Search

Garry oak, Quercus garryana Douglas ex Hooker (Fagaceae), is part of a unique ecosystem in British Columbia, Canada, which is rich in rare and endangered plant species. Garry oak recruitment is critical to the existence of this ecosystem, therefore, the effect of Curculio occidentis (Casey) (filbert weevil; Coleoptera: Curculionidae) and Cydia latiferreana (Walsingham) (filbertworm; Lepidoptera: Tortricidae) on acorn germination is of great interest. Together these two insects infested 80.7%, 75.1%, and 51.3% of acorns collected in 1996, 1997 (low crop years), and 1998 (high crop year), respectively. Filbertworm infestation did not vary with crown level. Filbert weevil infestation did not vary with crown level during poor crop years, but significantly more filbert weevil-infested acorns were found in the lower than the middle and upper portions of the trees during the high crop year. Severely damaged acorns did not germinate, and acorns with light to moderate feeding damage had lower germination success than undamaged acorns, but growth of germinated seedlings in the light to moderate damage category was unaffected. This study showed, for the first time, that these two insect species infested a large proportion of Garry oak acorns on the tree in British Columbia, and that light to moderate damage of the acorn has relatively low impact on seedling growth.

We studied Orgyia pseudotsugata multiple nucleopolyhedrovirus (OpMNPV) infections in larvae of the Douglas-fir tussock moth, Orgyia pseudotsugata McDunnough (Lepidoptera: Lymantriidae), to determine the quantity of OpMNPV particles that result in mortality. We observed a bimodal pattern of mortality in Douglas-fir tussock moth larvae that ingested diet plugs contaminated with 9.5 OpMNPV occlusion bodies. A mortality peak (80% of total mortality observed) occurred between day 5 and day 11 post ingestion, and a second, smaller mortality peak coincided with the onset of pupation. Virus loads, defined as the number of OpMNPV occlusion bodies in each sample of tested larval homogenate, were quantified using an indirect ELISA method. Virus loads that resulted in mortality were significantly greater than those quantified in larvae that were sacrificed during and after the peak mortality wave (P < 0.004 and P < 0.0001, Mann–Whitney U two-tailed rank test and SPSS®, respectively). This is the first known attempt to differentiate the quantity of virus produced during lethal infections from the virus loads in larvae that survive infection.

Field trapping trials showed that Cameraria gaultheriella Walsingham and C. lobatiella Opler and Davis (Lepidoptera: Gracillariidae) were attracted in significant numbers in British Columbia, Canada, to sticky traps baited with 10 µg of (E,Z)-8,10-tetradecadienal (E8Z10-14Ald), the sex pheromone of the European horse chestnut leafminer, C. ohridella Deschka and Dimic. There was perfect specificity in captures at habitats located only about 8 km apart from each other: C. gaultheriella was captured exclusively at a humid habitat covered by the shrub salal, Gaultheria shallon Pursh (Ericaceae), whereas C. lobatiella was trapped at an arid location with Garry oak trees, Quercus garryana Dougl. (Fagaceae). Seasonal flight patterns of these two Canadian Cameraria species, as monitored by pheromone traps, indicated differences in their respective flight periods. The possibility of additional cryptic components in the respective pheromones of these three Cameraria species attracted to E8Z10-14Ald is discussed.

Two newly identified geographic isolates of a nucleopolyhedrovirus (LdMNPV-H and LdMNPV-J) were evaluated against Disparvirus (LdMNPV-D), a baculovirus insecticide registered in Canada for the control of gypsy moth (Lymantria dispar (L.) (Lepidoptera: Lymantriidae)). Profiles of HindIII and EcoRI restriction enzyme digests of viral DNA from the three viral isolates are presented. Viral isolates were bioassayed using an inoculated diet plug method to determine the dose- and time-responses of second-instar larvae of both the European and Asian strains of gypsy moth. LdMNPV-D was found to be the most virulent isolate when tested against the European strain of gypsy moth, yielding an LD50 and an LD95 (estimates of the doses required to kill 50% and 95% of the test larvae, respectively) of 95 and 774 occlusion bodies (OBs), respectively. LdMNPV-H was the most virulent isolate when tested against the Asian strain, yielding an LD50 and an LD95 of 648 and 8540 OBs, respectively. Time-response data indicate that the three isolates differ little with respect to their speed of kill (ST50; estimate of the length of time required to kill 50% of the test insects) of either larval strain. These results indicate that both new isolates (LdMNPV-H and LdMNPV-J) should be investigated further for control of the Asian strain of the gypsy moth but not pursued for control of the European strain.

Optical brighteners were recently discovered to function as UV protectants for baculoviruses of insects (Shapiro 1992) and, also, to enhance entomopathogenic activity of these viruses (Hamm and Shapiro 1992; Li and Otvos 1999a). Enhancement of viral activity by brighteners varied greatly from one virus–host system to another: for example, from 1500-fold in LdMNPV against Lymantria dispar (L.) (Lepidoptera: Lymantriidae) (Argauer and Shapiro 1997) to 2- to 13-fold in a multicapsid nuclear polyhedrosis virus of Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae) (CfMNPV) against Choristoneura occidentalis Freeman (Li and Otvos 1999a). The reason for this variation in enhancement of viral activity is still unknown. In this study, we used CfMNPV to compare the levels of viral enhancement by an optical brightener between C. occidentalis and C. fumiferana.

The hemlock looper, Lambdina fiscellaria (Gn.), is a recurring major forest pest that is widely distributed in North America. Three subspecies (L. f. fiscellaria, L. f. lugubrosa (Hulst) and L. f. somniaria (Hulst)) have been recognized based on larval host or adult pheromone differences, but no consistent morphological differences have been reported. To clarify their taxonomic status, we surveyed mitochondrial DNA (mtDNA) sequence and restriction site variation in two protein coding genes, cytochrome oxidase I and II (COI and COII), in populations across the range of L. fiscellaria. In addition to variation in COI and COII, we found an intergenic spacer region of 20-23 bp located between the tRNA tyrosine gene and the start of COI. Of the 141 specimens of L. fiscellaria assayed, 137 were grouped into two distinct mtDNA lineages, one of which was disproportionately associated with eastern populations and one with western populations. However, single specimens and two populations in eastern Canada had mtDNA resembling that of western populations. Three divergent and rare haplotypes had basal affinities to the two common lineages. The two major lineages of L. fiscellaria were diverged by approximately 2% from each other, as well as from the mtDNA of two outgroup species, L. athasaria (Walker) and L. pellucidaria(G. & R.). The two outgroup species had essentially the same mtDNA and may be conspecific. We interpret the pattern of mtDNA variation within L. fiscellaria as indicating genetic polymorphism within a single species without clear subspecific divisions, rather than evidence of multiple cryptic species.

Fifth-instar larval mortality was compared between male and female Choristoneura occidentalis Freeman exposed in the laboratory to sublethal doses of Choristoneura fumiferana (Clem.) multicapsid nuclear polyhedrosis virus (CfMNPV) with or without optical brighteners. More females than males died when the virus was used alone, but differences were not significant. When 1% brightener was added to CfMNPV suspension, differences in larval mortality between males and females were significant for three of the four brighteners tested. In addition, times at which 50% of the larvae died indicated that female larvae died 23 and 39% more quickly than male larvae, respectively, when brightener Blankophor HRS and Tinopal LPW were added to the virus, whereas at times at which 95% of the larvae died indicated that females died 33 and 54% faster than males. Alteration of sex ratio favoring male survival can play a significant role in the biological control of C. occidentalis by the virus.

Erannis tiliaria Harr. and Erannis defoliaria Cl. are closely related species (Rindge 1975) that have similar external appearance and flight period. Erannis tiliaria occurs in North America, whereas E. defoliaria is confined to Europe. Erannis defoliaria occasionally damages oak, Quercus spp. L. (Fagaceae), and cheny, Prunus spp. L. (Rosaceae) (Reichart 1993). During its 1975 outbreak, E. tiliaria severely defoliated 200 000 ha of white and yellow birch, Betula alleghaniensis Britt. and Betula papyrifera Marsh. (Betulaceae), respectively (Howse et al. 1995).

Infections of two heterologous insect cell lines derived from Malacosoma disstria (Md108) and Choristoneura fumiferana (Cf70) by the Lambdina fiscellaria lugubrosa nucleopolyhedrovirus (LafiNPV-W) were characterized. Cytopathic effects characteristic of LafiNPV-W infection, including rounding of cells, nuclear hypertrophy, and occlusion body (OB) production, were observed in both cell lines. Budded virus titers were slightly higher in Md108 cells than Cf70 cells (5.8 x 10(7) versus 3.1 x 10(7) TCID(50) units mL(-1)). Viral replication kinetics and cytopathic effects induced by LafiNPV-W infection were very similar in both cell lines. Actin rearrangements and redistribution of heterochromatin and euchromatin were observed within 24 h post-inoculation (hpi), and large quantities of nucleocapsids and virions were observed by electron microscopy at 48 hpi in both cell lines. Cf70 cultures produced OBs with numerous embedded virions, while OBs in Md108 cultures contained few virions or were empty with nucleocapsids packed in the nucleoplasm between OBs. In bioassays against second instar L. fiscellaria lugubrosa, OBs derived from LafiNPV-W-infected Md108 cells induced significantly lower levels of mortality than OBs derived from LafiNPV-W-infected Cf70 cells or from infected L. fiscellaria fiscellaria larvae.

Orgyia pseudotsugata multicapsid nucleopolyhedrovirus (OpMNPV) DNA was extracted from samples representing 10 lots of TM Biocontrol-1 stored at -10 degrees C for 5-15 years and digested with the restriction enzymes BglII, PstI, and SalI. DNA from the OpMNPV virus strain (MEM-75-STANDARD) used to produce the TM Biocontrol-1 lots was also extracted and digested. No restriction fragment length polymorphisms were observed in any of the samples and there was no evidence of DNA degradation. This indicates that long-term cold storage of TM Biocontrol-1 had no adverse effect on the quality of the OpMNPV DNA. In addition to the expected >23 kb OpMNPV DNA, extracts from lots 4a, 5b, and 6 contained 10 additional nucleic acid segments, ranging in size from 0.9 to 4.2 kb. The electrophoretic profile of these segments was characteristic of O. pseudotsugata cypovirus (OpCPV). RNase A/DNase I treatment showed that the nucleic acid contaminants were composed of RNA, suggesting that lots 4a, 5b, and 6 contained OpCPV as well as OpMNPV. Bioassay results have shown that there is a decrease in efficacy of stored TM-biocontrol-1, but this did not appear to be directly correlated with the length of time in storage.

Two viruses, one a nuclear polyhedrosis virus and the other a granulosis virus, were applied in an attempt to initiate epizootics in populations of western spruce budworm, Choristoneura occidentalis Freeman, on Douglas-fir trees, Pseudotsuga menziesii (Mirb.) Franco, in southeastern British Columbia. Two 172-ha plots were aerially treated in 1982 with 9.0 kg of lyophilized, virus-infected larval powder that was formulated in an emulsifiable oil tank mix and applied at 9.4 L per hectare. Each plot was treated when larval populations were at the peak of the fourth instar. The nuclear polyhedrosis virus was applied at 5.4 × 1011 polyhedral inclusion bodies per hectare and the granulosis virus at 1.7 × 1014 capsules per hectare. Results showed that the granulosis virus treatment caused 34.6% population reduction (Abbott’s formula) and the nuclear polyhedrosis virus 51.8%. Larvae from treated and check plots were reared individually in the laboratory and the incidence of viruses, parasitoids, and successful adult emergence was recorded. Studies m these plots continued in 1983 and 1984. Although vertical transmission of both viruses was evident, their impact on budworm mortality was less than in 1982. Consequently, the epizootics were not sufficiently intense to control the target insect population.

Two different application methods were tested using a nuclear polyhedrosis virus as a control agent at an early stage in the outbreak cycle of Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), in south central British Columbia in 1981. The virus, which often leads to the development of an epizootic late in the outbreak cycle, was propagated in whitemarked tussock moth, Orgyia leucostigma (J. E. Smith). A helicopter fitted with a boom and nozzle was used for treating four plots (total area 19.8 ha) at a dosage of 2.2 × 1011 polyhedral inclusion bodies (PIB) in an emitted volume of 11.3 L ha−1. Five to eight weeks after spraying, microscopic examination of live larvae showed that 77 to 100% were infected. In ground-spray applications of two other plots, a modified orchard-type sprayer was used to apply 2.4 × 1010 PIB in a volume of 4.5 L per tree. Microscopic diagnosis of live larvae at 8 weeks post-spray revealed 83 and 85% infection.In autumn 1981, no egg masses could be found in the plots treated earlier that year and no larvae were found on the sample trees in 1982 or 1983. The treatment was effective over a range of initial mean larval densities of 41 to 206 m−2 of foliage. At the same time, populations in nearby untreated areas increased in 1982. Little foliage protection was obtained the year of application due to the lengthy virus incubation period, but the trees recovered quickly when populations disappeared due to the virus epizootic.

Several host–parasitoid models were examined to assess the feasibility of parasitoid inundation as a means of pest control or eradication. The approach is comparative, to assess independently the effects of various ecological factors on the ease of control by this means. For most of the models, there exists a critical inundation rate, I*, above which the host population is eradicated, provided inundative releases continue beyond the time of eradication. The existence of density-dependent mortality in the hosts reduces the time to eradication but does not affect I*. Density dependence in the parasitoids, however, usually increases I*. The existence of hyperparasitoids appears to have no effect on the ease of host eradication.

A 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.

The diets of 25 species of forest-inhabiting birds were examined in California from 1962 to 1968. Coleoptera and Hymenoptera comprised the bulk of the diets. Coleopterans were, in decreasing amounts, the most common food of the three-toed woodpecker, Steller's jay, American robin, brown creeper, hairy woodpecker (both sexes), dark-eyed junco, downy woodpecker (both sexes), olive-sided flycatcher, western wood-pewee, and white-headed woodpecker (both sexes). Hymenopterans, mainly ants, were the most common food of the northern flicker, Williamson's sapsucker, red-breasted sapsucker, and acorn woodpecker. White-headed woodpecker (both sexes) also ate ponderosa-pine seeds in the fall. Hairy woodpecker (both sexes) fed on the seeds of ponderosa pine and sugar pine. Detailed estimates of foods consumed by item and volume from analyses of stomach contents of 241 specimens are presented.

Four 10-ha plots located in Kamloops Forest District, British Columbia, containing Douglas-fir trees infested with Douglas-fir tussock moth were aerially sprayed with nuclear polyhedrosis virus (Virtuss) in 1982 when most larvae were in the first instar. A dosage of 2.5 × 1011 polyhedral inclusion bodies (PIB) per hectare was applied in an emulsifiable oil tank mix to one plot and the same dosage in an aqueous tank mix containing molasses was applied to a second plot. The remaining two plots were treated with dosages of 8.3 × 1010 and 1.6 × 1010 PIB per hectare, respectively, in the oil mix. The treatments were applied with a fixed-wing aircraft fitted with boom and nozzle equipment and calibrated to deliver 9.4 L/ha. A further four plots were selected as checks.Population reduction at 6 weeks post-spray (calculated using a modified Abbott’s formula) was 65% in the plot receiving the lowest dosage and from 87 to 95% in the remaining three plots. Incidence of virus infection, determined microscopically, peaked at 5–6 weeks post-spray with 85–100% of the larvae scored as positive. Levels of naturally occurring virus remained low in the check plots. Adult emergence from the pupae collected in the treated plots ranged from 4 to 19% and from 28 to 43% in the check plots. Reduction in egg-mass density attributed to the treatments was 97% in one plot, 99% in two others, and not determined for the fourth.A virus dosage of 8.3 × 1010 PIB per hectare, which is one-third of the previously recommended dosage, is adequate, and either tank mix is acceptable.

Four species of woodpeckers (family Picidae) are definitely known to be predaceous on the western pine beetle in the Central Sierra Nevada Mountains in California. These are: Dendrocopus villosus, Dendrocopus pubescens, Dendrocopus albolarvatus and Dryocopus pileatus. The red-shafter flicker (Colaptes cafer, Picidae), creepers (Certhiidae), nuthatches (Sittidae), and flycatchers (Tyrannidae) are thought to be predators on the western pine beetle.Predation by woodpeckers reduced the western pine beetle population by (a) actual consumption of 31.8% in two generations studied, and (b) by increasing parasite densities in the order of 3.85 factor. The increase in parasite density was believed to have been caused by bark removal to a near uniform thickness enabling a higher parasitism by those parasites with short ovipositors, such as Cecidostiba and Roptrocerus spp.One adverse effect of woodpecker predation was a reduction or a depression of insect predation. Highly mobile insect predators may have been driven away by woodpecker activity, actually consumed, or both.Bark flakes, chipped or pried off by the woodpeckers during their feeding activity, contained but few insects and it is doubtful that these could survive on the ground and reach the adult stage.

Western false hemlock looper, Nepytia freemani Munroe, is a cyclical pest in British Columbia which defoliates mainly Douglas-fir, Pseudotsugata menziesii (Mirb.) Franco, often near residential areas. Outbreaks were recorded from 1947 to 1949, 1963 to 1964, and 1972 to 1976; the current outbreak started in 1980 and, in 1982, covered 1,100 ha near Tappen, Canoe, Enderby, and Carquile (Ferris and Woensdregt 1983).

Three types of traps were tested in 1969 and 1970 for collecting pupae of the eastern hemlock looper, Lambdina fiscellaria fiscellaria (Guen.). Highest numbers of pupae were obtained with burlap traps made from 2-ft-wide bands wrapped around trunks of infested trees. The proportion of the pupae in the burlap traps was estimated. Some of the potential uses for pupae collected by the method are mentioned.

Winthemia occidentis Rhn. was introduced into Newfoundland to strengthen the parasite complex of the eastern hemlock looper. This tachinid has two emergence periods, one in the fall, the other in the following spring. A method was developed for rearing overwintering tachinid larvae to the adult stage. The best rearing results were obtained when the larvae were stored outdoors in jars of peat moss for the fall and winter period and removed to controlled temperature and humidity conditions in the spring, to complete development.