Orgyia Pseudotsugata Research Articles

Field Evaluation of Baculovirus Stocks Against Douglas-fir Tussock Moth in British Columbia12

Aerial applications of 3 baculovirus stocks were tested against Orgyia pseudolsugata (McDunnough) in British Columbia in June 1975. A dosage of 100 billion polyhedra/acre, formulated in a molasses and a nonmolasses formulation and applied at 1 or 2 gal/acre, provided population control and excellent foliage protection. Larvae collected from the treated areas 5 days after spraying showed virus infection rates that ranged from 60–87%. With the exception of one treatment that was applied under extremely adverse meteorological conditions there were no significant differences between virus treatments. Population densities were reduced by more than 90% at 21 days posttreatment, and no evidence of survival to the pupal stage was found on the virus-treated areas.

Synthesis of aliphatic insect pheromones from alicyclic starting materials: ( Z)-6-heneicosen-11-one and ( z)-8-dodecenyl acetate

Both ( Z)-6-heneicosen-11-one, the pheromone of Douglas fir tussock moth, and ( Z)-8-dodecenyl acetate, the pheromone of oriental fruit moth, have been synthesized from cyclohexane-1,3-dione.

Douglas-Fir Tussock Moth Ground Spray Tests, 1974

Abstract To find a replacement for DDT for control of the Douglas-fir tussock moth ground tests of 15 insecticides were conducted between June 21 and July 10′74 on the Wallowa-Whitman National Forest in northeastern Oregon. Each material was applied at 3 different rates, following recommendations solicited from the manufacturers. Each dosage tested was replicated on 3 randomly selected pairs of trees 15-25 ft high. Applications were made at a rate equal to 1 gal/acre using a backpack mistblower with a Beecomist Model 150 with wettable powder sleeve which gave a droplet size (VMD) of approximately 100 for oil based and 250 for water based sprays. Spraying took 5 days to complete, on each day 3 pairs of trees were randomly selected from those to be treated and set aside as checks. Population estimates were made at 1 day before spraying and 3 intervals after spraying by sampling 3, 18-inch branches from each tree. Populations were expressed as number of larvae per 1000 in of branch surface. Application was made primarily against first and second instar larvae.

Douglas-Fir Tussock Moth Control on Douglas-Fir, 1976

Abstract The test was done on epidemic Douglas-fir tussock moth populations near Kamloops, B.C. Dimilin was applied in a randomized block design by using a conventional boom and nozzle system on fixed-wing aircraft with 22 evenly-spaced tee-Jet nozzles and no. 8010 flat fan spray tips. A mixture of 90% water and 10% ethylene glycol served as carrier. The formulation was sprayed at the rate of 1 gal/acre at 110 mph and 40 psi. The 12 plots ranged in size from 50 to 81 acres and in elevation from 2300 to 2900 ft . Treatments were replicated 3 times and each was applied on June 13, 17, and 18 after complete egg hatch and larval dispersal. Orgyia pseudotsugata larvae were counted on 2 mid crown branch samples from 25 trees in each plot on the day before spray, and 7, 14, 2 1 , 28, and 35 days after spraying. Data were transformed to larvae/1000 in2 of Douglas-fir foliage and subjected to analysis of variance and analysis of covariance.

Laboratory and Field Bioassay of the Douglas-fir Tussock Moth 1 Pheromone, (Z)-6-Heneicosen-11-One 2

Laboratory bioassay demonstrated that the pheromone (Z)-6-heneicosen-11-one, its (E)-stereoisomer, and an epoxide (Z)-6,7-epoxyheneicosan-11-one are all attractive to the male Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough). The pheromone was approximately 27 times more attractive than the (E)-isomer and 300 times more attractive than the epoxide. An alcohol, (Z)-6-heneicosen-11-ol, was found to have a weak inhibitory effect on pheromone response. In the field, dosages of synthetic pheromone as low as 10-ng captured males and 50-ng baits were still attractive after 7 days' exposure. A controlled-release formulation, emitting pheromone at an estimated rate of 4 ng/min at 25°C, approached but did not equal the attractiveness of a live female. It is likely that an additional compound is present in the natural pheromone that is required to optimize response to the synthetic preparation. (Z)-6-heneicosen-11-one is also an effective attractant for the western tussock moth, O. cana Edwards, the rusty tussock moth O. antiqua (Linn.), Dasychira vagans grisea (Barnes and McDunnough) and D. grisefacta ella Bryk.

Field Evaluations of Acephate and Dimilin™ Against the Douglas-fir Tussock Moth12

Efficacy of acephate at 1.0 and 0.5 lb AI/2 gal/acre against Orgyia pseudotsugata (McDunnough) was compared to DDT at 0.75 lb AI/gal/acre on replicated 20 acre plots in 1974. Acephate at 1.0 lb AI/gal/acre and Dimilin™{ [1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl) urea] at 0.25 lb AI/gal/acre were evaluated on replicated 150-acre plots in 1975. In both experiments, all treatments caused significant reductions in larval populations. In 1974, the 1.0 lb acephate treatment resulted in populapation reductions which were comparable to the DDT treatment; however, the larval knockdown was faster for DDT. Both acephate and Dimilin provided excellent population control and foliage protection in 1975.

Life Tables for a Declining Population of the Douglas-fir Tussock Moth1 in Northeastern Oregon3

Changes in population density and their causes were quantified on 22 sample plots representing 4 different defoliation intensities in a Douglas-fir tussock moth outbreak. Density of larvae was extraordinarily high at the beginning of feeding in June 1973. Thereafter, populations either declined sharply or completely collapsed on all of the plots studied. Measurable larval populations of the subsequent generation were found on only 6 plots in June 1974, and these had virtually disappeared by midsummer. Rate of decline was variable under different conditions but appeared to be predictable from the level of past defoliation. In general, the decline rate was faster on heavily or moderately defoliated plots than on lightly or proviously undefoliated plots. Population collapse was the result of a multitude of natural factors operating in compensating ways against the high density outbreak. It was characterized by an increase in the effect of numerous mortality factors including virus disease, insect parasites, predators, starvation, and larval dispersion, as well as changes in population quality and structure resulting in lower fecundity, egg quality and a change in sex ratio. The largest proportion of mortality occurred early in the larval cycle and was probably due to losses from natural dispersion and predation; however, other factors may have had an equal or greater effect on ultimate collapse of the population although they accounted for less total mortality.

A synthesis of (Z)-6-heneicosen-11-one. The sex pheromone of the Douglas fir tussock moth.

A synthesis of (Z)-6-heneicosen-11-one. The sex pheromone of the Douglas fir tussock moth.

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

The phenology of bud burst and shoot elongation of the host tree and egg hatch and larval development were studied on 3 areas in a 1972 infestation. Bud burst and egg hatch were found to be closely related to accumulated degree-days, and peak egg hatch occurred when 77–97% of the buds had burst. Larval development then closely followed shoot elongation. This synchrony of host and insect phenology provides an easily observed field event for monitoring Douglas-fir tussock moth development.

Field Efficacy of Aerial Applications of Carbaryl Against Douglas-fir Tussock Moth13

Sevin 4-oil, an oil suspension of carbaryl, was applied by helicopter to forested areas infested by Orgyia pseudotsugata (McDunnough), in western Montana and northern Idaho. Dosage was 2 lb AI/0.75 gal of carrier/acre. Spray was applied to 1st instars in Montana and 3rd and 4th instars in Idaho. Treatments provided a high degree of insect mortality and measurable foliage protection; the residual population did not produce egg masses in sufficient quantity to repopulate infested areas.

Influence of Host Foliage on the Douglas-fir Tussock Moth 1

Douglas-fir tussock moth (Orgyia pseudotsugata (McDunnough)) larvae were fed foliage obtained from the top and bottom of the crowns of Douglas-fir, grand fir, and subalpine fir under controlled laboratory conditions. High density field populations were simulated by forcing larvae to feed upon old-growth foliage creating a stress factor that was detrimental to the population. The host plant and crown position had a significant effect on frass production, head-capsule size, and pupal weight. The number of eggs produced was significantly greater from foliage obtained from the top of the crown. The most significant factor was whether larvae were forced to feed upon old-growth foliage. This “stress” resulted in increased development time, frass production, number of instars and decreased head capsule size, and egg production.

Flight, Attraction, and Mating Behavior of the Douglas-fir Tussock Moth 1 in Oregon 2

Continuous observations and measurements were made of adult flight, mating, and oviposition of Orgyia pseudotsugata McDunnough over a 31-h period in eastern Oregon. Male flight started at 1000 (P.S.T.), gradually increased to a peak period ca. 1700, and concluded at 1930. This coincided with peak mating activity with the wingless females. Oviposition occurred immediately after mating. Virgin females attached to sticky traps were very effective for attracting and capturing male moths. The female sex pheromone offers a possible technique for early detection of Douglas-fir tussock moth populations.

Synthesis of (Z)-6-heneicosen-11-one. Douglas fir tussock moth sex attractant

Synthesis of (Z)-6-heneicosen-11-one. Douglas fir tussock moth sex attractant

Douglas-fir tussock moth: sex pheromone identification and synthesis.

The sex pheromone of the Douglass-fir tussock moth Orgyia pseudotsugata (McDunnough) has been isolated and identified as (Z)-6-heneicosen-11-one. This compound and its E isomer have been synthesized and are highly potent in laboratory bioassays and field trials.

Aerial Applications of a Nucleopolyhedrosis Virus and Bacillus thuringiensis Against the Douglas Fir Tussock Moth12

Efficacy of applications of a nucleopolyhedrosis virus (NPV) and Dipel (Bacillus thuringiensis Berliner) against Orgyia pseudotsugata (McDunnough) was determined on replicated field plots of 20 acres in size. Population reductions exceeded 95% at 35 days on plots treated with NPV dosages of 100×109 and at 100×1010 polyhedra/acre in 2 gal/acre of a 25% molasses formulation. Application of Dipel at 1 lb/acre in 25% molasses was as effective as the NPV. These treatments also provided excellent foliage protection, with estimated defoliation levels below 25%. In contrast, Dipel formulated in BioFilm® failed to reduce larval densities to a satisfactory level or to prevent severe defoliation.

Economics, Esthetics, Environment, and Entomologists: The Tussock Moth Dilemma 1

The author reviews the life cycle and impact of Hemerocampa pseudotsugata McDunnough and the variety of known and assumed factors involved in the decision to use DDT during 1974 to control the outbreak in Washington, Idaho, and Oregon. Potential alternate control procedures are listed. While the issue is complicated, fault is found in the response of agencies, environmentalists, and entomologists to the serious threat presented by this extensive outbreak of the tussock moth.

POPULATION CHANGE IN AN OUTBREAK OF THE DOUGLAS-FIR TUSSOCK MOTH, ORGYIA PSEUDOTSUGATA (LEPIDOPTERA: LYMANTRIIDAE), IN CENTRAL ARIZONA

AbstractChanges in population density were evaluated over an outbreak cycle of the Douglas-fir tussock moth. Growth rate of populations was independent of larval density in the first year, but thereafter became a reciprocal function of density, terminated by complete population collapse at the end of the third year. Through correlation analyses, it was found that density of small larvae accounted for a large proportion of the change in population density between years. This suggests that the local infestations developed largely from resident populations of at least 2 years and not from spread of early instar larvae during the outbreak.

Insect Defoliation as a Predisposing Agent to a Bark Beede Outbreak in Eastern Montana

Most of the economically important genera of North American Scolytidae commonly infest trees weakened by a variety of agents including drought, natural disasters, diseases, or old age, and are therefore considered secondary insects (Rudinsky 1962). Outbreaks of defoliating insects have occasionally weakened trees to the point they have become susceptible to secondary bark beetle invasion. For example, secondary bark beetles killed 16.7% of the ponderosa pine ( Pinus ponderosa Laws.) defoliated by the pine butterfly, Neophasia menapia Felder & Felder, in central Idaho (Evenden 1940). Similarly, defoliation of white fir, Abies concolor (Lindl.), by the Douglas-fir tussock moth, Orgyia pseudotsugata McDunnough, in California was followed by infestations of the fir engraver, Scolytus ventralis LeConte, and a roundheaded borer, Tetropium abietis Fall (Wickman 1963). Unfortunately, the intensity of defoliation associated with such bark beetle outbreaks has seldom been documented and as a result we lack information on the degree of defoliation likely to render trees susceptible to bark beetle attack.

Douglas-Fir Tussock Moth:1 Contact Toxicity of 20 Insecticides Applied to the Larvae13

Twenty chemicals were tested for their toxicity to 4th-instars of Hemerocampa pseudotsugata McDunnough. Eleven were more toxic than the standard, mexacarbate, at both LD50 and LD90. They were, in decreasing order of toxicity at LD50 bioethanomethrin, NIA 26021 ([+] cis stereo isomer of resmethrin), NIA 18739 ([+] trans stereo isomer of resmethrin), resmethrin, methomyl, phoxim, DDTpp′, chlormethylfos, and Phosvel ®([2, 5-dichloro-4-bromophenyl) O-methyl phenyl thiophosphate). The descending order of toxicity at LD90 was: bioethanomethrin, NIA 26021, NIA 18739, resmethrin, methomyl, phoxim, chlorphoxim, pyrethrins, DDTpp′, chlormethylfos, and Phosvel. The cis isomer of resmethrin was significantly more toxic at both LD50 and LD90 than the trans isomer. Data also were obtained on the effect of posttreatment holding conditions and on the effect of dye tracers and stabilizing adjuvants on the insecticidal activity of pyrethrins.

POPULATION DYNAMICS OF THE FIR ENGRAVER, SCOLYTUS VENTRALIS (COLEOPTERA: SCOLYTIDAE): I. ANALYSIS OF POPULATION BEHAVIOR AND SURVIVAL FROM 1964 TO 1971

AbstractPopulations of the fir engraver reached epidemic proportions and then declined to a very low level over the study period (1964–71). However, population density within infested trees showed an inverse relationship to overall population trend. The population trend over the past 40 years was associated to some degree with rainfall deficits and with Douglas-fir tussock moth outbreaks.The major contribution to total mortality in each generation occurred in the larval, pupal and pre-emergent adult stages, next was adult mortality and infecundity, while egg mortality was of least significance. Mortality and infertility of parent females was mainly caused by nematode parasites although host resistance resulted in a significant number of attack failures. Parasitism by a phorid fly was of minor importance. Nematode parasitism appeared to be density-dependent in relation to overall population size.Most egg mortality resulted from host resistance which was inversely related to egg density within trees. Other egg mortality occurred in a density-independent manner.Mortality between larva and brood adult stages was mainly attributed to intra- and interspecific competition. The impact of these factors was directly related to within-tree larval density. Nematode parasitism was related to overall fir engraver population size and to per cent infection of attacking females. Predator activity was weakly density-dependent and mortality caused by resinosis was inversely related to fir engraver density. Parasitism and other mortality factors appeared to be independent of host density.An hypothesis is presented for the population behavior of the fir engraver; population fluctuations being determined by the quantity of susceptible trees and ultimately regulated by intraspecific competition. Nematode parasitism and interspecific competition were regarded as modifying, and perhaps sometimes regulating, abundance. Areas needing additional study, particularly host-tree physiology are discussed.