Annual counts of larvae of western spruce bud worm, Choristoneura occidentolis Free., from beating samples of Douglas-fir (Pseudotsuga menziesii Mirb.) Franco) were analyzed over 30 years. Sampling points which most frequently yielded high budworm counts and also had detectable defoliation were analyzed and compared with results from all the samples. When the purpose of sampling was to predict populations, the 98 points sampled since 1949 could be reduced to 17, thus enabling a significant reduction in the cost of data collection.

Methods of separating Pissodes strobi (Peck) from its insect associates in leaders of Picea sitchensis (Bong.) Carr. would enable the associates to be returned to the field when infested leaders are routinely clipped to remove P. strobi. We recently demonstrated a method based on the relative lack of cold-hardiness of P. strobi (Hulme et al. 1986). Another method suggested many years ago (e.g. Taylor 1929) is to exploit the different ability of adult insects to crawl through a screen. To our knowledge the efficacy of such a separation has never been demonstrated. We report here an investigation into the ability of these adult insects to crawl through screens having openings of various sizes, with the objective of establishing how completely these insect associates could be separated from P. strobi

AbstractThe cold-hardiness ofPissodes strobi(Peck) and of its insect associates in leaders ofPicea sitchensis(Bong.) Carr. was tested to determine whether the insect associates could be retrieved free ofP.strobifor use in biological control attempts onP.strobi. Leaders were stored at −8, −16, or −26°C for periods from 1 to 14 days. AllP.strobiwere dead after 14 days at −16°C, whereas their dipteran predator,Lonchaea corticisTaylor, and hymenopteran parasites,Eurytoma pissodisGirault andRhopalicus pulchripennis(Crawford), continued development after storage at −26°C. The scarcerDolichomitus terebrans(Ratzeburg) (Ichneumonidae) survived similarly although we did not always find it in our samples; and the equally scarceBracon pini(Muesebeck) (Braconidae) seemed susceptible to −26°C but continued development at −16°C. Of the fewAllodorus crassigaster(Provancher) (Braconidae) obtained one adult emerged after 7 days at −16°C. These results show that in leader clipping operations now used for attempted control ofP.strobi, most of the insect associates could be retrieved from the leaders after suitable cold treatment. Additional tests showed that cold-treated leaders could be stored outdoors in temperatures at least down to −20°C with little effect on adult emergence of insect associates. The field testing also showed that fewP.strobiin leaders ofP.sitchensiscan survive overnight temperatures near −20°C.

Insects associated with the Sitka spruce weevil, (Peck), on Sitka spruce, (Bong.) Carr. were sampled at 9 locations in British Columbia. Fourteen species of hymenoptera, 3 diptera, and 1 psocopteran were found associated with the weevil. Samples were dominated by the lonchaeid predator, Taylor, and to a lesser extent by the braconid parasitoid, (Prov.).Des récoltes d'insectes associés au charançon du pin blanc ( [Peck]) sur l'épinette de Sitka ( [Bong.] Carr.) ont été réalisés dans 9 localités de Colombie Britannique. Quatorze espèces d'hyménoptères, 3 de diptères et 1 de psocoptère ont été retrouvées associées au charançon au cours de ces récoltes. Le prédateur de la famille des Lonchaeidés, Taylor dominait, suivi du parasitoide de la famille des Braconides: (Prov.).

Insects associated with the Sitka spruce weevil,Pissodes strobi (Peck), on Sitka spruce,Picea sitchensis (Bong.) Carr. were sampled at 9 locations in British Columbia. Fourteen species of hymenoptera, 3 diptera, and 1 psocopteran were found associated with the weevil. Samples were dominated by the lonchaeid predator,Lonchaea corticis Taylor, and to a lesser extent by the braconid parasitoid,Allodorus crassigaster (Prov.).

AbstractThe relationship of western spruce budworm outbreaks and population collapse to weather parameters was examined using long term weather records from two stations in the budworm outbreak area of British Columbia and outbreak patterns obtained from Forest Insect and Disease Survey records and from tree stem analyses.Outbreaks were associated with warm dry summers in conjunction with synchrony of larval emergence and bud flush. Collapse of the last two outbreaks was clearly associated with extreme high temperatures following moth flight. Collapse of the earlier outbreaks may have been due to asynchrony between larval emergence and bud flush.

AbstractA simple empirical model of temperature variation with elevation was successfully used to explain variation in observed rates of development of larvae and pupae of the western spruce budworm in mountainous terrain. Hopkins' Bioclimatic Law did not adequately describe development of stages earlier than the sixth instar. Regional differences in the effect of elevation are demonstrated and related to coastal and interior conditions. Direct solar heating effects appear to be of major significance in the early instars. The empirically-derived rates of temperature decrease could be generally applied to regions with dry inland conditions, but not to moist coastal regions.

Western spruce budworm, Choristoneura occidentalis Freeman, periodically attacks Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco) in British Columbia, causing mortality, deformity, and growth loss. Insect populations are assessed annually by the Canadian Forestry Service's Forest Insect and Disease Survey, by branch sampling for egg mass densities; predictions of population trends and damage are based on these assessments. Eggs, laid in rows in masses affixed to needles, are a preferred stage to sample because they are easily collected, remain fixed in numbers for an extended period, and precede damage by sufficient time to plan suppression or other programs. Numbers of masses alone, however, may not show population trends accurately as egg numbers per mass varies. Thus it is sometimes necessary to count eggs (Miller 1957), which is a formidable task. Fortunately egg numbers can be estimated from the dimensions of egg masses (Washburn and Brickell 1973). In this study, we determined the relationship between egg numbers and egg mass length and number of rows for samples from Douglas-fir stands frequently affected by spruce budworm throughout British Columbia. Data were collected over 3 years, 1977-79, during which time budworm populations were in a period of decline.

AbstractA procedure for sampling defoliating forest insect larvae by beating them from foliage, used by the Forest Insect and Disease Survey of the Canadian Forestry Service to record population trends and predict future damage and control need in British Columbia, was tested over 150,000 acres on Vancouver Island. The parameters used were average numbers of larvae per collection and percentage positive collections. Results on the test species Acleris gloverana (Wlshm.) and Melanolophia imitata (Wlk.), on host Tsuga heterophylla (Raf.) Sarg., indicated that for low (normal) population levels the present system of choosing three-tree samples along roadsides was satisfactory but that weather conditions markedly affected sample results.

AbstractA study was made of the poplar-and-willow borer, Sternochetus (= Cryptorhynchus) lapathi (L.) (Coleoptera: Curculionidae), in British Columbia between 1959 and 1964. The borer occurred principally south of 52 degrees north latitude. Willows were the preferred hosts. Ornamentals, hybrids in commercial plantings, and natural growing trees were attacked. The life cycle of the insect on southern Vancouver Island lasted up to 3 years; overwintering took place in early instar and adult stages. Eggs were laid in the bark; larvae mined first in the bark and then in the wood, where pupation took place. Few parasites and predators were found. DDT, dieldrin, and BHC killed adults; lindane (0.5% water emulsion), applied in the spring, caused larval mortality up to 96%.