Phenology of White Fir and Douglas-fir Tussock Moth 12 Egg Hatch and Larval Development in California

1976 ◽  
Vol 5 (2) ◽  
pp. 316-322 ◽  
Author(s):  
Boyd E. Wickman
Keyword(s):  
Larval Development ◽  
Douglas Fir ◽  
Egg Hatch ◽  
Tussock Moth ◽  
White Fir

Starch content of conifers defoliated by the Douglas-fir tussock moth

1980 ◽  
Vol 10 (4) ◽  
pp. 535-540 ◽  
Author(s):  
Warren L. Webb
Keyword(s):  
British Columbia ◽  
New Mexico ◽  
Starch Content ◽  
Douglas Fir ◽  
Bud Burst ◽  
Egg Hatch ◽  
Tussock Moth ◽  
Breast Height ◽  
White Fir ◽  
Large Trees

Studies were conducted in British Columbia, Canada, and New Mexico in areas where the tussock moth (Orgyiapseudotsugata (McDunnough)) had heavily defoliated white fir (Abiesconcolor (Gord. and Glend.) Lindl.) and Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) to determine the relation between reserve energy and vigor of stressed trees. Starch, a measure of reserve energy, was found to be reduced in the twigs proportional to the estimated defoliation of sapling-sized trees; starch in the bark at breast height of large trees was also reduced with increased defoliation. Twig starch content did not differ for defoliated Douglas-fir and white fir growing on the same site. Defoliation by the tussock moth accelerated the normal seasonal loss of starch in twigs; this finding was confirmed with artificially defoliated seedlings. Additionally, starch in all vegetative parts of trees was reduced as defoliation intensified. Feeding by tussock moth larvae is expected to reduce reserve energy more if egg hatch closely follows bud burst.

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.

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.

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.

DOUGLAS-FIR TUSSOCK MOTH (HEMEROCAMPA PSEUDOTSUGATA) EGG-MASS DISTRIBUTION ON WHITE FIR IN NORTHEASTERN CALIFORNIA

1967 ◽  
Vol 99 (11) ◽  
pp. 1193-1203 ◽  
Author(s):  
Robert F. Luck ◽  
Donald L. Dahlsten
Keyword(s):  
Sampling Method ◽  
Douglas Fir ◽  
Egg Mass ◽  
Egg Masses ◽  
Sample Unit ◽  
Tussock Moth ◽  
White Fir ◽  
Cardinal Direction ◽  
Sources Of Variation ◽  
Cardinal Directions

AbstractThe distribution of Douglas-fir tussock moth (Hemerocampa pseudotsugata McD.) egg-masses on white fir (Abies concolor (Gord. and Glend.) Lindl.) was studied in three areas of northern California. In each area 100 trees between 4.5 and 8.4 in. in diameter were stratified into five defoliation classes and four crown classes, giving a total of 20 classes per study area with five trees per class. Trees were divided into four crown levels and samples were taken at each of the cardinal directions at each level. Two branches comprised n sample unit in the top half of the tree (eight branches per level) and one branch the sample unit in the bottom half of the tree (four branches per level). Egg masses were recorded per 10 sq. ft of foliage or branch area. Eighty per cent or more of the egg masses were found in the bottom half of the crown. This percentage in the bottom half of the crown increased on trees with heavy defoliation or with increased exposure of the crown. Of the four possible sources of variation considered in this study, crown level, defoliation class, and crown class were significant while cardinal direction was not. A sampling method is proposed on the basis of the information gathered in this investigation.

scholarly journals Evaluation of Thuricide 48Lv Against Douglas-Fir Tussock Moth Reared on Various Host Plants, Laboratory Bioassay, 1992

1995 ◽  
Vol 20 (1) ◽  
pp. 354-354
Author(s):  
Thomas B. Eckberg ◽  
Whitney S. Cranshaw
Keyword(s):  
Host Plants ◽  
Douglas Fir ◽  
Food Type ◽  
Laboratory Bioassay ◽  
Initial Exposure ◽  
Blue Spruce ◽  
Larval Stages ◽  
Tussock Moth ◽  
White Fir ◽  
Petri Dishes

Abstract Trials were conducted to determine the relative susceptibility of different larval stages of Douglas-fir tussock moth to the Bacillus thuringiensis insecticide Thuricide 48LV. Cultures were established from egg masses collected near Vail, CO and larvae were maintained on either white fir, Douglas-fir, or blue spruce foliage. Once larvae were started on a particular host plant, they were fed only that type of food. They were maintained with fresh foliage as needed, and transferred to clean petri dishes when food was changed. Instar II-IV was used for bioassay and were divided into groups of 10, with ten replications for each food type. Foliage was dipped in a 1:400 dilution of Thuricide 48LV, allowed to air dry and subsequently fed to larvae. Mortality was assessed at various intervals between 48 and 213 hours after initial exposure.

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