Spring Larval Dispersal of the Western Spruce Budworm (Lepidoptera: Tortricidae) in North-Central Washington
1

Beckwith, Roy C.; Burnell, Donald G.

doi:10.1093/ee/11.4.828

Cited by 18 publications

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“…This positive effect of partial clearing on damage has been noted before (Fauss and Pierce 1969;Carlson et al 1985Carlson et al , 1988, but the reasons were unclear. Earlier measurements suggested that losses of dispersing early-stage larvae in the spring are greater in thinned than in fully stocked stands (Kemp and Simmons 1979;Beckwith and Burnell 1982; but see Carlson et al 1985). However, no direct link between these dispersal losses, survival trends, and resulting densities of feeding budworm was made.…”

Section: Discussionmentioning

confidence: 97%

“…For this purpose, ten 45 cm square sticky traps were placed in each plot prior to spring emergence of budworms and checked weekly until the few larvae trapped were fourth instars. Budworms captured on these sticky traps were considered lost to the population, as they would unlikely regain the host tree (Beckwith and Burnell 1982). Budworm losses, measured as the number of insects lost per hectare, were converted to the number of insects lost per kilogram of foliage, l 2 , by dividing the observed number of insects lost per hectare by the estimate of foliage mass per hectare for each site (Table 1).…”

Section: Sampling Western Spruce Budwormmentioning

confidence: 99%

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Balancing risks of disturbance from mountain pine beetle and western spruce budworm

et al. 2009

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The effect of removing lodgepole pine (Pinus contorta Dougl. ex Loud.) and retaining Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) to reduce the risk of disturbance from mountain pine beetle (Dendroctonus ponderosae Hopk.) in mixed conifer stands in southern British Columbia, Canada, on population processes influencing outbreaks of western spruce budworm (Choristoneura occidentalis Free.) was evaluated in 10 paired (open vs. closed) field plots. Overall feeding damage to Douglas-fir was significantly, but only slightly, lower in open stands compared with closed stands. Although open plots tended to recruit more budworms, the losses resulting from the dispersal of spring-emerging budworms in search of feeding sites were significantly greater in open plots. The forest management benefits of these early season losses were mitigated, however, by more mortality of budworms from natural enemies, particularly diseases, in the closed plots during the budworm feeding period. These results are discussed in terms of compensating population processes and balancing objectives in forest pest management. In this case, selective harvesting of lodgepole pine as a mitigation strategy for the mountain pine beetle conserved the midterm timber supply potential represented by associated Douglas-fir even in the presence of an outbreak of the western spruce budworm.Résumé : Dans les peuplements mélangés de conifères du sud de la Colombie-Britannique, au Canada, on élimine le pin tordu (Pinus contorta Dougl. ex Loud.) en conservant le douglas de Menzies (Pseudotsuga menziesii (Mirb.) Franco) pour réduire les risques de perturbation par le dendroctone du pin ponderosa (Dendroctonus ponderosae Hopk.). L'effet de cette pratique sur les processus démographiques qui influencent les épidémies de tordeuse occidentale de l'épinette (Choristoneura occidentalis Free.) a été évalué dans 10 paires (peuplements ouverts vs peuplements fermés) de parcelles sur le terrain. Globalement, les dommages subis par le douglas de Menzies à cause du broutement étaient, quoique légèrement, significativement plus faibles dans les peuplements ouverts que dans les peuplements fermés. Bien que les peuplements ouverts aient eu tendance à recruter plus de tordeuses, les pertes dues à la dispersion des tordeuses qui émergent au printemps à la recherche d'endroits pour se nourrir étaient plus élevées dans les peuplements ouverts. À la suite de ces pertes en début de saison, les bénéfices de l'aménagement forestier ont cependant été atténués par une plus forte mortalité des tordeuses causée par ses ennemis naturels, particulièrement les maladies, dans les peuplements fermés pendant la période de broutement de la tordeuse. La discussion porte sur la compensation des processus démographiques et l'équilibre entre les objectifs en lien avec le contrôle des ravageurs forestiers. Dans ce cas, la stratégie qui préconise la récolte sélective du pin tordu pour atténuer l'impact du dendroctone du pin ponderosa a permis de maintenir le potentiel d'approvisionnement en bois à mi...

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Section: Discussionmentioning

confidence: 97%

Section: Sampling Western Spruce Budwormmentioning

confidence: 99%

Balancing risks of disturbance from mountain pine beetle and western spruce budworm

et al. 2009

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“…Wellington (1950a) showed that the crawling rate of budworms increased with the rate of evaporation within a broad range of temperatures and so dry periods tend to increase the risk of dispersal by increasing the propensity to disperse. Wet weather actually conserves budworms by decreasing dispersal rates ( Beckwith & Burnell, 1982 ). There are interactions between temperature and humidity that affect the microclimate of needle mines ( Wellington, 1950b ) but we did not measure such effects.…”

Section: Sitementioning

confidence: 99%

Risk of dispersal in western spruce budworm

Nealis

Régnière

2009

Agri and Forest Entomology

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1 Western spruce budworm Choristoneura occidentalis Free. larvae emerge in the spring before buds have expanded and spend a variable period of time foraging on branches and mining needles. 2 Losses of dispersing budworms during this needle-mining period are related directly to the severity of defoliation in previous years and inversely related to foliage biomass in the study plot and to temperature and rainfall during the needle-mining period. 3 Losses can be interpreted in terms of risk of dispersal, which is the product of the propensity of early-stage budworms to disperse in search of resources and the consequences of this behaviour for survival under variable ecological conditions. 4 A comparison of the species-specific nature of risk of dispersal in three coniferfeeding budworm systems of North America may elucidate the common nature but variable features of their respective population dynamics.

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“…Budflush on the other hand is determined by both air and ground temperature (LAVEN-DER et al 1973). BECKWITH and BURNELL (1982) found that in two of four years in north central Washington climatic conditions were such (warm air temperatures over dee snow packs keeping ground temperatures low) that larvae were forced to either feed on older foliage or seek a new host, either of which results in high 2nd instar mortality. In the mesic environments occupied by var.…”

Section: Discussionmentioning

confidence: 99%

Genetic and environmental influences in host resistance to herbivory: Douglas‐fir and the Western Spruce Budworm¹

Perry

Pitman

1983

Zeitschrift für Angewandte Entomologie

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Western spruce budworm rarely reach epidemic status west of the Cascade Mountain's Crest in Oregon while in the eastern portion of the state outbreaks occur periodically. Foliage from westside Douglas‐fir var. menziesii seedlings grown in a common garden caused no significant larval mortality but some pupal mortality was noted when bioassayed with a laboratory colony of spruce budworm. Conversely, foliage from seedlings of the Douglas‐fir var. glauca grown in the same garden caused a wide range of larval mortality ranging from nearly 100% mortality to no significant killing. Pupal mortality was significantly higher than control (artificial diet with var. menziesii foliage supplement) and peaked at 40%. Two year old foliage taken from mature trees of var. glauca gave highly variable bioassay results. In the 1981 foliage collections trees varied significantly in the larval mortality they produced, and in the 1982 collections there was significant variation in both larval and pupal mortality. There was also variation in time. In one stand 9 of 10 trees produced higher larval mortality, and lower pupal mortality, in 1982 than in 1981. Control mortality remained relatively constant between the two years. This change in foliage defenses was coincident with the very early stages of a budworm outbreak in the vicinity of the stand, though we detected no budworm in our sampled trees. In the continental environments occupied by var. glauca, environmental stress such as drought may alter the trees ability to produce allelochemics, and thus play a key role in regulating eastside spruce budworm populations. The apparent lack of constitutive defensive chemicals in the foliage of var. menziesii populations suggests that inducible defenses may play a role. Our results did not show the latter to be important, however, this may be due to our experimental technique. Alternatively, in the mesic, species‐rich, ecosystems occupied by var. menziesii, predators and parasites may act to maintain budworm populations at relatively low levels. Zusammenfassung Genetische und umweltbedingte Einflüsse auf die Resistenz der Wirtspflanze gegen Blatt‐ und Nadelfraß: Douglasie und Triebwickler Der Triebwickler Choristoneura occidentalis tritt in Oregon westlich vom Kamm der Kaskaden fast nie epidemisch auf, während östlich davon häufig Massenvermehrungen vorkommen. Nadel‐material von Sämlingen der im Westen vorkommen Douglasie var. menziesii verursachte im Laborversuch bei Larven des Triebwicklers kaum, bei Puppen nur wenig Mortalität. Dagegen führte Nadelmaterial von Sämlingen der Varietät glauca (die im gleichen Garten aufgewachsen waren), zu unterschiedlichen Mortalitätsraten zwischen 0 und 100%. Die Puppenmortalität war signifikant höher als in unbehandelten Vergleichszuchten (Kunstfutter mit Zusatz von menziesii‐Nadeln) und hatte ihr Maximum bei 40%. Zwei Jahre alte Nadeln von Altbäumen der var. glauca führten zu sehr variablen Ergebnissen. Verschiedene Nadelherkünfte des Jahres 1981 unterschieden sich signifikant hinsichtlich der von...

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Spring Larval Dispersal of the Western Spruce Budworm (Lepidoptera: Tortricidae) in North-Central Washington 1

Cited by 18 publications

References 0 publications

Balancing risks of disturbance from mountain pine beetle and western spruce budworm

Balancing risks of disturbance from mountain pine beetle and western spruce budworm

Risk of dispersal in western spruce budworm

Genetic and environmental influences in host resistance to herbivory: Douglas‐fir and the Western Spruce Budworm¹

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Spring Larval Dispersal of the Western Spruce Budworm (Lepidoptera: Tortricidae) in North-Central Washington 1

Cited by 18 publications

References 0 publications

Balancing risks of disturbance from mountain pine beetle and western spruce budworm

Balancing risks of disturbance from mountain pine beetle and western spruce budworm

Risk of dispersal in western spruce budworm

Genetic and environmental influences in host resistance to herbivory: Douglas‐fir and the Western Spruce Budworm1

Contact Info

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Genetic and environmental influences in host resistance to herbivory: Douglas‐fir and the Western Spruce Budworm¹