Parasitism of Spruce Budworm by <i>Glypta</i> and <i>Apanteles</i> at Different Crown Heights in Montana

Dodge, Harold R.

doi:10.4039/ent93222-3

Cited by 11 publications

(10 citation statements)

References 4 publications

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“…Herbivorous insects are commonly thought to optimize their foraging in order to maximize nutrition and minimize attack by natural enemies (e.g., Carroll & Quiring, 1994). However, there are many exceptions to this rule; for example, spruce budworm larvae prefer to feed on the nutritious foliage in the upper canopy of host trees, which is also where they experience the highest parasitism rates and pathogen infection (Dodge, 1961; Régnière, Lysyk & Auger, 1989). Caterpillars in our study were the only group whose density was highest above the understory, although the overall low numbers of caterpillars observed make comparisons difficult.…”

Section: Discussionmentioning

confidence: 99%

Vertical heterogeneity in predation pressure in a temperate forest canopy

Aikens

Timms

Buddle

2013

PeerJ

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The forest canopy offers a vertical gradient across which variation in predation pressure implies variation in refuge quality for arthropods. Direct and indirect experimental approaches were combined to assess whether canopy strata differ in ability to offer refuge to various arthropod groups. Vertical heterogeneity in impact of avian predators was quantified using exclosure cages in the understory, lower, mid, and upper canopy of a north-temperate deciduous forest near Montreal, Quebec. Bait trials were completed in the same strata to investigate the effects of invertebrate predators. Exclusion of birds yielded higher arthropod densities across all strata, although treatment effects were small for some taxa. Observed gradients in predation pressure were similar for both birds and invertebrate predators; the highest predation pressure was observed in the understory and decreased with height. Our findings support a view of the forest canopy that is heterogeneous with respect to arthropod refuge from natural enemies.

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Section: Discussionmentioning

confidence: 99%

Vertical heterogeneity in predation pressure in a temperate forest canopy

Aikens

Timms

Buddle

2013

PeerJ

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“…Similar trends of parasitism by A. fumiferanae bave been sbown in sbort-term studies carried out previously (e.g.. Dodge 1961). No detailed studies have been carried out to determine wby A. fumiferanae appear to preferentially attack larvae in the upper crown; however, it has been speculated tbat the higher relative density of larvae in the upper crown may provide a smaller search area and fewer deep crevices, epiphytic plants, and lichen for larvae to conceal themselves iti (Dodge 1961). Parasitism of L2 by G. fumiferanae, a competitor of A. fumiferanae, was weakly biased toward the upper crown in only 1 of the 4 yr of our study (Eig.…”

Section: Discussionmentioning

confidence: 71%

Intratree Variation in the Seasonal Distribution and Mortality of Spruce Budworm (Lepidoptera: Tortricidae) from the Peak to Collapse of an Outbreak

Eveleigh

Johns

2014

Annals of the Entomological Society of America

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A 5-yr field study was carried out to assess intratree variations in the distribution, abundance, and mortality of immature spruce budworm (Choristoneura fumiferana Clemens) (Lepidoptera: Tortricidae) from the peak to collapse of an outbreak. In most years, the highest density of overwintering second-instar (L2) larvae (per square meter of foliage) was located in the lower crown, whereas all subsequent stages (third-to sixth-instar larvae, pupae, and eggs) were at relatively higher densities in the upper crown. In contrast, overall abundance (per branch) throughout the season tended to be highest in the mid-upper to mid-lower crown. Mortality associated with 16 different parasitoid species varied significantly among years but varied among crown levels for only a few species. In particular, Apanteles fumiferanae (Viereck), Glypta fumiferanae (Viereck), Smidtia fumiferanae (Tothill), and Trichogramma minutum (Riley) all caused higher mortality in the upper crown of trees. Although infection associated with Nosema fumiferanae (Thomson) and mortality associated with fungal and viral pathogens often varied among crown levels, there was no clear or consistent trend from year to year. In general, trends in spruce budworm density and mortality within the crown were similar throughout all years of our study, despite significant variations in herbivore density, foliage availability, and parasitoid and pathogen impact. Our study indicates that intratree patterns of spruce budworm distribution and mortahty are likely to remain consistent during an outbreak and further emphasizes the importance of intratree heterogeneity in shaping interactions within plant-herbivore-parasitoid communities.

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“…The stress of scarce budworm resources should be less severe upon T. interruptum, as it can utilize those additional hosts. Glypta fumiferanae is competitively inferior to A. fumiferanae within a budworm host (Dodge 1961) and is not as proficient at attacking free-crawling larvae (Lewis 1960;Rappaport and Page 1985). Competitive inferiority and dependence upon larvae already within hibernaculae, dispersed throughout the forest, could explain why G .…”

Section: Methodsmentioning

confidence: 99%

PARASITOIDS OF ENDEMIC AND EPIDEMIC POPULATIONS OF CHORISTONEURA OCCIDENTALIS FREEMAN AND CHORISTONEURA RETINIANA (WALSINGHAM) (LEPIDOPTERA: TORTRICIDAE) IN SOUTHERN OREGON

1991

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Parasitoid species attacking sparse, endemic populations of Choristoneura occidentalis Freeman and C. retiniana (Walsingham) are reported from 2 years of host collections at seven sites across southern Oregon. Results are compared with rearings from epidemic populations either from the same region or the same plot. Collections were designed to allow quantitative estimation of host density. Most of the parasitoid species present during epidemics across North America were recovered from the endemic and epidemic populations studied. The major difference is that at endemic host densities Glypta fumiferanae (Viereck) (Ichneumonidae) is rare to absent, whereas ichneumonids of the tribe Campoplegini, especially Tranosema (= Diadegma) interruptum (Ashmead), are common. This is the reverse of the situation at epidemic densities and consistent with results reported from eastern North America. It is suggested that the observed shift in the parasite complex with budworm density has the potential for predicting population trends.

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Parasitism of Spruce Budworm by Glypta and Apanteles at Different Crown Heights in Montana

Cited by 11 publications

References 4 publications

Vertical heterogeneity in predation pressure in a temperate forest canopy

Vertical heterogeneity in predation pressure in a temperate forest canopy

Intratree Variation in the Seasonal Distribution and Mortality of Spruce Budworm (Lepidoptera: Tortricidae) from the Peak to Collapse of an Outbreak

PARASITOIDS OF ENDEMIC AND EPIDEMIC POPULATIONS OF CHORISTONEURA OCCIDENTALIS FREEMAN AND CHORISTONEURA RETINIANA (WALSINGHAM) (LEPIDOPTERA: TORTRICIDAE) IN SOUTHERN OREGON

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