A 5-year survey of Saskatchewan alfalfa (Medicago sativa L. sensu lato) seed fields was undertaken to determine the level of infestation by the alfalfa seed chalcid, Bruchophagus roddi (Gussakovsky). Seed samples were taken from commercial seed fields, hay fields, and roadsides just before pod maturity. From sample lots of 250 pods, the numbers of healthy, chalcid-damaged, and frozen or immature seed were determined. Later, producers were questioned about the attributes of and management practices employed in their fields. Seed yields and infestation levels were correlated with temperature, precipitation, and degree-day data from the year of and the year preceding seed collection. Alfalfa seed chalcid infestation level was correlated most closely with the temperature and rainfall in July and August of both years. The proportion of damaged seed was highest the year following warm, dry summers. Alfalfa cultivar also influenced infestation levels; winter-hardy cultivars that became dormant early in the autumn had lower levels of chalcid-damaged seeds than less hardy cultivars which maintained growth later in the season. Management practices such as the use of insecticides (for plant bug and aphid control), fertilizers, and herbicides, size or age of field, soil type, and application of irrigation water did not affect the proportion of seeds injured by chalcids.

Overwintering mortality in the spruce budworm, Choristoneura fumiferana (Clem.), was measured between 1983 and 1990 in several natural stands of balsam fir, Abies balsamea (L.), in Quebec and Ontario. Overwintering losses (disappearance of larvae) averaged 25.2%, occurred mostly in late summer and early fall, and were probably caused by, in large part, failure to spin a hibernaculum, diapause-free development, and invertebrate predation. An average of 24.1% of larvae were found dead in the hibernaculum. This mortality also occurred early in diapause and during post-diapause development, and overwintering mortality did not vary much from year to year. We conclude that overwintering mortality does not result from adverse winter weather conditions or from gradual loss of hibernacula. Overall overwintering mortality from the loss of hibernating larvae plus death within the hibernaculum averaged 43.2% and was not related to infection with the microsporidian Nosema fumiferanae (Thomson). We observed no influence of position in the tree crown on overwintering survival. There was a 40% decrease in overwintering survival among larvae from eggs laid very late in a female’s oviposition sequence. Survival within the hibernaculum on shoots of A. balsamea bearing different types of spinning substrates varied considerably, and was highly correlated with larval spinning preferences. Shoots bearing lichen mats, rough bark, male flower scars, or 1-year-old annular scales were most suitable, whereas shoots bearing annular scales older than 1 year or smooth bark were least suitable. The efficiency of the NaOH extraction technique to recover overwintering spruce budworm larvae was found to be highly variable, and to depend on population density, shoot type, and the proportion of live larvae on the branches.

The Agabus semivittatus-group is revised. The group, which is restricted to temperate North America, contains six species: Agabus semivittatus LeConte, which is almost transcontinental; Agabus johannis Fall in peninsular Florida; Agabus astrictovittatus new species along the Atlantic coast from New York to northern Florida and Alabama; Agabus stagninus (Say) along the Atlantic coast from New York to Florida and along the Gulf of Mexico coast to Louisiana; Agabus flavovittatus new species with a wide distribution east of the Great Plains, from southern Ontario to Mississippi and eastern Texas but not along the Atlantic coast; and Agabus texovittatus new species in Texas. Agabus stagninus and A. flavovittatus hybridize in southeastern Pennsylvania. The placement of Agabus texanus Sharp as a junior synonym of A. semivittatus is confirmed. A lectotype is designated for Agabus spilotus LeConte (= A. semivittatus). A neotype is designated for A. stagninus. A key to species is presented and, for each species, the following information is provided: description; illustrations of taxonomically important characters; morphological measurements on selected population samples; notes on relationships, variation, and ecology; and a map of collection localities. A cladistic analysis of the relationships of the group within Agabus indicated that the americanus-, spinipes-, and confusus-groups belong to the same clade as the semivittatus-group and that the seriatus-group is sister to this clade. Within the semivittatus-group, there are three well-defined subgroups as follows: A. semivittatus; A. johannis and A. astrictovittatus; and A. stagninus, A. flavovittatus, and A. texovittatus.

The Colenis of the United States and Canada are reviewed. Three new species are described: Colenis (Colenis) bifida n.sp., Colenis (Colenis) stephani n.sp., and Colenis (Colenis) ora n.sp. The Colenis subgenus name Carcharodes Hlisnikovsky is preoccupied: Colenodes is proposed as a replacement name.

Three cereal aphids, Rhopalosiphum padi (L.), Schizaphis graminum (Rondani), and Sitobion avenae (F.), invade wheat fields in the northern Great Plains each spring, and populations occasionally reach economic levels. The first objective of this study was to describe the spatial distribution of three species of cereal aphids infesting hard red spring wheat (Triticum aestivum L.). The second objective was to develop two sampling plans for cereal aphids using individual stems as the sampling unit, a sampling plan with fixed levels of precision and a sequential sampling decision plan based on total numbers of aphids present. Aphid population estimates were collected from 47 eastern North Dakota spring wheat fields during 1993–1995. The number of aphids per stem were counted on 100–350 stems per field. Taylor’s power law and Iwao’s patchiness regression were used to analyze the spatial distribution of the aphids. Rhopalosiphum padi and S. avenae exhibited an aggregated distribution, whereas S. graminum was distributed randomly in the field. Taylor’s power law provided a better fit to the data than Iwao’s patchiness regression. Sample size requirements for precision levels of 0.10, 0.15, and 0.25 were estimated with Taylor’s regression coefficients. Required sample sizes increased with decreased aphid populations and increased levels of precision. The two sampling plans presented should be useful for research on cereal aphid population dynamics and pest management decision making in spring wheat.

The life history of the white pine cone borer, Eucosma tocullionana Heinrich, was studied from 1992 to 1994 in an eastern white pine seed orchard in Ontario. Adults flew from late May to early July, and egg laying commenced in mid-June. Oviposition coincided with the onset of white pine pollen release. Eggs were laid singly or in clusters on cones, with most of the eggs laid on the basal third of the cone. Head capsule measurements indicated five instars. Larvae fed in cones from mid-June to the end of August. Mature larvae exited the cones and dropped to the ground to pupate. The insect is univoltine. Parasitism by the Hymenoptera, Trichogramma and Apanteles, accounted for 5% of the eggs and 1% of the larvae, respectively. About 40% of the larvae died from being entrapped in resin. There were no significant differences in attack rates by E. tocullionana within the tree except in the middle level, where the south quadrant had significantly higher rates than the north quadrant.

A set of six microprocessor-controlled mini-environmental chambers (0.04 m3 each) was designed, built, and tested. Chambers are capable of subfreezing temperatures (less than −10 °C) and can operate under constant or time-varying temperature regimes. Chambers are cooled by circulating ethyl alcohol from a reservoir chilled by an immersion cooler. Heat is provided by 17-W cartridge heaters. Temperatures are independently controlled by a single IBM 8088 computer instructing a data acquisition and control system. A single photoperiod is maintained by a commercial timer activating two miniature light bulbs in each chamber. Chamber temperatures were within 0.5 or 0.75 °C of the set temperature 65 or 94% of the time, respectively, during a 39-d test period. Minimum temperature capabilities were estimated for a variety of chamber configurations by an examination of the thermodynamic characteristics of the system.

The bertha armyworm, Mamestra configurata Walker, is a major pest of canola in western Canada. In 1994, 1995, and 1996 more than 670 000, 650 000, and 250 000 ha of canola were sprayed for bertha armyworm, respectively (Anonymous 1994, 1995, 1996). Despite the current trend towards increased acreage of canola production in western Canada, canola acreages declined markedly in 1996 from that planted in 1995 (Saskatchewan Agriculture and Food Statistical Facts 1996) in part because of the perception by farmers of the impact of bertha armyworm outbreaks in 1994 and 1995. Much research has been carried out in western Canada on the bertha armyworm with the aim of developing an integrated pest management program which includes the understanding of its biological control agents. Turnock (1984) reported that the native parasitoid complex of larval M. configurata consists of five species of Hymenoptera and 10 species of Diptera. Only two of these, namely Banchus flavescens Cresson (Hymenoptera: Ichneumonidae) and Athrycia cinerea (Coquillett) (Diptera: Tachinidae), have large negative impacts on its populations (Wylie and Bucher 1977).

The spruce budworm, Choristoneura fumiferana (Clem.), nuclear polyhedrosis virus (CfMNPV) has been studied extensively for its potential use as a bio-insecticide (Cunningham 1995). Recent advances in recombinant DNA technology have been impetuous in the genetic engineering of this virus to increase its virulence and (or) speed of action. This aspect of research has been concentrated on the modification of a plaque purified (Ireland strain) isolate obtained from the wild-type virus population (Arif et al. 1984). To assess any improvement in the effectiveness against the target pest, the virulence of the unaltered virus must first be determined. Bioassay results that have been previously reported by Kaupp and Ebling (1990) were conducted on the wild-type virus found in nature which consists of a mixture of viruses (Arif et al. 1994). Results of bioassays conducted to determine dose–response and time–response of fifth-instar spruce budworm larvae to the Ireland strain of CfMNPV are reported here.

The apple leaf midge, Dasineura mali (Kieffer), is an apple pest in Nova Scotia's Annapolis Valley (Rogers 1991). Larval D. mali are specialist, leaf-feeding pests that attack primarily young pubescent apple shoots. Larval feeding induces the leaves to curl tightly toward the midrib and form distinctive reddish galls that desiccate following larval exit. Economic damage to orchards in Annapolis Valley has not been estimated, but immature trees and nursery stock are vulnerable because new growth is essential for proper tree formation (Rogers 1991).

Gilbert and Raworth (1996) propose a general theory to explain the effects of temperature on the development and growth rates of insects. The theory is evolutionary rather than physiological. They propose that insects are selected for a high rate of increase (i.e., rapid growth and large size) in spring, and for rapid development in summer. They claim that these selection pressures explain five “puzzles:” (1) the linearity of the relationship between development rate and temperature, (2) a reduction in the genetic variation of development rate at high temperature (i.e., average midsummer temperature), (3) a reduction in the genetic variation of growth rate at low temperature (i.e., average spring temperature), (4) slow development at the time of emergence after overwintering, and (5) a greater reduction in development rate than growth rate at low temperature.

Pieris rapae (L.) (Lepidoptera: Pieridae) is endemic in the Canary Islands, presumably since Roman times. Average temperatures at sea level on Tenerife and La Gomera range from 17°C at midwinter to 25°C in summer. If the argument of Gilbert and Raworth (1996) is correct, we might expect the development threshold of P. rapae in the Canaries to be 17°C, much higher than the 10°C observed elsewhere: Cambridge, U.K.; Cordoba, Spain; Pompei, Italy; Montpellier, France; Vancouver, Canada; and Canberra, Australia (Gilbert 1988).