During a severe outbreak of spruce budworm, Choristoneura fumiferana (Clem.), some balsam fir trees, Abies balsamea (L.) Mill., remain noticeably greener than others in the same stand. We show that this ‘green’ tree phenomenon is not caused by differential defoliation in which certain trees experience consistently low defoliation pressure throughout an outbreak. Rather, these trees remain ‘green’ because of their prolific, epicormic shoot production which is consistently high during an outbreak, giving them a ‘greener’ appearance than other trees that produce lower numbers of epicormic shoots.

Requirements for diapause development of larvae of Choristoneura fumiferana have been generally believed to be met by temperatures of 2°C or below for a period ranging from 14 to 20 weeks (see review by Sanders 1991), whereas those favourable for post-diapause development were shown to be above 11°C (Régnière 1990). However, we noticed that a large number of larvae completed diapause after 10 weeks at 18°C without any cold storage. The following experiment was carried out to confirm this result.

While conducting research on the geographic origin of the wheat stem sawfly (Cephus cinctus Norton), we compared North American specimens to specimens of Eurasian Cephus spp., and discovered that specimens currently placed as C. hyalinatus Konow from Siberia are conspecific with the North American species. Given the pest status of the North American populations, which attack wheat and other cereals in the upper Great Plains (Weiss and Morrill 1992), this discovery has important implications for the management of the species. Discussion of these implications will be provided elsewhere (Ivie 1996).

The addition of legumes in the small grain cropping system of the western prairie regions of North America has several advantages: an increased diversity in the landscape may reduce pest loads of insects, plant pathogens, and weeds; a decreased financial risk for producers by diversifying the types of crops produced; and increased soil nitrogen via fixation and mineralization. Several alternative legumes are being examined for potential production in this region, including lupins (Lupinus spp.), faba bean (Vicia faba L.), chickpea (Cicer arietinum L.), and lentil (Lens culinaris Medikus).

Detailed estimates of defoliation caused by spruce budworm [Choristoneura fumiferana (Clem.)] over the crown length of young balsam fir [Abies balsamea (L.) Mill.] were made throughout a spruce budworm outbreak from 1976 to 1984 in the Cape Breton Highlands, Nova Scotia. The results show no clear tendency for a particular level of the crown to be damaged more heavily than any other. Thus, there is no reason to continue the common practice of taking samples from the mid-crown level on the assumption that they represent an ‘average’ level of defoliation either for high or low populations. Sampling from the bottom of the crown should provide a more convenient and cost-effective approach for estimating defoliation.

The cabbage maggot, Delia radicum (L.), is a major root-infesting pest of cruciferous crops (Davidson and Lyon 1979). Current control methods include soil drenches with fensulfothion, carbofuran, and chlopyrifos (Matthews-Geringer and Hough-Goldstein 1988). Partial deterrency of oviposition by cabbage maggots was achieved using turpentinesoaked stakes (Havukkala 1982), and 3,5-dimethoxy-4-hydroxycinnamica cid, produced in the frass of a lepidopteran pest of cabbage (Jones et al. 1988). A blend of three monoterpenes (3-carene, limonene, and p-cymene) was found by Ntiamoah et al. (1996) to be the major oviposition deterrent for the onion maggot, Delia antiqua (Meigen), in a commercial pine oil, Norpine 65 (Northwest Petrochemicals, Annacortes, Washington). Our objectives were to evaluate this blend, and a more complex blend containing three additional constituents, as oviposition deterrents in the laboratory for the cabbage maggot.

In laboratory bioassays, four carabid species [Agonum dorsale (Pontoppidan), Bembidion lampros (Herbst), B. obtusum Serville, and Demetrias atricapillus (L.)] that are important predators of aphids in cereals in the United Kingdom were exposed to deposits of deltamethrin, dimethoate, or pirimicarb on glass for up to 72 h. We detected differences between compounds and species that are discussed in the context of exposure of these predators to insecticides in the field. We also describe problems involved in obtaining comparative toxicity data when dilutions of field application rates for target species are used in bioassays with nontarget species. Such problems add another dimension to risk assessment based on laboratory data.

We determined the distribution of root weevil larvae feeding on the roots of young ornamental conifers in field studies using a new non-destructive sampling technique. Most root weevil larvae fed on the roots during summer, fall, and late spring with significantly more larvae found at 10 cm than at 20 and 30 cm and more at 20 cm than at 30 cm. Larvae moved down into the soil to overwinter and moved closer to the surface (<15 cm) in the spring. Soil samples predicted the population density of larvae under individual trees. Four samples (0.0076 m3), 9 cm in diameter by 30 cm long, taken equidistantly 20 cm from the tree stem provided the best estimate. The equation, T = 64.04 M, where T is the total number of larvae beneath a tree, and M is the mean number of root weevil larvae from four soil samples, described the linear relationship between the number of larvae in soil samples and the total population of larvae beneath a tree. Implications for the timing and location of sampling and control measures are discussed.

Detoxicative enzyme systems, such as the cytochrome P450 monooxygenases, gluthione S-transferases, and general esterases, have been widely studied in holometabolous insects (e.g. Lepidoptera, Diptera, and Coleoptera). These, and other enzyme systems, play important roles in insecticide resistance, but are also important in insect–host plant relationships, because host range can partially depend on the ability of an insect to cope with putatively toxic allelochemicals in an otherwise suitable host plant (e.g. Lindroth 1989). In some cases, differences in the relative activities of these enzymes between closely related insect taxa can have significant biological consequences (Siegfried and Mullin 1989).

(E)-11,13-Tetradecadienal (E11,13-14:Ald) is the major component of the sex pheromone of the western blackheaded budworm (WBB), Acleris gloverana Walsingham. The compound was identified in extracts of the female’s pheromone gland by coupled gas chromatographic - electroantennographic detection (GC-EAD) and coupled GC - mass spectrometry in selected ion monitoring mode. In field experiments, E11,13-14:Ald by itself was attractive, but addition of (Z)-11,13-tetradecadienal doubled trap catches of male WBB. (E)-11,13-Tetradecadienol or (E)-11,13-tetradecadienyl acetate in binary or ternary combination with E11,13-14:Ald did not enhance attractiveness of the bait. In comparative assessments of five different trap designs, Uni-traps appeared to be the most suitable for use in pheromone-based monitoring of populations of WBB.

Sampling procedures for estimating within-tree populations of second-stage larvae (L2) of Matsucoccus feytaudi Duc., infesting maritime pine (Pinus pinaster Ait.), were investigated. These included random sampling without replacement, and systematic sampling with and without a linear model. The relative precision of the sampling was affected by the number, size, and bark thickness of the sample units. Because of symmetrical vertical distribution of within-tree populations, systematic sampling with a linear model did not increase precision when compared with simple systematic sampling. Sampling can be profitably reduced to below the crown portion of the bole, after removal of the part with either smooth or very thick and pyramidal bark. Counting L2 exuviae in the upper 10 cm of each 20-cm-long log, using one in every three logs, provided a relative precision of about 40%. The numbers of male M. feytaudi caught in sticky traps baited with 5 or 30 μg of synthetic pheromone were compared with the numbers of L2 estimated according to the sampling method previously developed. There was a significant positive correlation between number of scales caught and L2 estimates, at the level of individual trees for the lower dose lures, and at the level of groups of trees for the higher dose lures, used in 20-year-old stands. Large captures in younger, weakly infested stands were related to a possible immigration of flying scale insects.

The effect of four tillage regimes on the emergence of root maggots (Delia spp.) (Diptera: Anthomyiidae) was determined on experimental plots seeded the previous year to either Brassica rupa L. or Brassica napus L. The tillage regimes evaluated comprised no tillage, tillage in the spring only, tillage in the fall only, and tillage in both the fall and the spring. Emergence trap collections of Delia radicum (L.) and Delia floralis (Fallén) were made from the experimental plots from early May to mid-July of 1991 and 1992. In both years, emergence from untilled plots significantly exceeded that from plots subjected to any other tillage treatment. Tillage resulted in a decrease in emergence of 55–64% for D. radicum, and reduction of 53–72% for D. floralis. For D. floralis, greatest reductions in emergence following a tillage treatment occurred in plots tilled only in the fall or in plots tilled in both the fall and the spring; however for D. radicum, tillage in the fall, the spring, and in both the fall and the spring reduced emergence to approximately the same extent. Results of our study indicated that canola growers in regions of high population densities of root maggot should cultivate infested fields, preferably in fall, to reduce the emergence success of Delia spp.

An illustrated key is given to 28 genera, representing 10 families of at least 50 chalcidoid parasitoids and hyperparasitoids recorded from Choristoneura species (Tortricidae), or their primary parasitoids, in America north of Mexico. We include species reared throughout a 12-year study of the parasitoids and hyperparasitoids associated with the spruce budworm, Choristoneura fumiferana (Clemens), in New Brunswick, Canada, as well as those listed in various catalogs. Notes are provided for all the chalcidoid species, whether or not they are recorded in the literature. Nine species doubtfully or incorrectly recorded from Choristoneura species are also discussed.

Primary parasitoids belonging to the Ichneumonidae, Braconidae, and Tachinidae have been recorded from 10 of the 16 Nearctic Choristoneura species but chalcidoid parasitoids are recorded, usually as hyperparasitoids, from only four of the 16 species. The species of primary parasitoids of Choristoneura checked for records of parasitism by Chalcidoidea are tabulated by host species. Also listed are species of primary parasitoids serving as hosts for each of the chalcidoid species. We report 51 new host records of primary parasitoids and hyperparasitoids from C. fumiferana and its parasitoids collected in New Brunswick.

A new generic combination is given: Mesopolobus tortricis (Brues) comb.nov. from Psychophagus (proposed by Z. Boucek).

We tested the prediction that larvae of the fir coneworm, Dioryctria abietivorella (Groté), preferentially exploit cones previously damaged by cone maggots, Strobilomyia spp. In most years sampled, fir coneworm attacked a significantly greater proportion of maggot-damaged than healthy cones of both white spruce and black spruce. The ecological implications for pest management are briefly discussed.

Various biological parameters of Liriomyza trifolii (Burgess) were investigated to maximize mass-rearing efficiency of this insect. Average percentage emergence from a cohort of uniformly aged pupae was 90.0% of which 37.0% were males. A significant difference in the among-day emergence sequences from a pupal cohort was detected with 77.5% of all females and 80.1% of all males emerging during the first 2 days of the emergence sequence. Adults emerging on day 3 within the emergence sequence lived significantly longer than did flies emerging on the other days within the sequence. Male flies lived an average of 9.9 days or 33.1% less than the 14.8-day average for female flies. Cage size was also found to influence adult longevity significantly with the greatest average longevity (20 days for females and 12 days for males) occurring in 385.6-cm3 cages. Emergence time within an emergence sequence and the physical size of an experimental unit are two previously experimentally undocumented sources of variation influencing longevity of Liriomyza. A significant nonlinear relationship between the number of flies leaving the rearing cages (as a result of normal rearing procedures) and the daily number of pupal L. trifolii added to each cage was detected. From these biological parameters, a birth and death rate simulation model was developed to predict adult population sizes of L. trifolii within a mass-rearing program. The gender-specific simulation model consisted of adult emergence (quantified in terms of the adult emergence sequence from a known number of pupae entered into each rearing culture), and adult death rate (quantified in terms of the survivorship of adults within the culture and the number of adults escaping from the culture). The adult population sizes predicted by the simulation model were not significantly different from the average population sizes observed from the rearing cages in validation studies utilizing normal mass-rearing practices. Use of this model should reduce the effort expended on maintaining host populations for commercial mass-production of natural enemies of L. trifolii.