MORTALITY OF LARVAE IN STOCKED COHORTS OF THE DOUGLAS-FIR TUSSOCK MOTH, ORGYIA PSEUDOTSUGATA (LEPIDOPTERA: LYMANTRIIDAE)

1983 ◽  
Vol 115 (9) ◽  
pp. 1119-1127 ◽  
Author(s):  
R. R. Mason ◽  
T. R. Torgersen
Keyword(s):  
Douglas Fir ◽  
Total Loss ◽  
Abies Concolor ◽  
Bird Predation ◽  
Tussock Moth ◽  
Orgyia Pseudotsugata ◽  
White Fir ◽  
Arthropod Predation ◽  
Early Larvae

AbstractCohorts of instar I larvae of the Douglas-fir tussock moth, Orgyia pseudotsugata, were stocked on branches of white fir, Abies concolor. Branches were either exposed naturally over drop-trays or protected with cages of nylon netting. Only 8.7% of the larvae in exposed cohorts survived to pupate, compared with 68.0% survival in caged cohorts where dispersal and predation were prevented. Losses from the exposed cohorts were caused mostly by arthropod predation, disappearance, and non-replaced dispersal. Disappearance of early larvae was attributed primarily to predation by spiders and insects while disappearance of late larvae was suspected to be due mostly to bird predation. In an analysis of k-values, actual or suspected predation accounted for 47.2% and dispersal 40.5% of the total loss.

WITHIN AND BETWEEN TREE VARIATION OF LIVE AND PARASITIZED DOUGLAS-FIR TUSSOCK MOTH, ORYGIA PSEUDOTSUGATA (LEPIDOPTERA: LYMANTRIIDAE), COCOONS ON WHITE FIR IN CENTRAL CALIFORNIA AND ITS IMPLICATIONS FOR SAMPLING

1980 ◽  
Vol 112 (3) ◽  
pp. 231-238 ◽  
Author(s):  
Robert F. Luck ◽  
Donald L. Dahlsten
Keyword(s):  
Sierra Nevada ◽  
Douglas Fir ◽  
The Other ◽  
Central California ◽  
Tree Distribution ◽  
Tussock Moth ◽  
Orgyia Pseudotsugata ◽  
White Fir ◽  
Sierra Nevada Mountains ◽  
Total Parasitism

AbstractThe distribution of Douglas-fir tussock moth, Orgyia pseudotsugata (McD.), cocoons was studied within and between the crowns of white fir, Abies concolor ((Gord. and Glend.) Lindl.), at six locations in the central Sierra Nevada Mountains of California. The within tree, between tree, and between plot distribution of cocoons in the crown, categorized by sex, mortality (including parasitization), and stage (larva or pupa) were analyzed. Only cocoons containing female pupae varied in their distribution within the tree and they were concentrated in the bottom third of the live crown but their densities at any one level bore little relation to those in the other levels within the crown. Cocoon density varied significantly between plots and between trees within plots. Total parasitism did not vary significantly between plots. The variable within tree distribution of cocoons containing female pupae and their increased percentage parasitism relative to those containing male pupae, suggested that the live crown should be stratified. A sample unit consisting of two branches selected from the midpoint of each of the three crown levels (total: 6 branches) sampled approximately 5% of the live crown of white fir. The relation between the number of sample trees and mean cocoon density at three levels of precision is provided.

DISTRIBUTION AND PARASITIZATION OF COCOONS OF THE DOUGLAS-FIR TUSSOCK MOTH, HEMEROCAMPA PSEUDOTSUGATA (LEPIDOPTERA: LYMANTRIIDAE), IN AN ISOLATED INFESTATION

1970 ◽  
Vol 102 (2) ◽  
pp. 175-181 ◽  
Author(s):  
Donald L. Dahlsten ◽  
E. Alan Cameron ◽  
William A. Copper
Keyword(s):  
Sex Ratio ◽  
Natural Enemies ◽  
Douglas Fir ◽  
Abies Concolor ◽  
Tussock Moth ◽  
White Fir

AbstractDouglas-fir tussock moth cocoons were collected and their distribution recorded by crown level on white fir, Abies concolor, in northeastern California. Nine trees were sampled in two defoliation classes, light (20–30% defoliated) and moderate to heavy (50–80% defoliated). Cocoons were more abundant in the lower crown levels as defoliation became greater. The proportion of female cocoons increased toward the lower levels of the crown. An overall sex ratio of 1.2♂:1.0♀ was recorded. Significantly more male cocoons were parasitized than female. A list of the natural enemies of the tussock moth from the study area is given.

PARASITOIDS AND PREDATORS OF THE DOUGLAS-FIR TUSSOCK MOTH, ORGYIA PSEUDOTSUGATA (LEPIDOPTERA: LYMANTRIDAE), IN LOW TO MODERATE POPULATIONS IN CENTRAL CALIFORNIA

1977 ◽  
Vol 109 (5) ◽  
pp. 727-746 ◽  
Author(s):  
D. L. Dahlsten ◽  
R. F. Luck ◽  
E. I. Schlinger ◽  
J. M. Wenz ◽  
W. A. Copper
Keyword(s):  
Sierra Nevada ◽  
Egg Parasitoid ◽  
Host Population ◽  
Douglas Fir ◽  
Egg Mass ◽  
Moth Population ◽  
Tussock Moth ◽  
Orgyia Pseudotsugata ◽  
White Fir ◽  
Pupal Parasitoids

AbstractDouglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), populations were studied on white fir at four areas in central Sierra Nevada mountains of California during 1971–73. Life tables were constructed for four populations in El Dorado County. The number of eggs per egg mass decreased and the percentage eggs parasitized doubled with declining moth populations. Hymenopterous parasitoids were collected from all immature stages of the moth: one egg parasitoid, Telenomus californicus Ashmead, six species of larval parasitoids, principally, Hyposoter sp., and 13 species of larval–pupal parasitoids. Tachinids were predominant and accounted for 73% of the parasitoidism of the cocoons in 1971. The apparent mortality of female pupae due to the parasitoid complex was greater than 97% in 1971 and 75% in 1972. One population in Placer County collapsed in 1971 apparently due to a combination of heat exhaustion and low levels of virus infection. Other defoliators, spiders, and several predatory insect species were collected from the foliage samples simultaneously with the tussock moth during larval sampling. Twelve species of "free living" spiders which could be capable of preying on the defoliator complex of white fir were collected. Parasitoids and predators appear to be potentially important biotic factors at low to moderate host population levels. This is the first recorded case where an agent other than the nucleopolyhedrosis virus has been responsible for the collapse of a Douglas-fir tussock moth population.

scholarly journals Impact of Biochar on Douglas-Fir Tussock Moth (Orgyia pseudotsugata Lepidoptera: Erebidae) Larvae Reared on Synthetic Die

Insects ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1065
Author(s):  
Stacey Rice-Marshall ◽  
Stephen P. Cook ◽  
John Randall
Keyword(s):  
Weight Gain ◽  
Larval Mortality ◽  
Douglas Fir ◽  
High Concentration ◽  
Larval Weight ◽  
Synthetic Diet ◽  
Tussock Moth ◽  
Orgyia Pseudotsugata ◽  
Compensatory Feeding ◽  
Significant Difference

The use of biochar as a soil amendment in forest ecosystems can be beneficial in the restoration of degraded soils. Forest insects such as the Douglas-fir tussock moth, Orgyia pseudotsugata (McDonnough) (Lepidoptera: Erebidae), may be exposed to biochar when the material is applied. Two experiments were conducted using biochar either (1) applied to the surface of the diet at three rates (0, 5, and 10 mg) or (2) incorporated into synthetic diet at four rates (0, 10, 20, and 40% volume/volume). The objective of both experiments was to determine if biochar on the surface or incorporated into a synthetic diet affected development and survival of O. pseudotsugata larvae. In both experiments, there was a significant decrease in estimated time to larval mortality in all biochar treatments compared to untreated controls. In the surface-applied biochar experiment, there was a significant difference in larval weight gain at day 12 between the control and 10 mg biochar treatments. In the experiment with biochar incorporated into the diet, mean larval weight at day 12 was highest in the low (10%) biochar treatment compared to all other treatments, although weight gain was only significantly different between the low- and high-concentration (40%) biochar treatments. Our results suggest that larvae, feeding on a low amount of biochar in the synthetic diet, may respond by engaging in compensatory feeding behavior. Fewer surviving larvae in the biochar treatment groups may contribute to the lack of significance found in the comparison of weight gain at day 24 in each experiment.

PEST MANAGEMENT OF DOUGLAS-FIR TUSSOCK MOTH (LEPIDOPTERA: LYMANTRIIDAE): A SEQUENTIAL SAMPLING METHOD TO DETERMINE EGG MASS DENSITY

1984 ◽  
Vol 116 (7) ◽  
pp. 1041-1049 ◽  
Author(s):  
R. F. Shepherd ◽  
I. S. Otvos ◽  
R. J. Chorney
Keyword(s):  
Sampling Method ◽  
Mass Density ◽  
Sequential Sampling ◽  
Douglas Fir ◽  
Egg Mass ◽  
Tussock Moth ◽  
Incipient Stage ◽  
Orgyia Pseudotsugata ◽  
Detection Tool ◽  
Variability Data

AbstractA sequential egg-mass sample system for Douglas-fir tussock moth, Orgyia pseudotsugata McDunnough (Lepidoptera: Lymantriidae), was designed, based on visual scanning of the lower branches of Douglas-fir trees, Pseudotsuga menziesii (Mirb.) Franco. A branch was removed from each quadrant from the upper, middle and lower crown level, and from the lowest whorl of a total of 59 non-defoliated trees in 10 areas. No consistent trend in egg-mass density per branch could be found between crown levels and no level proved superior as a representative of the tree. Therefore, the lower whorl of branches was selected for survey purposes because of sampling efficiency. Sample stop lines were determined from egg-mass density and variability data collected on 55 sites and subsequent defoliation estimates were related to these densities. The system is designed as an early detection tool to be used only in non-defoliated stands at the incipient stage of an impending outbreak.

TOXICITY OF INSECTICIDES TO DOUGLAS-FIR TUSSOCK MOTH, ORGYIA PSEUDOTSUGATA (LEPIDOPTERA: LYMANTRIIDAE): I. CONTACT AND FEEDING TOXICITY

1979 ◽  
Vol 111 (10) ◽  
pp. 1145-1159 ◽  
Author(s):  
Jacqueline L. Robertson ◽  
Lucille M. Boelter
Keyword(s):  
Rhodamine B ◽  
Douglas Fir ◽  
Relative Toxicity ◽  
Spray Chamber ◽  
Population Response ◽  
Larval Stages ◽  
Tussock Moth ◽  
Orgyia Pseudotsugata ◽  
Rhodamine B Dye ◽  
Spray Volume

AbstractThe toxicities of 14 insecticides to selected larval stages of the Douglas-fir tussock moth were determined with a laboratory spray chamber. The toxicities of 10 were also determined in feeding bioassays. Younger instars were, in general, more susceptible to the toxicants. Significant differences in population response from 1973 to 1977 precluded a rigid interpretation of relative toxicity values in relation to the standard for comparison, DDT. Spray volume, formulation, and the presence of rhodamine B dye significantly affected toxicities of two of the materials, carbaryl and trichlorfon. The degree of exposure of larvae to bioethanomethrin and carbaryl significantly affected mortality.

THE EFFECT OF TEMPERATURE AND FOOD DEPRIVATION ON SURVIVAL OF FIRST-INSTAR DOUGLAS-FIR TUSSOCK MOTHS (ORGYIA PSEUDOTSUGATA) (LEPIDOPTERA: LYMANTRIIDAE)

1983 ◽  
Vol 115 (6) ◽  
pp. 663-666 ◽  
Author(s):  
Roy C. Beckwith
Keyword(s):  
Food Deprivation ◽  
Larval Survival ◽  
Douglas Fir ◽  
Effect Of Temperature ◽  
Rearing Temperature ◽  
Tussock Moth ◽  
Orgyia Pseudotsugata ◽  
First Instar ◽  
Starvation Conditions

AbstractMortality of neonatal Douglas-fir tussock moth larvae varied from 0% to 100% depending on the rearing temperature and duration of food deprivation. Lower temperatures apparently favor larval survival under starvation conditions. For each period of food deprivation, mortality occurs earlier as the temperature increases; this shift to earlier mortality was significant at P <.01. Some implications are discussed.

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