Impact of<i>Entomophaga maimaiga</i>(Entomophthorales: Entomophthoraceae) on Outbreak Gypsy Moth Populations (Lepidoptera: Erebidae): The Role of Weather

Reilly, James R.; Hajek, Ann E.; Liebhold, Andrew M.; Plymale, Ruth

doi:10.1603/en13194

Cited by 38 publications

(28 citation statements)

References 22 publications

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“…This positive relation to density is what we would expect for LdMNPV [55], and has also been found for E. maimaiga in some studies [27,56], but is not always the case (e.g. [35]), probably because environmental conditions also impact E. maimaiga infection [57] and can restrict density-related responses.…”

Section: (B) Associations With Host Densitysupporting

confidence: 85%

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Fatal diseases and parasitoids: from competition to facilitation in a shared host

Hajek

Nouhuys

2016

Proc. R. Soc. B.

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Diverse parasite taxa share hosts both at the population level and within individual hosts, and their interactions, ranging from competitive exclusion to facilitation, can drive community structure and dynamics. Emergent pathogens have the potential to greatly alter community interactions. We found that an emergent fungal entomopathogen dominated pre-existing lethal parasites in populations of the forest defoliating gypsy moth, Lymantria dispar. The parasite community was composed of the fungus and four parasitoid species that only develop successfully after they kill the host, and a virus that produces viable propagules before the host has died. A low-density site was sampled over 17 years and compared with 66 sites across a range of host densities, including outbreaks. The emergent fungal pathogen and competing parasitoids rarely co-infected host individuals because each taxa must kill its host. The virus was not present at low host densities, but successfully co-infected with all other parasite species. In fact, there was facilitation between the virus and one parasitoid species hosting a polydnavirus. This newly formed parasite community, altered by an emergent pathogen, is shaped both by parasite response to host density and relative abilities of parasites to co-inhabit the same host individuals.

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Section: (B) Associations With Host Densitysupporting

confidence: 85%

“…Historically, before the fungus arrived in the USA, the virus caused epizootics ending host outbreaks [57] and the community of introduced parasitoids caused higher mortality than we found [46,47]. The fungal pathogen now outcompetes parasitoids within gypsy moth caterpillars at a range of host densities.…”

Section: Resultsmentioning

confidence: 60%

Fatal diseases and parasitoids: from competition to facilitation in a shared host

Hajek

Nouhuys

2016

Proc. R. Soc. B.

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“…This is the second study to show that weather conditions before gypsy moth egg hatch are associated with subsequent E. maimaiga infection levels (Hajek and Tobin 2011). Other studies have also demonstrated repeatedly that when E. maimaiga is active (the fungus is inactive 10 months of the year), infection prevalence is positively related to moisture levels (Hajek 1999;Reilly et al 2014). In contrast, LdNPV infections were positively associated with precipitation in April and June but not May.…”

Section: Discussionmentioning

confidence: 67%

“…Entomophaga maimaiga and LdNPV can co-infect hosts (Malakar et al 1999) and are frequently both present in higher density L. dispar populations (AEH, unpublished data; Reilly et al 2014). …”

Section: Study Systemmentioning

confidence: 99%

Replacement of a dominant viral pathogen by a fungal pathogen does not alter the collapse of a regional forest insect outbreak

2014

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Natural enemies and environmental factors likely both influence the population cycles of many forest-defoliating insect species. Previous work suggests precipitation influences the spatiotemporal patterns of gypsy moth outbreaks in North America, and it has been hypothesized that precipitation could act indirectly through effects on pathogens. We investigated the potential role of climatic and environmental factors in driving pathogen epizootics and parasitism at 57 sites over an area of ≈72,300 km(2) in four US mid-Atlantic states during the final year (2009) of a gypsy moth outbreak. Prior work has largely reported that the Lymantria dispar nucleopolyhedrovirus (LdNPV) was the principal mortality agent responsible for regional collapses of gypsy moth outbreaks. However, in the gypsy moth outbreak-prone US mid-Atlantic region, the fungal pathogen Entomophaga maimaiga has replaced the virus as the dominant source of mortality in dense host populations. The severity of the gypsy moth population crash, measured as the decline in egg mass densities from 2009 to 2010, tended to increase with the prevalence of E. maimaiga and larval parasitoids, but not LdNPV. A significantly negative spatial association was detected between rates of fungal mortality and parasitism, potentially indicating displacement of parasitoids by E. maimaiga. Fungal, viral, and parasitoid mortality agents differed in their associations with local abiotic and biotic conditions, but precipitation significantly influenced both fungal and viral prevalence. This study provides the first spatially robust evidence of the dominance of E. maimaiga during the collapse of a gypsy moth outbreak and highlights the important role played by microclimatic conditions.

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“…Unlike bark beetle attacks, which typically kill trees quickly, severe defoliation over multiple years is usually required to kill trees, particularly in deciduous species (Van Asch & Visser, ). Natural enemies, which generally have a larger limiting effect on defoliator population dynamics than on bark beetles, are affected by temperature (especially predators and parasites) and precipitation (especially entomopathogens) (Jamieson et al ., ; Reilly et al ., ).…”

Section: Drought and Insect Mortality Pathwaysmentioning

confidence: 97%

Tree mortality from drought, insects, and their interactions in a changing climate

et al. 2015

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SummaryClimate change is expected to drive increased tree mortality through drought, heat stress, and insect attacks, with manifold impacts on forest ecosystems. Yet, climate-induced tree mortality and biotic disturbance agents are largely absent from process-based ecosystem models. Using data sets from the western USA and associated studies, we present a framework for determining the relative contribution of drought stress, insect attack, and their interactions, which is critical for modeling mortality in future climates. We outline a simple approach that identifies the mechanisms associated with two guilds of insects -bark beetles and defoliators -which are responsible for substantial tree mortality. We then discuss cross-biome patterns of insect-driven tree mortality and draw upon available evidence contrasting the prevalence of insect outbreaks in temperate and tropical regions. We conclude with an overview of tools and promising avenues to address major challenges. Ultimately, a multitrophic approach that captures tree physiology, insect populations, and tree-insect interactions will better inform projections of forest ecosystem responses to climate change.

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Impact ofEntomophaga maimaiga(Entomophthorales: Entomophthoraceae) on Outbreak Gypsy Moth Populations (Lepidoptera: Erebidae): The Role of Weather

Cited by 38 publications

References 22 publications

Fatal diseases and parasitoids: from competition to facilitation in a shared host

Fatal diseases and parasitoids: from competition to facilitation in a shared host

Replacement of a dominant viral pathogen by a fungal pathogen does not alter the collapse of a regional forest insect outbreak

Tree mortality from drought, insects, and their interactions in a changing climate

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