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Dive into the research topics where Gerald L. Nordin is active.

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Featured researches published by Gerald L. Nordin.


Oecologia | 1986

The role of host tree condition in attack of white oaks by the twolined chestnut borer, Agrilus bilineatus (Weber) (Coleoptera: Buprestidae)

James P. Dunn; Thomas W. Kimmerer; Gerald L. Nordin

SummaryThe twolined chestnut borer, Agrilus bilineatus (Weber) (Coleoptera: Buprestidae), attacks stressed oaks (Quercus spp.) and is associated with extensive mortality of trees in the eastern deciduous forests of North America. We examined host location by the insect and subsequent host mortality in experimentally stressed trees. A. bilineatus adults were able to rapidly and specifically locate stressed oak trees. Up to 160 beetles per week were captured on sticky band traps on the trunks of stressed trees, while beetles rarely landed on unstressed control trees. This suggests that adult borers have an acute perception of host tree “quality”, and that this perception is from a distance. One mechanism of host location may be detection of volatile compounds produced by stressed trees.The condition of the host tree appears to regulate both beetle attraction and successful colonization. Mortally wounded (xylem-girdled) trees attracted beetles only until the cambium died. Xylem-girdled trees were attacked early in the beetle flight season, but larvae did not survive to emerge as adults from these trees. In contrast, phloemgirdled trees continued to attract beetles throughout the flight period. Phloem-girdled trees which were heavily attacked by A. bilineatus died late in the season in which they were attacked. Lightly attacked trees survived until the following growing season, and were then heavily attacked and killed. In one stand, phloem-girdled trees were not attacked, healed over the girdling wounds and were still alive three years after girdling. These results indicate that oak trees are only attractive to A. bilineatus within a narrow range of physiological conditions following stress but prior to mortality. A. bilineatus appears to be a proximate agent of mortality in stressed oaks in eastern North America.


Oecologia | 1988

Nutritional physiology of the eastern spruce budworm, Choristoneura fumiferana, infected with Nosema fumiferanae, and interactions with dietary nitrogen

Leah S. Bauer; Gerald L. Nordin

SummaryFemale eastern spruce budworm larvae, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae), inoculated with a medium lethal spore dosage of the microsporidium Nosema fumiferanae (Thomson) exhibited significant reductions in consumptive index (CI), nitrogen consumptive index (NCI), relative growth rate (RGR), and gross (ECI) and net (ECD) production effeciencies when compared to microsporidian-free larvae. Diseased larvae also exhibited significant increases in approximate digestibility (AD), N utilization efficiency (NUE), and larval moisture content. Both healthy and diseased insects were reared on 2.5% N and 4.5% N diets. Those on the 2.5% N diet showed significant increases in CI, although NCI was still lower than NCI measured for larvae reared on 4.5% N. NUE was also higher on the 2.5% N diet. Diseased cohorts reared on 2.5% N diet had significantly greater mortality than those reared on 4.5% N diet. Pupal weight and development time of infected individuals did not respond to dietary N concentration. However, healthy insects achieved greater pupal weights in a shorter time on the 4.5% N diet than those on the 2.5% N diet. Mortality of healthy insects was unaffected by dietary N.


Bulletin of Mathematical Biology | 1982

An epizootic model of an insect-fungal pathogen system†

G. C. Brown; Gerald L. Nordin

A system of integro-differential equations is derived to describe epizootics of a fungal pathogen in an insect population. Because of piecewise continuous behavior under some parametric conditions, it is concluded that standard phase orbits can be misleading. Using a different analytic approach yields a simple system of finite difference equations. Both the continuous and discrete versions are compared to classical forms. The continuous version differs from a classical one in possessing a second derivative dependent on population density. The discrete version differs in maintaining positive, non-zero populations of both infectives and susceptibles in finite time.


Canadian Entomologist | 1986

Attraction of the twolined chestnut borer, Agrilus bilineatus (Weber) (Coleoptera: Buprestidae), and associated borers to volatiles of stressed white oak.

James P. Dunn; Thomas W. Kimmerer; Gerald L. Nordin


Environmental Entomology | 1989

Effect of Nosema fumiferanae (Microsporida) on Fecundity, Fertility, and Progeny Performance of Choristoneura fumiferana (Lepidoptera: Tortricidae)

Leah S. Bauer; Gerald L. Nordin


Environmental Entomology | 1995

Green Leaf Volatiles Inhibit Conidial Germination of the Entomopathogen Pandora neoaphidis (Entomopthorales: Entomophthoraceae)

G. C. Brown; G. L. Prochaska; David F. Hildebrand; Gerald L. Nordin; D. M. Jackson


Environmental Entomology | 1982

Microclimatic Humidity Influence on Conidial Discharge in Erynia sp. (Entomophthorales: Entomophthoraceae), an Entomopathogenic Fungus of the Alfalfa Weevil (Coleoptera: Curculionidae)

J. A. Millstein; G. C. Brown; Gerald L. Nordin


Environmental Entomology | 1983

Epizootic Phenology of Erynia Disease of the Alfalfa Weevil, Hypera postica (Gyllenhal) (Coleoptera: Curculionidae), in Central Kentucky

Gerald L. Nordin; G. C. Brown; J. A. Millstein


Environmental Entomology | 1983

Microclimatic Moisture and Conidial Production in Erynia sp. (Entomophthorales: Entomophthoraceae): In Vivo Production Rate and Duration Under Constant and Fluctuating Moisture Regimes

J. A. Millstein; G. C. Brown; Gerald L. Nordin


Canadian Entomologist | 1988

Pathogenicity Of Nosema fumiferanae (Thomson) (Microsporida) In Spruce Budworm, Choristoneura Fumiferana (Clemens), And Implications Of Diapause Conditions

Leah S. Bauer; Gerald L. Nordin

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G. C. Brown

University of Kentucky

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Leah S. Bauer

United States Forest Service

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B. C. Pass

University of Kentucky

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J. C. Parr

University of Kentucky

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