Search

AbstractAdelges tsugaeAnnand (Hemiptera: Adelgidae), a nonindigenous insect pest of hemlock (Tsugaspp.) (Pinaceae) in eastern North America, spends most of its life cycle within an ovisac, which resembles a woolly white mass on twigs. We evaluated the probability of detecting adelgid wool with Velcro®-covered balls when taking an increasing number of samples per tree (field sampling) and number of trees per simulated stand. We examined the relationship between the detection of adelgid wool using this technique and the incidence of A. tsugae-infested twigs by sampling lower-crown branch tips of the same trees. We found that the probability of detecting wool with ball sampling increased with number of ball samples per tree, with number of trees per simulated stand, and with increasing incidence of ovisacs in the lower crown. When sampling an individual tree, we found that 20 ball samples per tree achieved a targeted precision level of 0.75, but when sampling a stand, we found that 10 ball samples per tree took the least time for the range of simulated A. tsugaeinfestations we tested. These sample sizes are recommended for detection of A. tsugaeinfestations on an individual tree and in a hemlock stand.

AbstractAdelges tsugaeAnnand (Hemiptera: Adelgidae) has caused extensive mortality of hemlocks (Tsuga(Endlicher) Carrière; Pinaceae) in the eastern United States of America and was discovered recently in Nova Scotia, Canada. We evaluated the use of a Velcro-covered racquetball as a sampling device for A. tsugaewool. Specifically, we report on improvements to an earlier design and evaluate several factors seen in routine sampling that influence the ability of the ball to trap and retain adelgid wool. Velcro was found to be critical for trapping and retaining adelgid wool on the ball during flight and landing. Wooden beads, inserted in the ball, reduced deflection during flight and bounce during landing. Higher probability of trapping wool on the ball was associated with an ascent through the crown, with increasing diameter and density of ovisacs on branch tips, and with increasing abundance of woolly twigs on the forest floor. Higher probability of retaining wool on the ball was associated with Velcro surface area and with amount and location of wool loaded on the ball. These modifications improved detection surveys for A. tsugaein general.

AbstractDiscovery of the non-native Anoplophora glabripennisMotschulsky (Coleoptera: Cerambycidae) in Ontario, Canada, in 2003 led to the implementation of an eradication programme. The plan consisted of removing all infested trees and all trees belonging to a genus considered suitable for complete development of this wood-borer that were found within 400 m of an infested tree; however, many of the trees within that 400 m belonged to genera for which suitability for development of A. glabripenniswas questionable or unknown. We visually inspected over 3000 such trees annually for the three years following removal of infested trees. All but one tree were unattacked: an ash (Fraxinus excelsiorLinnaeus (Oleaceae)) tree had signs of oviposition and early-instar development, but not of adult emergence. Before that survey, we had found only one other species with questionable suitability, a little leaf linden (Tilia cordata Miller (Malvaceae)) that had many signs of oviposition, but no evidence of full development, suggesting resistance to A. glabripennis. Both of these trees were within 200 m of the most heavily infested maple (Acer platanoidesLinnaeus (Sapindaceae)) tree found in that infestation, suggesting that colonisation of trees with questionable or unknown suitability might occur mostly where population pressure is high.

AbstractAgrilus planipennis(Coleoptera: Buprestidae), is causing extensive mortality of ash (FraxinusLinnaeus; Oleaceae) in North America. Once detected in an area, resource managers require methods to obtain estimates that could improve management decisions. We studied the within-crown and within-branch distribution and abundance of A. planipennisfeeding galleries by sampling 3-m-long branches from asymptomatic urban ash trees and subdividing each branch into 12 sections of 25 cm each. We found galleries in all 12 sections of some, but not all, branches. Section was a significant source of variation in A. planipennisgallery density/m2of branch surface area. A comparison of predictive power and efficiency of estimates for samples of increasing length, and for samples of the same length but consisting of different combinations of sections, revealed that those based on the two basal 25-cm sections of a branch from the lower-crown or mid-crown of an asymptomatic tree were less accurate and precise than those based on more sections, but were the most cost effective. Whittling more sections per branch, irrespective of the combinations of branch sections per length, improved predictive power but reduced cost effectiveness. We also observed that crown level was not important, and aspect was only marginally so, when estimating gallery abundance per sampled branch.

AbstractDetection of the exotic hemlock woolly adelgid, Adelges tsugaeAnnand (Hemiptera: Adelgidae), in the crown of eastern hemlock, Tsuga canadensis(Linnaeus) Carrière (Pinaceae), relies mainly on two techniques: (1) sampling of branches from the lower half of the crown using pole pruners; and, (2) visual examinations of accessible foliage from the ground. As a result, infestations starting elsewhere than the lower crown may be missed because the upper crown is out of reach for both techniques. We developed a novel technique called ball sampling, and evaluated its sensitivity at detecting a range of A. tsugaeovisac densities as estimated by pole pruning branch tips of T. canadensis. We launched racquet balls covered with VELCRO®patches of hooks through branches and examined them for the presence of wool produced by A. tsugae.Ball sampling was as effective as pole pruning at detecting infestations in individual trees. If A. tsugaeabundance on branches was ?0.1 per 10 cm of twig length, as estimated by branch-tip sampling, ball sampling always detected wool in 10 or fewer samples. This technique has the potential to improve detectability of A. tsugaeinfestations because it can effectively access foliage that is typically inaccessible to other ground-based detection tools.

AbstractIntroductions of some forest invasive alien species result in important economic, environmental, and ecological impacts. One approach used by the Canadian Food Inspection Agency to improve the detection of these species is to collect logs from trees in declining health at high risk sites of introduction and to incubate them to obtain insects, if present. Trichoferus campestris(Faldermann) (Coleoptera: Cerambycidae) adults emerged, and live larvae were extracted, from one of two logs taken from a dying Norway maple, Acer platanoidesLinnaeus (Sapindaceae), in Mississauga, Ontario, Canada. In its native range, eastern Asia, this beetle is polyphagous, however, in North America there is no host record despite numerous interceptions of larvae in wood packaging material and captures of adults at various post-entry sites. An examination of the feeding damage caused by T. campestrisin that maple suggests this insect is not a primary pest of trees in Ontario.

AbstractAn established population of the exotic woodwasp Sirex noctilioFabricius (Hymenoptera: Siricidae) was first detected in North America in 2004. In order to develop survey guidelines for the detection of this major pest of PinusLinnaeus species in the Southern Hemisphere, we examined 231 Pinus sylvestrisbiweekly to establish the timing and spatial distribution of resinosis symptoms of attack, and the timing of subsequent tree mortality. Fresh resin appeared between mid-July and late August, and on 70% of infested trees was observed on the mid bole. The occurrence of tree death varied between sites, from 2 weeks after the first detection of resinosis in one site to several months in seven other sites. Findings from our study provide key information to improve detection of S. noctilioand predict its impact on forest stands in its new range in northeastern North America.

AbstractA 2-year field study was carried out to locate and identify eggs, determine the temporal distributions of eggs and larvae, and assess the impact of Strobilomyia laricisand S. viariaon Larix laricina. Eggs of S. lariciswere beige with a patterned surface and usually laid one per cone in the bud scales at the base of the cone. Eggs of S. viariawere white and smooth and usually laid one per cone between the ovuliferous scales of the cone. Strobilomyia laricisoviposited from mid- to late May and S. viariafrom late May to mid-June, each species initiating oviposition at a different stage of cone phenology. Peak egg densities of S. lariciswere 25 and 65% higher than those of S. viariain 1990 and 1991, respectively. Larvae of both species completed development at the same time, from mid-June to early July. The mean number of scales eaten per cone did not differ between species; one larva damaged a mean of 8.4 scales per cone in 1990 and 10.7 scales per cone in 1991. As the number of scales per cone increased, the mean number of scales eaten increased and the mean percentage of scales eaten decreased. Cone crops were light in both years. In 1990, the only year we were able to differentiate cone maggot larvae, 44% of cones were damaged by S. laricisand only 16% by S. viaria. Together, S. laricisand S. viariadamaged 60 and 67% of the cones and destroyed 38 and 50% of the potential seed crop in 1990 and 1991, respectively.

AbstractThe life cycle of Strobilomyia appalachensisMichelsen, a maggot exploiting black spruce seed cones, was studied in two plantations in northern Ontario in 1987 and 1988, and two seed orchards in New Brunswick in 1991 and 1992. Oviposition by S. appalachensisoccurs slightly later than the white spruce cone maggot, S. neanthracinaMichelsen, relative to seed cone development; otherwise the life cycles of the two species are similar. Adults were trapped near host foliage in May and early June. Eggs were laid between the scales of seed cones during early June, starting when the scales on most cones were closed and ending 1 week after cones were fully pendant. Up to five eggs per cone were observed but single eggs were most common. The first larval molt occurred within the egg chorion and second-instar larvae emerged from the egg. Second-instar larvae were found in the cones during the 2nd and 3rd week of June, and third instars from the 3rd week of June until mid to late July. Larvae tunneled around the cone axis and destroyed an average of 60% of the total seed per cone before exiting and dropping to the soil. Larval drop occurred from late June to late July and was significantly correlated with periods of rainfall. Mature larvae moved into the duff and overwintered in the soil as pupae. Aspects of the maggot’s life history are discussed in relation to pest management strategies.

AbstractTwo species of cone maggots, StrobilomyiaMichelsen, are known to attack seed cones of spruces in North America. Seed cones of black, red, and white spruce from Newfoundland to Alberta were collected to determine the number of host species and the distribution of these maggots. Strobilomyia appalachensisMichelsen was obtained only from seed cones of black and red spruce, whereas S. neanthracinaMichelsen was obtained only from white spruce seed cones. Our observations represent the first record of S. appalachensisin Canada. We conclude that, like S. neanthracina, S. appalachensishas a transcontinental distribution, but exploits different hosts, namely black and red spruce. We also observed that S. appalachensiswas capable of extended diapause.

AbstractThe age at which Pseudaletia unipunctafemales initiated calling varied with temperatures experienced during pupal and adult stages. Entrainment was induced by temperatures during pupal development if similar to or lower than temperatures during adult life. However, adult temperatures were of major importance if lower than those experienced during pupal development. These observations were generally supported by data from field experiments repeated at different periods of the summer. The possibility that entrainment occurs at a specific period of development is proposed to explain certain field observations.Changes in mean onset time of calling and the time spent calling also varied, although generally not in the same manner as reported for other species. Differences in the life cycles, particularly the site of pupation, are proposed to explain these discrepancies.

AbstractThe spatial and statistical distribution of Zeiraphera canadensisMut. and Free. (spruce budmoth) within the crown of white spruce (< 4 m high) was investigated in northern New Brunswick. A 15-cm branch segment, measured distally from the scales of the branch’s apical growth and taken from the upper one-third of the crown, is considered an adequate sample unit for density estimates of spruce budmoth eggs and larvae. Sample sizes required to estimate spruce budmoth larval densities with given levels of precision and confidence were determined. A sequential sampling plan to classify spruce budmoth populations as low or high (potentially leading to growth reduction and deformed leaders in white spruce) was also developed.

AbstractThe relationship between the phenological development of the spruce budmoth (SBM), Zeiraphera canadensis, and that of its primary host, white spruce, was studied in New Brunswick using descriptive indices for both insect and host development. Larval emergence of SBM was synchronized with bud burst of white spruce, the species on which most eggs are laid. Subsequent SBM larval development can be estimated through reference to the development index for white spruce. For black, Norway, and red spruce, initial bud burst occurred approximately 15, 3, and 15 days, respectively, later than white spruce and this asynchrony is probably one of the reasons why the SBM is not an important pest on these tree species.

AbstractThe life cycle, feeding behavior, and feeding damage of the spruce budmoth, Zeiraphera canadensis, were studied in northern New Brunswick. Larval emergence, which began in late May, was usually completed within 10 days. First-instar larvae did not feed on the previous year's foliage and took less than 30 min to settle inside a growing shoot, from which they exited only at the end of larval development. Larvae then dropped to the ground and remained as prepupae for approximately 6 days. Mating could be observed the first night following adult emergence. The majority of the mated females contained only 1 spermatophore (92%); others had 2 (7%) or 3 (1%). Although 95% of the egg clusters had 7 eggs or less, 5% had up to 19 eggs. Eggs required embryonic development before successful diapause could be initiated. The importance of these observations in the development of management strategies for this pest is discussed.