Tussock Moth Larvae Research Articles

Obligatory multiparasitism in the tussock moth,Orgyia leucostigma

Orgyia leucostigmahaemocytes were able to encapsulate and destroy eggs ofHyposoterspecies, thereby preventing successful parasitism. When host larvae had previously been parasitized byCotesia melanoscela, however, this response was not observed, and 3 differentHyposoterspecies could be reared to maturity in the normally non-permissive host. Appropriate injection experiments established thatC. melanoscelavirus and venom were both required in order for successful parasitism byHyposoterto occur. Covalent cross-linking ofC. melanoscelaviral DNA led to an immune response againstHyposoterlarvae, but not eggs, suggesting that an active viral genome may be required for complete development ofHyposoterspecies in tussock moth larvae.

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

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.

Biochemical comparisons of the peritrophic membranes of the lepidopterans Orgyia pseudotsugata and Manduca sexta

1. 1. The biochemical composition of the peritrophic membrane of both the tobacco hornworm ( Manduca sexta) and Douglas fir tussock moth ( Orgyia pseudotsugata) larvae has been studied. 2. 2. Although the total protein content of the membranes was the same, the amino acid compositions were distinctive for each larval peritrophic membrane. 3. 3. Major M. sexta peritrophic membrane proteins were detected with apparent molecular weights from 32,000 to 210,000 daltons. O. pseudotsugata peritrophic membrane proteins ranged in molecular weight from 20,000 to 220,000 daltons. 4. 4. Periodic acid Schiff (PAS) staining indicated that both membranes contain glycoproteins. 5. 5. The peritrophic membrane of O. pseudotsugata contains approximately twice the amount of hexosamines as that of M. sexta. Both glucosamine and galactosamine are at higher levels in the O. pseudotsugata membrane than in that of M. sexta.

Long-Term Persistence of the Nuclear Polyhedrosis Virus of the Douglas-Fir Tussock Moth, Orgyia pseudotsugata (Lepidoptera: Lymantriidae), in Forest Soil

The long-term persistence of the nuclear polyhedrosis virus of the Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), in forest soil has been established by bioassaying soil and duff samples from an area in which the last tussock moth outbreak took place in 1936–38. Samples were taken from beneath each of 75 white fir, Abies concolor (Gord. and Glend.) Lindl., trees selected within 17 clusters in a study area in the Inyo National Forest, California. Virus was present in 15 soil samples from 9 of the clusters. Although present concentrations of active virus are low (<45 PIB/cm3), enough remains in the mineral soil from sheltered locations to infect tussock moth larvae. Absence of active nuclear polyhedrosis virus in the duff layers above the positive soil samples indicates the duff has accumulated since the last epizootic of tussock moth nuclear polyhedrosis.

HOST FOLIAGE IN THE SUSCEPTIBILITY OF FOREST SITES IN CENTRAL CALIFORNIA TO OUTBREAKS OF THE DOUGLAS-FIR TUSSOCK MOTH, ORGYIA PSEUDOTSUGATA (LEPIDOPTERA: LYMANTRIIDAE)

AbstractHost foliage was evaluated for nonpreference and antibiosis by field rearing Douglas-fir tussock moth larvae, Orgyia pseudotsugata (McDunnough), (instars 2–6) at typical outbreak and non-outbreak forest sites in central California. Nonpreference was evaluated by comparing frass production and antibiosis by comparing survival, pupation, and fecundity on the different sites. Typical outbreak sites had a lower site index and higher plant moisture stress than typical non-outbreak sites. Production of frass for all crown levels collectively was not significantly different between sites, although more frass was produced in the tops of trees on outbreak sites. Survival and pupation were also not significantly different between sites, but egg production was 28% higher on outbreak sites than non-outbreak sites. If differences in foliage quality did exist between sites, they did not affect the tussock moth enough to explain observed differences in population numbers.

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

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.

Action of Douglas Fir Tussock Moth Larvae and Their Microflora on Dietary Terpenes

A single type of bacterium, tentatively identified as a member of the genus Bacillus, was isolated from 2 of 20 midguts of Douglas fir tussock moth larvae being fed a diet of fir needles. No bacteria could be isolated from most midguts. Although spherically shaped bodies were present in the food bolus, these bodies, if microorganisms, could not be distinguished from spherical bodies associated with the plant tissue. The Douglas fir tussock moth dietary terpenes were altered during their passage through the insects, with two new terpenes being detected in the feces. One of these was identified as isoborneol. The relative significance of the insect and gut microflora with respect to terpene modification is unresolved. The well-established toxicity of terpenes may account for the near absence of common gut microflora in the insects.

Some Effects of Douglas Fir Terpenes on Certain Microorganisms

The Douglas fir terpene alpha-pinene was shown to inhibit the growth of a variety of bacteria and a yeast. Other terpenes of the Douglas fir, including limonene, camphene, and isobornyl acetate, were also inhibitory to Bacillus thuringiensis. All terpenes were inhibitory at concentrations normally present in the fir needle diet of Douglas fir tussock moth larvae. The presence of such terpenes in the diet of these insects was found to strongly influence the infectivity of B. thuringiensis spores for the Douglas fir tussock moth larvae. The terpene alpha-pinene destroyed the cellular integrity and modified mitochondrial activity in certain microorganisms.

Apparent replication of an unusual virus-like particle in both a parasitoid wasp and its host.

Nuclear inclusion bodies are found in the hemocytes of all tussock moth larvae parasitized by the braconid wasp Apanteles melanoscelus. These inclusion bodies represent the apparent site of replication of an unusual virus-like particle. Identical particles are observed in the nuclei of a small number of parasitoid calyx cells and are probably transmitted to host larvae during oviposition.

Health hazards to timber and forestry workers from the Douglas fir tussock moth.

A heavy infestation of the tussock moth caterpillar (Orgyia pseudotsugata McDonnough) in forested areas of Oregon was associated with itching of the skin and eyes, nasal discharge, cough, and, at times, respiratory difficulty, Personal interviews and inspection of forty-one occupationally exposed persons were supplemented by a questionnaire administered to 428 individuals, composing three groups at various degrees of risk and a control group. There was a cause and effect relationship between the adverse symptoms and the exposure to tussock moth larvae. The specific etiologic agent was not identified, but it was felt that the secretion, hairs, or other substances in the larvae or cocoons of the moth acted as a potent allergenic substance and, for some persons, was also a primary skin irritant.

Susceptibility of the spruce budworm, Choristoneura fumiferana, and the white-marked tussock moth, Orgyia leucostigmata, to Bacillus thuringiensis: Chemical insecticide combinations

Bacillus thuringiensis mixed with the organophosphate insecticides, fenitrothion (Sumithion), Gardona ®, and Orthene ®, or the synthetic pyrethroid, SBP 1382, was incorporated into synthetic diet and fed larvae of the spruce budworm, Choristoneura fumiferana, and the white-marked tussock moth, Orgyia leucostigma. Mortality was highest when larvae were fed combinations of low concentrations of the insecticides and low to moderate concentrations of the pathogen. The data indicated that applications of a B. thuringiensis dosage expected to produce about 45% mortality of third and fourth instar larvae of the spruce budworm combined with a dosage of fenitrothion causing about 40% mortality or a dosage of Orthene causing from 5 to 25% mortality should result in low budworm survival. With a B. thuringiensis dosage causing 20–60% mortality combined with a fenitrothion dosage causing 15–50% mortality or a sublethal dosage of Gardona, a low survival rate of young white-marked tussock moth larvae may be expected.

Detection of natural infection by cytoplasmic polyhedrosis virus (CPV) occurring in midgut cells of the white-marked tussock moth larvae

Detection of natural infection by cytoplasmic polyhedrosis virus (CPV) occurring in midgut cells of the white-marked tussock moth larvae

Rearing Douglas-Fir Tussock Moth Larvae on Synthetic Media for the Production of Nuclear-Polyhedrosis Virus1

A technique for rearing larvae of the Douglas-fir tussock moth, Hemerocampa pseudotsugata McDunnough, in large numbers on a synthetic medium for the production of nuclear polyhedrons virus is described. The insect was reared from the egg stage generally to the 4th and 5th instar before infection. The larvae appeared normal in every way, reaching an average weight of 310 mg. Mortality during the larval stage prior to infection was very low.

Rearing Douglas-Fir Tussock Moth Larvae on Synthetic Media

A procedure was developed for rearing larvae of Douglas fir tussock moth, Hemerocampa pseudotsugata McDun-nough, in large numbers on a synthetic medium for use laboratory testing of insecticides. The insect was reared from the egg stage generally to the fourth to seventh in-star, depending on testing needs. The larvae appeared normal in every way, reaching a weight of about 300 mg before pupation. An initial high loss from a nuclear polyhedrosis virus in the third instal was avoided by soaking the eggs in a 10% formaldehyde solution. Mortality during the larval stage on media was about 10%. Three thousand larvae were reared per week at a cost (excluding overhead) of about $15. At least 25,000 larvae could be reared weekly by I person working full time.