Orgyia Leucostigma Research Articles

Field Test of the Propheromones of the Whitemarked Tussock Moth (WMTM) Orgyia leucostigma (J.E. Smith) (Lepidoptera: Erebidae).

The whitemarked tussock moth (WMTM), Orgyia leucostigma (J.E. Smith) (Lepidoptera: Erebidae), is an economic pest in Nova Scotia, Canada, where it undergoes periodic outbreaks defoliating several tree species of economic value, including balsam fir, Abies balsamea (L.) Miller (Pinaceae). Herein is described a releasing device for the WMTM sex pheromone (Z,Z)-6, 9-heneicosadien-11-one based on a rubber septum, which converts pheromone precursors, such as acetals, namely (Z,Z)-11,11-dimethoxy-6,9-heneicosadiene and (Z,Z)-6,9-heneicosadien-11-one ethylene ketal, to the pheromone itself by the action of acetic acid and releases it over time. The pheromone is unstable in nature and, consequently, lures made with this compound will only attract WMTM for a day or two. The two pheromone precursors, however, are more stable, and are converted slowly into the pheromone by acetic acid impregnated in the releasing device, or by acidic conditions in the environment. The two pheromone precursors were synthesized in 2019 using a modified, previously published approach. Field trapping studies conducted from 2019-22 showed that traps baited with rubber septa loaded with either (Z,Z)-11,11-dimethoxy-6,9-heneicosadiene by itself or (Z,Z)-6,9-heneicosadien-11-one ethylene ketal plus acetic acid consistently caught significantly more WMTM than traps baited with blank septa in most experiments.

CRISPR/Cas9 disruption of UGT71L1 in poplar connects salicinoid and salicylic acid metabolism and alters growth and morphology.

Salicinoids are salicyl alcohol-containing phenolic glycosides with strong antiherbivore effects found only in poplars and willows. Their biosynthesis is poorly understood, but recently a UDP-dependent glycosyltransferase, UGT71L1, was shown to be required for salicinoid biosynthesis in poplar tissue cultures. UGT71L1 specifically glycosylates salicyl benzoate, a proposed salicinoid intermediate. Here, we analyzed transgenic CRISPR/Cas9-generated UGT71L1 knockout plants. Metabolomic analyses revealed substantial reductions in the major salicinoids, confirming the central role of the enzyme in salicinoid biosynthesis. Correspondingly, UGT71L1 knockouts were preferred to wild-type by white-marked tussock moth (Orgyia leucostigma) larvae in bioassays. Greenhouse-grown knockout plants showed substantial growth alterations, with decreased internode length and smaller serrated leaves. Reinserting a functional UGT71L1 gene in a transgenic rescue experiment demonstrated that these effects were due only to the loss of UGT71L1. The knockouts contained elevated salicylate (SA) and jasmonate (JA) concentrations, and also had enhanced expression of SA- and JA-related genes. SA is predicted to be released by UGT71L1 disruption, if salicyl salicylate is a pathway intermediate and UGT71L1 substrate. This idea was supported by showing that salicyl salicylate can be glucosylated by recombinant UGT71L1, providing a potential link of salicinoid metabolism to SA and growth impacts. Connecting this pathway with growth could imply that salicinoids are under additional evolutionary constraints beyond selective pressure by herbivores.

Quantifying Insect Predation in Laboratory Arenas: the Effect of Prey Acclimation

There are drawbacks associated with current methods used to quantify insect predation. However, there has been relatively little effort to experimentally document the sources of biases associated with different methodologies. In this study, we investigated how methods used experimentally to quantify predation may influence insect antipredator defenses being observed, and thus alter the determination of the number of prey killed by predators, and potentially the conclusions reported in the study. We focused on acclimation period, which represents the time between the point at which a prey individual is made available, for example on a leaf, and when the experiment is initiated. In essence, this is the period of time during which an organism adjusts to the conditions that surround it before a treatment is imposed. We investigated if prey acclimation period on plants influences the antipredator behavior of larval Orgyia leucostigma (J.E. Smith) (Lepidoptera: Lymantriidae), and the number of prey killed in the laboratory by the predatory wasp Polistes fuscatus (Fabricius) (Hymenoptera: Vespidae). The results of this study provide evidence that acclimation time significantly affects the antipredator behavior observed and mortality of caterpillars exposed to predators. The majority of larvae allowed short acclimation periods did not drop in response to the attacks of wasps. These larvae suffered significantly higher mortality compared to caterpillars that were allowed to acclimate for longer periods of time.

A new synthesis of (Z,Z)-11,11-dimethoxy-6,9-heneicosadiene and 2-((Z,Z)-1,4-decadienyl)-2-ndecyl-1,3-dioxolane, precursors of (Z,Z)-6,9-heneicosadien-11-one, a pheromone component of the whitemarked tussock moth, Orgyia leucostigma (J.E. Smith) (Lepidoptera: Erebidae)

The straightforward synthesis of two long-chain diene ketals, (Z,Z)-11,11-dimethoxy-6,9-heneicosadiene and 2-ndecyl-2-((Z,Z)-1,4-decadienyl)-1,3-dioxolane, is described. These two ketals are synthetic propheromones, or pheromone precursors, of the whitemarked tussock moth (WMTM, Orgyia leucostigma (J.E. Smith) (Lepidoptera: Erebidae)), whose unstable female-produced sex pheromone component, (Z,Z)-6,9-heneicosadien-11-one, lasts only 1–2 days in traps in the field. The two propheromones were synthesized by terminal alkyne/propargylic bromide couplings, facilitated by cesium carbonate, which assembled the 21-carbon chains with skipped diynes. Semi-reduction of the diynes gave the requisite dienes. These two diene ketals were then formulated into lures, which converted them in situ into the attractive (Z,Z)-6,9-heneicosadien-11-one. The performance of these lures is briefly described.

Orgyia leucostigma (white-marked tussock moth)

Orgyia leucostigma (white-marked tussock moth)

The Interactive Effect of Elevated CO2 and Herbivores on the Nitrogen-Fixing Plant Alnus incana ssp. rugosa.

Many studies have found that future predicted CO2 levels can increase plant mass but dilute N content in leaves, impacting antiherbivore compounds. Nitrogen-fixing plants may balance their leaf C:N ratio under elevated CO2, counteracting this dilution effect. However, we know little of how plants respond to herbivores at the higher CO2 levels that occurred when nitrogen-fixing plants first evolved. We grew Alnus incana ssp. rugosa was grown at 400, 800, or 1600 ppm CO2 in soil collected from the field, inoculated with Frankia and exposed to herbivores (Orgyia leucostigma). Elevated CO2 increased nodulated plant biomass and stimulated the nitrogen fixation rate in the early growth stage. However, nitrogen-fixing plants were not able to balance their C:N ratio under elevated CO2 after growing for 19 weeks. When plants were grown at 400 and 1600 ppm CO2, herbivores preferred to feed on leaves of nodulated plants. At 800 ppm CO2, nodulated plants accumulated more total phenolic compounds in response to herbivore damage than plants in the non-Frankia and non-herbivore treatments. Our results suggest that plant leaf defence, not leaf nutritional content, is the dominant driver of herbivory and nitrogen-fixing plants have limited ability to balance C:N ratios at elevated CO2 in natural soil.

Anti-Herbivore Activity of Oregonin, a Diarylheptanoid Found in Leaves and Bark of Red Alder (Alnus rubra).

Plants synthesize a wide range of bioactive secondary metabolites to defend against pests and pathogens. Red alder (Alnus rubra) bark, root, and leaf extract have a long history of use in traditional medicine and hygiene. Diarylheptanoids, especially oregonin ((5S)-1,7-bis(3,4-dihydroxyphenyl)-5-(β-D-xylopyranosyloxy)-heptan-3-one), have been identified as major bioactive constituents. Diarylheptanoids have become a focus of research following reports of their antioxidant, antifungal, and anti-cancer activities. Recent data suggest that high oregonin concentration is associated with resistance of red alder leaves to western tent caterpillar (Malacosoma californicum) defoliation. Here we test effects of this compound directly on leaf-eating insects. Purified oregonin was examined in insect choice and toxicity tests using lepidopteran caterpillars. The compound exhibited significant anti-feedant activity against cabbage looper (Trichoplusia ni), white-marked tussock moth (Orgyia leucostigma), fall webworm (Hyphantria cunea), and M. californicum at concentrations corresponding to oregonin content of the most resistant alder clones in previous experiments. Toxicity tests were carried out with cabbage looper larvae only, but no contact or ingested toxicity was detected. Our results suggest that oregonin at levels found in red alder leaves early in the growing season may contribute to protecting red alder from leaf-eating insects.

Screening potential pests of Nordic coniferous forests associated with trade in ornamental plants

Plant pests moved along with the trade in ornamental plants could pose a threat to forests. In this study plant pests potentially associated with this pathway were screened to identify pests that could pose a high risk to the coniferous forests of Finland, Sweden and Norway. Specifically, the aim was to find pests that potentially could fulfil the criteria to become regulated as quarantine pests. EPPO’s commodity study approach, which includes several screening steps, was used to identify the pests that are most likely to become significant pests of Picea abies or Pinus sylvestris. From an initial list of 1062 pests, 65 pests were identified and ranked using the FinnPRIO model, resulting in a top list of 14 pests, namely Chionaspis pinifoliae, Coleosporium asterum s.l., Cytospora kunzei, Dactylonectria macrodidyma, Gnathotrichus retusus, Heterobasidion irregulare, Lambdina fiscellaria, Orgyia leucostigma, Orthotomicus erosus, Pseudocoremia suavis, Tetropium gracilicorne, Toumeyella parvicornis, Truncatella hartigii and Xylosandrus germanus. The rankings of the pests, together with the collected information, can be used to prioritize pests and pathways for further assessment.

The genome of a baculovirus isolated from Hemileuca sp. encodes a serpin ortholog

The genome sequence of a baculovirus from Hemileuca sp. was determined. The genome is 140,633kb, has a G+C content of 38.1%, and encodes 137 putative open-reading frames over 50 amino acids. 126 of these ORFs showed similarity to other baculovirus genes in the database including all 37 core genes. Of the remaining 11 predicted genes, one is related to a lepidopteran serpin gene. This is the first report of a baculovirus encoding a member of this family of serine protease inhibitors, and to our knowledgethe first report of a viral serpin outside the Poxviridae. The genome also contained three homologous repeat sequences. Phylogenetic analysis indicated that the virus is a group II Alphabaculovirus and belongs to a lineage that includes Orgyia leucostigma, Ectropis obliqua, Apocheima cinerarium, and Euproctis pseudoconspersa nucleopolyhedroviruses.

Larval diet prior to and following virus ingestion influences the efficacy of two nucleopolyhedroviruses in whitemarked tussock moth (Orgyia leucostigma) caterpillars

AbstractFood quality can influence the performance of immature insects and their interactions with pathogens, such as viruses. In manipulative field studies, virus-free caterpillars of the whitemarked tussock moth (WMTM) (Orgyia leucostigma (Smith)) had higher survival, more female-biased sex ratios, and were larger when feeding on white birch (Betula papyrifera Marshall) versus balsam fir (Abies balsamea (Linnaeus) Miller) or red spruce (Picea rubens Sargent). Subsequent laboratory studies with two nucleopolyhedroviruses, derived from WMTMs and Douglas-fir tussock moths, indicated that caterpillars fed high quality food (i.e., artificial diet) prior to infection had less mortality associated with virus infection than those feeding on lower quality foliage (i.e., birch). In field studies, caterpillars fed birch following infection had significantly lower mortality than those feeding on relatively lower quality foliage (i.e., balsam fir). We postulate that higher nutritional quality in artificial diet relative to birch (previrus-ingestion nutrition) and in birch relative to balsam fir foliage (postvirus-ingestion nutrition) has a positive effect on the ability of tussock moth caterpillars to resist or recover from viral infections, although the specific mechanisms responsible for observed resistance remain unclear.

Insect cell lines and baculoviruses as effective biocontrol agents of forest pests

Background Canada is a nation of trees. Canadian forests cover 50% of Canada’s land area and represent 10% of world’s forested area. Canada exports more processed forest products than any other country. It is also a host to a variety of forest insects both native and non native that limit the economic, recreational and wildlife habitat use. Our research focuses on initiating insect cell lines, determining nutritional requirements of cells, and developing low cost media for large scale propagation of insect pathogenic viruses as ecologically sound alternatives to chemical pesticides. Cell lines are used for bioassay and strain selection of viruses and bacterial toxins and for production of foreign gene products using baculovirusand entomopoxvirus expression vectors. They offer a cleaner, viable alternative to insect larvae for producing viral pesticides. Since 1969, over 150 continuous cell lines have been produced for forest insect pest research at GLFC. This collection represents one of largest single site repository of frozen insect cell lines in the world. Cell lines developed include tissues of the eastern spruce budworm (Choristoneura fumiferana), western spruce budworm (Choristoneura occidentalis), forest tent caterpillar (Malacosoma disstria), tobacco hornworm (Manduca sexta), white-marked tussock moth (Orgyia leucostigma), red-headed pine sawfly (Neodiprion lecontei), gypsy moth (Lymantria dispar), white pine weevel (Pissodes strobi), the tarnished plant bug (Lygus lineolaris) and the ash and privet borer (Tylonotus bimaculatus). These cell lines represent six tissues of origin, namely neonate larvae, pre-pupae, embryos, ovaries, hemocytes, and midgut and four Insect Orders namely Lepidoptera, Hymenoptera, Coleoptera and Hemiptera. Presently, cell lines developed at GLFC are being used by 41 researchers in 8 Canadian provinces, 42 researchers in 21 US States and 28 researchers in 12 countries worldwide.

Complete Sequence, Analysis and Organization of the Orgyia leucostigma Nucleopolyhedrovirus Genome

The complete genome of the Orgyia leucostigma nucleopolyhedrovirus (OrleNPV) isolated from the whitemarked tussock moth (Orgyia leucostigma, Lymantridae: Lepidoptera) was sequenced, analyzed, and compared to other baculovirus genomes. The size of the OrleNPV genome was 156,179 base pairs (bp) and had a G+C content of 39%. The genome encoded 135 putative open reading frames (ORFs), which occupied 79% of the entire genome sequence. Three inhibitor of apoptosis (ORFs 16, 43 and 63), and five baculovirus repeated ORFs (bro-a through bro-e) were interspersed in the OrleNPV genome. In addition to six direct repeat (drs), a common feature shared among most baculoviruses, OrleNPV genome contained three homologous regions (hrs) that are located in the latter half of the genome. The presence of an F-protein homologue and the results from phylogenetic analyses placed OrleNPV in the genus Alphabaculovirus, group II. Overall, OrleNPV appears to be most closely related to group II alphabaculoviruses Ectropis obliqua (EcobNPV), Apocheima cinerarium (ApciNPV), Euproctis pseudoconspersa (EupsNPV), and Clanis bilineata (ClbiNPV).

Effect of the Growth Regulator Paclobutrazol and Fertilization on Defensive Chemistry and Herbivore Resistance of Austrian Pine (Pinus nigra) and Paper Birch (Betula papyrifera)

The Growth/Differentiation Balance Hypothesis predicts that environmental factors that limit growth of plants more than their rate of photosynthesis should increase secondary metabolism and resistance to insects. Soil drench application of the plant growth regulator paclobutrazol slowed the growth of paper birch (Betula papyrifera) and Austrian pine (Pinus nigra) with no effect on photosynthesis. In response, foliar concentrations of condensed tannins (but not total phenolics) in birch increased as predicted, which increased birch resistance to gypsy moth (Lymantria dispar) and whitemarked tussock moth (Orgyia leucostigma), but only during the second season after treatment. In both years, there was a negative correlation between foliar concentrations of total phenolic and condensed tannins and growth of paper birch, which is consistent with the predicted trade-off between growth and defense. Conversely, in Austrian pine, paclobutrazol and fertilization did not have an effect on foliar concentration of tannins, phenolics, and terpenes, nor did the treatments have any effect on resistance to European pine sawfly (Neodiprion sertifer). Hence, the effects of paclobutrazol on tree growth, defensive chemistry, and insect resistance were species-specific and time sensitive.

Contact with caterpillar hairs triggers predator-specific defensive responses

Organisms have evolved morphological and behavioral traits that reduce their susceptibility to predation. However, few studies have considered how morphological structures work to provide informational inputs necessary for effective behavioral responses to predation risk. In this study, we demonstrate that the hairs of Orgyia leucostigma (Lymantriidae) caterpillars not only function as physical barriers that deter predators but also act to provide sensory inputs triggering behavior that reduces predation risk. In particular, the way in which caterpillars respond when their hairs are touched is predator specific. Mechanical parameters of the interaction determining the response were identified correlatively and confirmed manipulatively. Caterpillars predominantly dropped in response to high hair bending velocities and predominantly walked away in response to low hair bending velocities. These stimulus-specific responses appear to be adaptive as they led to increased survival. Our results demonstrate a functional link between morphology and behavior. The ability to respond effectively only after the initiation of a predator attack should reduce the costs associated with antipredator behaviors. Copyright 2011, Oxford University Press.

Endogenous overexpression of Populus MYB186 increases trichome density, improves insect pest resistance, and impacts plant growth

Trichomes are specialized epidermal cells that generally play a role in reducing transpiration and act as a deterrent to herbivory. In a screen of activation-tagged Populus tremula × Populus alba 717-1B4 trees, we identified a mutant line, fuzzy, with increased foliar trichome density. This mutant also had a 35% increase in growth rate and a 200% increase in the rate of photosynthesis as compared with wild-type poplar. The fuzzy mutant had significant resistance to feeding by larvae of the white-spotted tussock moth (Orgyia leucostigma), a generalist insect pest of poplar trees. The fuzzy trichome phenotype is attributable to activation tagging and increased expression of the gene encoding PtaMYB186, which is related to Arabidopsis thaliana MYB106, a known regulator of trichome initiation. The fuzzy phenotype can be recapitulated by overexpressing PtaMYB186 in poplar. PtaMYB186 overexpression results in reconfiguration of the poplar transcriptome, with changes in the transcript abundance of suites of genes that are related to trichome differentiation. It is notable that a plant with misexpression of a gene responsible for trichome development also had altered traits related to growth rate and pest resistance, suggesting that non-intuitive facets of plant development might be useful targets for plant improvement.

Soil carbon and nitrogen mineralization following deposition of insect frass and greenfall from forests under elevated CO2 and O3

Elevated CO2 and O3 alter tree quality and the quality of herbivore inputs, such as frass, to forest soil. Altered quality or quantity of herbivore inputs to the forest floor can have large impacts on below- ground processes. We collected green leaves and frass from whitemarked tussock moth caterpillars from aspen-birch stands at the Aspen Free Air CO2 Enrichment (FACE) site near Rhinelander, WI, USA. Small or large quantities of frass, greenfall, or a 1:1 ratio of frass and greenfall were added to microcosms for each FACE treatment (control, +CO2 ,+ O 3, +CO2+O3). We measured initial frass and greenfall quality, and recorded microbial respiration, and nitrate leaching over 40 days. Elevated carbon dioxide (eCO2) and tropospheric ozone (eO3) significantly altered the carbon, nitrogen, and condensed tannin content of insect frass and green leaves. Although FACE treatments affected input quality, they had minimal effect on microbial respiration and no effect on nitrogen leaching. In contrast, input quantity substantially influenced microbial respiration and nitrate leaching. Respiratory carbon loss and nitrate immobilization were nearly double in microcosms receiving large amounts of herbivore inputs than those receiving no herbivore inputs. Small amounts of herbivore inputs, however, did not significantly alter microbial respiration or immobilization, suggest- ing that effects of herbivore inputs on soil processes will be detected only at moderate to high herbivory/ input levels. These results suggest that subtle changes in frass and greenfall quality may not affect soil nutrient cycling. In contrast, environmental change induced increases in insect population size or frass and greenfall inputs to the soil may substantially impact nutrient cycling.

Can alien plants support generalist insect herbivores?

Simple rearing experiments were con- ducted to address two questions relevant to under- standing how generalist lepidopteran herbivores interact with alien plants. Yellow-striped armyworm (Spodoptera ornithogalli), luna moth (Actias luna), bagworm (Thyridopteryx ephemeraeformis) and white-marked tussock moth (Orgyia leucostigma) were reared from egg to 5th instar on excised foliage in the laboratory to determine the degree to which highly polyphagous lepidopteran herbivores are physiologically capable of surviving and developing on the suite of alien plants naturalized in the mid- Atlantic. Actias luna larvae from a single population were similarly reared on a representative of each of the 25 native plant genera recorded as hosts for this species to compare the diet breadth of a local population with that listed over the entire geographic range of the species. With few exceptions, all four generalists either quickly starved or grew at an unsustainably low rate on alien foliage. Actias luna larvae survived for 18 days on only 44% of the native plants recorded as hosts over the entire range of this insect and thrived on only 7%. The data suggest that (1) alien plants are unlikely to produce as much generalist insect biomass as the native plants they replace and (2) Lepidoptera that qualify as generalists when host breadth is considered over their entire geographic range may express a far more specialized diet within local populations. Both of these conclu- sions support the hypothesis that alien plant invasions may seriously disrupt terrestrial food webs by reducing the insect biomass required by insectivores in higher trophic levels.

Foliage‐age mixing within balsam fir increases the fitness of a generalist caterpillar

Abstract.1. Manipulative field studies were carried out to evaluate the foliage age preference–performance relationship for an extreme generalist herbivore, the whitemarked tussock moth (Orygia leucostigma Smith) (Lepidoptera: Lymantriidae), within balsam fir [Abies balsamea (L.) Mill].2. Field surveys indicated that early instar caterpillars fed almost exclusively on young (i.e. current‐year) foliage, whereas late instars caterpillars fed on both young and mature (i.e. 1‐ and 2‐year‐old) foliage.3. Survival of early instar caterpillars was highest in treatments where current‐year and/or 1‐year old foliage were available, but decreased significantly on older foliage. In contrast, late instar caterpillars had the highest survival when allowed to feed on all age classes of foliage, whereas potential fecundity was highest for late instars that fed on young foliage.4. Overall, caterpillars had 32–65% higher fitness when able to feed on all rather than just one age class of foliage.5. These results support both the ‘complementary diet' hypothesis, which states that dietary mixing of different‐aged foliage can increase nutrient uptake and/or dilute harmful secondary plant chemicals, and the ‘ontogeny’ hypothesis, which attributes changes in diet to changes in the nutritional needs and/or tolerance to plant defences of juvenile insects as they develop.

Scaling of Individual Phosphorus Flux by Caterpillars of the Whitemarked Tussock Moth,Orygia leucostigma

We conducted a laboratory study to evaluate the effects of body mass, environmental temperature, and food quality on phosphorus (P) efflux by caterpillars of the whitemarked tussock moth, Orygia leucostigma, J. E. Smith (Lepidoptera: Lymantriidae). We found that individual phosphorus efflux rate (Q the rate at which excreted and unassimilated P was egested in frass, mgP/day) was related to larval mass (M, mg dry) and environmental temperature (T,K) as Q = e14.69 M1.00e-0.54/kT, where K is Boltzmann's constant (8.62 × 10-5 eV/K, 1 eV = 1.60 × 10-19J). We also found that P efflux was not related to food phosphorous concentration, and suggest that this result was due to compensatory feeding by larvae eating low quality leaves. The P efflux model resulting from this analysis was simple and powerful. Thus, it appears that this type of model can be used to scale P flux from individual larvae to the population level and link species of insect herbivores to ecosystem processes.

Monitoring and Temperature-Based Prediction of the Whitemarked Tussock Moth (Lepidoptera: Lymantriidae) in Blueberry

Larvae of the whitemarked tussock moth, Orgyia leucostigma (J.E. Smith) (Lepidoptera: Lymantriidae), defoliate and contaminate blueberries, Vaccinium corymbosum L., in eastern North America, but infestations are often not detected until economic damage has been caused. To improve monitoring techniques and understand the phenology of the whitemarked tussock moth in blueberry, we compared four trap types and determined temperature-based phenology of this pest over two growing seasons. Large delta traps captured the greatest number of male moths, and similar moth captures were found with or without monthly lure changing. Traps placed at field perimeters adjacent to woods trapped significantly more moths than those inside fields, whereas position in the canopy (high versus low) did not affect captures. Under laboratory conditions, the lower developmental threshold for larvae was 12.3 degrees C, in close agreement with field studies indicating a 12.8 degrees C threshold. Using the 12.8 degrees C threshold, monitoring of O. leucostigma cohorts on caged blueberry plants revealed a spring generation with egg hatch starting at 206 +/- 3 growing degree-days (GDD) and a late-summer generation with egg hatch starting at 1,157 +/- 52 GDD. Combined use of optimized monitoring methods and the phenology model for O. leucostigma is expected to improve integrated management of this pest in blueberry.