org 2017). As the pest infestation continues to expand in ash stands in North America, predation of emerald ash borer larvae and pupae by woodpeckers and other bark-foraging birds, and larval parasitism by native parasitoids via new species associations, are regularly observed both in the invasion's epicenter in Michigan (Lindell et al 2008;Cappaert and McCullough, 2009;Duan et al, 2010Duan et al, , 2014Jennings et al, 2016c) and at its expanding edges (e.g., Colorado, Texas, New England, Ontario, and Quebec) (Kula et al, 2010;Duan et al, 2013b;Jennings et al, 2013Jennings et al, , 2016bJennings et al, , 2016cFlower et al, 2014;Roscoe et al, 2016).…”

Strategic removal of host trees in isolated, satellite infestations of emerald ash borer can reduce population growth

“…Following the early discovery of a satellite infestation of emerald ash borer in an urban area, tree removal may be a useful management tool to reduce populations of emerald ash borer as part of a broader, integrated pest management program. Larger diameter trees with pecking will likely contain the most larvae (McCullough & Siegert 2007;Lindell et al 2008;Jennings et al 2013Jennings et al , 2016.…”

“…As part of ongoing surveys from 2009-2013 following the discovery of emerald ash borer in Saint Paul, the MDA recorded diameter at breast height (DBH; approximately 1.4 m above ground) and presence/absence of foraging damage by woodpeckers (referred to henceforth as "pecked or pecking"/"unpecked", respectively) on every tree in the core infested area. In emerald ash borer infestations, pecking appears relatively early compared to other symptoms such as epicormic shoots and thinning of the crown (Baranchikov et al 2008;Lindell et al 2008; McCullough & Mercader 2012) and woodpecker predation is positively associated with densities of emerald ash borer (Lindell et al 2008;Jennings et al 2013Jennings et al , 2016. Thus, trees with pecking were targeted for removal.…”

Optimizing Use of Girdled Ash Trees for Management of Low-Density Emerald Ash Borer (Coleoptera: Buprestidae) Populations

“…Additional woodpecker predation on late instar emerald ash borer larvae occurred on the felled, intact trees (but not on the cut logs) between March and September, further reducing the number of adult beetles that could have emerged. Predation by woodpeckers commonly occurs in winter (Jennings et al 2016) and its potential impact on late instar larvae in girdled ash trees at sites with low emerald ash borer infestation levels may be maximized by felling girdled trees in late winter or early spring (N.W.S., unpublished data). In situations such as remote or difficult-to-access forested sites, negligible emerald ash borer emergence from felled or felled-and-sectioned trees would outweigh costs of removing those trees.…”