The poplar and willow borer, Cryptorhynchus lapathi (L.), known to be present in British Columbia since 1923, primarily attacks species of Salix L. (Salicaceae) and Populus L. (Salicaceae). Larvae bore into stems, causing them to break easily. The impact of the weevil has been rising in recent years because of the increasing importance of poplar and willow from both economic and ecological perspectives. We conducted a study at 45 locations in British Columbia to determine host use among native Salix spp. and the between- and within-tree dynamics of C. lapathi. There were 11 new host records, but the incidence of attack was similar among species. Attacked trees were larger in general and had more dead wood and stems, more adventitious branches per stem, more total breaks per stem, and more naturally caused breaks per stem than their attack-free neighbours. Breaks caused by C. lapathi tended to be slightly larger in diameter and lower on the stem than naturally caused breaks. Bases of stems were preferentially attacked, and C. lapathi selected large stems in which to oviposit. As large attack-free trees become less abundant, weevils apparently start to attack small-diameter stems. Although C. lapathi is adversely affecting the health of willows in British Columbia, there is no evidence that any Salix species is threatened by weevil-caused extinction.

Monitoring of adult flight patterns of the blueberry maggot fly, Rhagoletis mendax Curran, in New Jersey, indicated that the adults are active over a much longer period than previously reported. Captures on Pherocon AM traps over two seasons in wild sites and commercial fields of highbush blueberry, Vaccinium corymbosum L. (Ericaceae), showed that adult flies are present for most of the period from early July to early November. Trap captures in wild sites peaked during July–August, whereas in some commercial fields, peak captures were recorded in September. Emergence patterns were determined by collecting pupae from a wild site and a commercial field at the time of peak fruit infestation. The following year, the wild-site and commercial-field populations showed distinct emergence periods that were in broad agreement with trap captures at these locations. Comparison of an allozyme locus, using individuals collected in commercial blueberry fields, both on Pherocon AM traps and from infested fruit, confirmed that these populations were R. mendax and not any of the sibling species with a similar flight period. These data show that there are considerable phenological differences between some R. mendax populations. Given this plasticity, current debates on evolutionary mechanisms in flies of the genus Rhagoletis Loew should consider that the flight period of R. mendax is probably neither a major limiting factor in the use of hosts with different fruiting schedules nor an effective premating isolation mechanism with respect to other sibling species.

Callow adults of the pine shoot beetle, Tomicus piniperda L., were fed shoots of Scots pine, Pinus sylvestris L. (Pinaceae), to investigate the influences of shoot age and feeding duration on survival and weight of callow adults and to characterize the relationship between the volume of shoot tissue excavated and weight gain. Heavier callow adults had better survival than lighter ones, and survival was higher on current-year shoots than on 1-year-old shoots. A significant relationship was observed between the amount of tissue excavated by callow females on current-year shoots and their body weight gain, a trend not observed in callow males. These results suggest that beetle weight and survival may be reduced when availability of current-year shoots during maturation feeding is limited because of competition (i.e., during population outbreaks), thus negatively affecting the production of future generations.

The rate at which obliquebanded leafroller, Choristoneura rosaceana (Harris), larvae vacated feeding sites in apple, Malus domestica Borkhauser (Rosaceae), trees was determined by monitoring infested terminal foliage under field conditions. The overwintering and summer generations of C. rosaceana were monitored in two orchards in 1997 and 1998. Larvae vacated terminal feeding sites relatively frequently because 50% of the sites during the overwintering and summer generations were vacant 34 ± 6 °d (threshold = 6 °C) and 53 ± 10°d, respectively, after sites had been marked. Vacancy rates increased from the beginning to the end of the summer generation in 1997 but remained relatively constant throughout the summer generation in 1998. The differences between the 2 years were probably because of less precipitation and lower availability of actively growing terminal foliage at the end of the summer in 1997 than in 1998. Differences in larval development did not seem to contribute to differences in vacancy rate. Recolonization of growing terminals was also studied in the field by removing C. rosaceana larvae from terminals only (1997) and the entire tree (1998). In 1997 and 1998, larval recolonization of terminals and trees occurred, because 6–8 d after larvae were removed populations in removal and adjacent control trees were not significantly different. Frequent larval movement to actively growing terminal foliage with sublethal insecticide residues may increase larval survival and could slow resistance development by providing a refuge for susceptible insects.

The spotted tentiform leafminer, Phyllonorycter blancardella (F.), overwinters in a photoperiodically induced state of pupal diapause. The critical day length (50% of leafminers enter diapause) for P. blancardella from latitudes of about 42–44°N in southwestern Ontario was 14.25 h at an average August temperature (Environment Canada 1993) of 20°C (Trimble 1994). The development time of actively growing larvae decreased with increased temperature, whereas the development time of diapause-destined larvae was not affected by temperature at the critical day length, suggesting a strong interaction between photoperiod and temperature in the regulation of prediapause development (Trimble 1994). This paper describes the interaction of photoperiod and temperature in the regulation of the rate of egg and larval development of diapausedestined leafminers in the laboratory and in semi-natural conditions.

We released marked mature male flies of the apple maggot, Rhagoletis pomonella (Walsh), inside and outside of square blocks of apple trees, Malus domestica Borkh. (Rosaceae), to test the effect of orchard structure on the interception of flies by odor-baited red-sphere traps. The blocks were composed of large trees planted at low density, medium-sized trees planted at medium density, or small trees planted at high density. The experiment was carried out in six commercial apple orchards during summer in 1997 and 1998. Released flies moving into blocks were intercepted in large proportions by baited perimeter traps, thus preventing fly penetration into sphere-protected blocks. In 1997, proportions of intercepted flies were higher for traps in blocks of small and medium-sized trees than for traps in blocks of large trees. In 1998, a year with an unusually low fruit load, interception remained high, but there were no differences in proportions of flies intercepted by perimeter traps among blocks of trees of different sizes. Overall we conclude that the tendency of apple growers in Massachusetts to replace large trees planted at low density with small or medium-sized trees planted at high or medium density will not adversely affect behavioral control programs for apple maggot flies. In fact, this practice may enhance the effectiveness of these programs through increased interception of immigrant adults.

Field collections of over-wintering and summer adults and nymphs of Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), Lygus borealis (Kelton), and Lygus elisus Van Duzee were made weekly in five fields in Saskatchewan in 1998 and 1999. The crops sampled were alfalfa, Medicago sativa L. (Leguminosae), canola, Brassica napus L. (Cruciferae), and mustard, Sinapis alba L. (Cruciferae), at Vonda, and alfalfa and canola at Saskatoon. In alfalfa, the most abundant Lygus spp. found in May and June were over-wintering adult L. lineolaris and (or) L. borealis; the predominant species in mid-June to early July was L. borealis; and the population from mid-July to late August was dominated by L. lineolaris. In canola, adult populations of Lygus spp. were not found until mid-June. The predominant species, L. lineolaris, probably over-wintering adults, was first detected in canola at the early bud stage in late June to early July; high numbers of L. lineolaris adults occurred in canola in mid-August. Populations of Lygus spp. in organic mustard were negligible. Dissections of field-collected Lygus spp. nymphs revealed parasitism in up to 70% of the midsummer population in alfalfa. In contrast, less than 1% of the late-season Lygus spp. population, primarily L. lineolaris in canola and L. lineolaris and L. borealis in alfalfa, was parasitized.

The objectives of this study were to determine whether the spatial distribution of Melanoplus sanguinipes F., the most abundant species of grasshopper on rangeland in southern Idaho, varied annually in response to changing patterns of grazing and to investigate how vegetation affects the spatial distribution of low-density populations of M. sanguinipes at scales relevant to most rangeland-management activities. A lattice of 72 sites was established across nine pastures, covering approximately 5000 ha. At each site, densities of M. sanguinipes, percent canopy coverage by plant species, and percent forage utilization by livestock were estimated twice per year, in June when M. sanguinipes was in the nymphal stage and in August during the adult stage, for 4 years, 1991–1994. Spatial analyses of variance were used to evaluate the influence of grazing and vegetation type on densities of M. sanguinipes. In August of each year, densities of M. sanguinipes were lower on heavily grazed sites than on lightly grazed sites, except in 1993, when the opposite trend was observed. Above-normal precipitation in 1993 resulted in abundant growth of annual forbs and regrowth of grazed plants. The distribution of nymphs in June of 1993 and 1994 reflected the grazing patterns of the previous summer. Densities of M. sanguinipes were lower on crested wheatgrass habitats than on annual grasslands for every sampling period from June 1991 to June 1993, after which no differences were observed. We interpret the results to suggest that grazing effects on low-density populations of M. sanguinipes were contingent on weather conditions; under dry conditions, grazed habitats were less favorable to M. sanguinipes but, during relatively cool wet summers, grazing created conditions that were more favorable to M. sanguinipes.

Low seed set is a serious problem in seed orchards of lodgepole pine (Pinus contorta var. latifolia Engelmann) in the southern interior of British Columbia. We tested the hypothesis that Leptoglossus occidentalis Heidemann is responsible for the low seed set. Cones enclosed in insect exclusion bags as part of a pollination experiment produced significantly more filled seeds per cone than cones that were not bagged. In a separate bagging experiment, cones that were enclosed with a L. occidentalis female and her progeny produced only about one filled seed per cone, compared with about 28 seeds in bagged control cones. Changes in microclimate associated with the use of bags did not appear to be responsible for the observed increase in seed set in bagged cones. Leptoglossus occidentalis was also excluded from trees using the insecticide fenvalerate. Cones on fenvalerate-treated trees produced > 11 filled seeds per cone, whereas water-treated (control) cones produced < 1.7 filled seeds. These data suggest that L. occidentalis should be considered a serious pest in lodgepole pine seed orchards.

The sex pheromone of the obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), from the Niagara Peninsula, Ontario, was investigated using chemical analysis, GC–EAD, and field trapping experiments. The pheromone gland contained: (Z)-11-tetradecenyl acetate (Z11-14:Ac), (E)-11-tetradecenyl acetate (E11-14:Ac), (Z)-11-tetradecen-1-ol (Z11-14:OH), and (Z)-11-tetradecenal (Z11-14:Al). The average amounts of Z11-14:Ac, E11-14:Ac, Z11-14:OH, andZ11-14:Al were 40.40, 0.83, 0.47, and 0.13 ng/female, respectively. Eight other structurally related compounds, (E)-11-tetradecenal (E11-14:Al), (E)-11-tetradecen-1-ol (E11-14:OH), pentadecan-2-one (15-2kt), hexadecanal (16:Al), hexadecan-1-ol (16:OH), heptadecan-2-one (17-2kt), octadecanal (18:Al), and octadecyl acetate (18:Ac), were also identified. In a field trapping experiment, adding Z11-14:Al to lures containing a 100:3:5 blend of Z11-14:Ac, E11-14:Ac, and Z11-14:OH in an amount equal to 2% of the main component significantly increased the number of moths captured in apple, Malus domestica (Borkh.) (Rosaceae), orchards. The removal of Z11-14:Al from lures containing a 100:2:1.5:1 blend of Z11-14:Ac, E11-14:Ac, Z11-14:OH, and Z11-14:Al resulted in a > 50% reduction in the average total number of moths captured in a trap. This study provides the first evidence that Z11-14:Al is present in the pheromone of an eastern North American population of C. rosaceana.

For bark beetles (Coleoptera: Scolytidae) breeding in fallen trees, the tree characteristics that are associated with higher breeding densities are poorly known. The breeding densities of Douglas-fir beetles, Dendroctonus pseudotsugae Hopkins, in freshly felled Douglas-fir, Pseudotsugae menziesii (Mirb.) Franco, were examined with respect to tree diameter, phloem thickness, and several measures of tree growth rate over the past year to 10 years prior to tree death. Trees were felled in 8 decks of 3–12 trees to provide a range of tree qualities in a given location. Stepwise regression revealed that of the tree characteristics measured, only diameter was needed to explain the density of beetle attacks on trees within decks. Because diameter, phloem thickness, and growth-increment measures were all highly correlated, attack density also increased with phloem thickness and growth rate prior to felling when these measures were analyzed individually. The apparent preference for larger trees with thicker phloem is consistent with published results for live trees, but the positive effect of tree growth rate prior to death is contrary to results for beetles attacking live trees. Thus, assessments of stand susceptibility to bark beetles based on tree growth rate may differ depending on whether beetles are initially breeding in live or dead trees.

Over 250 durum wheats, Triticum durum Desf., and close relatives were screened for resistance to the wheat midge, Sitodiplosis mosellana (Géhin). Less than 2% showed consistently reduced egg and larval densities in field and laboratory trials. Two related accessions named ’Kahla’ had stable, low larval infestation levels, which were about 30% of those in commercial durum wheat cultivars. No antibiosis was detected in durum wheats. The reduction in infestation by larvae was associated with a similar reduction in oviposition. The resistance reduced egg densities by 80% or more in choice and no-choice laboratory tests and by about 70% in the field. Egg group size was not affected, and therefore reduced oviposition must have resulted from the number of egg groups deposited by females. The resistance was not associated with any of 12 morphological traits that were quantified for spikes. ’Kahla’ is the first durum wheat identified to have resistance against the wheat midge.

Eighteen parasitoid species were found associated with obliquebanded leafroller, Choristoneura rosaceana (Harris), and three-lined leafroller, Pandemis limitata Robinson, from 1982 to 1984, on apple and other host plants in the southern interior of British Columbia. The leafroller parasitoids included a Glypta Gravenhorst species (Hymenoptera: Ichneumonidae), Diadegma eureka (Ashmead) and Diadegma interruptum pterophorae (Ashmead) (Hymenoptera: Ichneumonidae), and Hemisturmia tortricis (Coquillett) (Diptera: Tachinidae). The two leafroller species were found on 18 wild host plants from 10 plant families.

In field and laboratory tests the wheat midge, Sitodiplosis mosellana (Géhin), oviposited and developed on all 43 accessions of 17 species of diploid, tetraploid, and hexaploid wheats, Triticum L. spp. Ancestral diploid wild wheats had the lowest infestations among species in the genus, and two hexaploid species, Triticum sphaerococcum Percival and Triticum zhukovskyi Men. and Er., were more heavily infested than common wheat, Triticum aestivum L. In five lineages recognized in the genus, infestation increased in association with domestication, although not always in a continuous way. The level of infestation was not related to seed size or the number of seeds in spikes. Wheat species with free-threshing seeds and compact spikes were more infested by larvae than ancestral wheat species with less compact spikes and glumes that were either affixed to or pressed tightly against the seed. An association between glume tightness and spike compactness may explain the positive correlation between susceptibility and spike compactness. Domestication increased the susceptibility of crop wheats to wheat midge, possibly because the free-threshing trait affects the suitability of the glume–seed interface for oviposition and establishment of larvae on the seeds. The ancestral cultivated wheats, Triticum spelta L. and Triticum dicoccoides Körn., are promising sources of resistance to wheat midge because they have the same genomes as modern wheats and relatively low susceptibility. One free-threshing accession of Triticum dicoccum Schrank had relatively low susceptibility to wheat midge and may provide a source of resistance.

The pheromone communication systems of azinphosmethyl-susceptible (susceptible) and azinphosmethyl-resistant (resistant) obliquebanded leafrollers, Choristoneura rosaceana (Harris), from the Niagara Peninsula of Ontario, were compared in the laboratory and field. The pheromone glands of resistant females contained approximately one-half as much (Z)-11-tetradecenyl acetate (Z11-14:Ac), (Z)-11-tetradecenol (Z11-14:OH), and (Z)-11-tetradecenal (Z11-14:Al) as the glands of susceptible females. A similar amount of (E)-11-tetradecenyl acetate (E11-14:Ac) was found in the glands of the two types of females. The pheromone effluvium from resistant females contained approximately one-half as much Z11-14:Ac, E11-14:Ac, Z11-14:OH, and Z11-14:Al as the effluvium from susceptible females. The onset and duration of female calling and the effect of age on calling were similar in susceptible and resistant C. rosaceana. In an apple orchard, traps baited with resistant females captured approximately one-half as many marked and released susceptible and resistant males as traps baited with susceptible females. There was no difference in the response of antennae from susceptible and resistant males to synthetic Z11-14:Ac and E11-14:Ac. The antennae of resistant males were less sensitive to Z11-14:OH and Z11-14:Al than the antennae of susceptible males. In a flight tunnel, pheromone-gland extracts from susceptible and resistant females, and calling susceptible and resistant females, were equally attractive to both susceptible and resistant males. In an apple orchard, the rate of capture of marked and released susceptible males was greater than that of resistant males in traps baited with susceptible females, but not in traps baited with resistant females or in traps baited with synthetic pheromone. The reduced ability to locate virgin females suggests that the presence of resistant males in an apple orchard may result in a reduction in the capture of moths in pheromone-baited traps. The reduction in trap catch was likely not caused by resistant females because they were less attractive to males than susceptible females and would therefore, in theory, compete less with traps for males than susceptible females. The differences observed in the pheromone communication systems of susceptible and resistant C. rosaceana are likely pleotropic effects associated with the selection for insecticide resistance.

In North America, the life cycle of the European earwig (Forficula auricularia L.) can be divided into a nesting phase (hypogean phase) and a free-foraging phase (epigean phase) (Crumb et al. 1941; Behura 1956; Lamb and Wellington 1975). Adults spend the nesting phase in the soil; females burrow into the ground at the onset of the cold weather, lay eggs, and then care for the eggs. Hatching occurs in spring; first- or second-instar nymphs move to the soil surface for the free-foraging period. The earwig, a nocturnal insect, spends the entire daylight period of hiding under trash or in dark crevices. Where two broods occur, females reenter the ground a second time (Lamb and Wellington 1975). Stomach content analyses (Crumb et al. 1941; Sunderland and Vickerman 1980) and food preference tests (McLeod and Chant 1952; Buxton and Madge 1976) revealed that the European earwig is omnivorous. Under laboratory conditions, nymphs fed freshly frozen aphids, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), survive better than those fed green algae or carrots, develop faster, and produce heavier females (Phillips 1981; Carrillo 1985).

The European apple sawfly, Hoplocampa testudinea (Klug), is a pest of apple, Malus pumila Bork. (Rosaceae), in orchards. Introduced from Europe onto Long Island, New York, in 1939, it gradually invaded the New England states (Pyenson 1943). Downes and Andison (1942) also reported the apple sawfly on Vancouver Island in 1940. In 1979, H. testudinea was discovered for the first time in southern Quebec (Paradis 1980), after which it spread throughout the apple-growing areas of this province (Vincent and Mailloux 1988). There are no published records on any natural enemies of H. testudinea in North America.

We studied the effects of frost on the survival rate of European earwigs, Forficula auricularia L., during the underground phase of their cycle and determined the timing of oviposition, hatching, and death of the adults; we selected couples and inserted them into the ground to a depth of 150 cm in an open area and along the foundations of a heated suburban house in the Montréal area. Oviposition occurred in November and December, and eggs hatched between January and early June, after an average incubation period of 79–189 d depending on experimental conditions. In the open area all adults and eggs at ground surface died, killed by frost, whereas those in the soil along the house foundation did not die. Males died during the fall and early winter; their longevity was shorter than that of females, which survived until shortly after egg hatch. Females and eggs survived temperatures as low as − 3 and − 2 °C, respectively. For successful reproduction, females must keep their developing eggs at a temperature low enough to delay hatching until mid-April.

Dendroctonus ponderosae (Hopkins) is widely distributed across western North America, feeding in at least 12 native species of Pinus L. (Pinaceae). We investigated the existence of heritable differences in two life-history parameters (adult size and development time) of D. ponderosae from a northern population (central Idaho, Pinus contorta Douglas ex Loudon) and a southern population (southern Utah, Pinus ponderosa Douglas ex P. and C. Lawson). We attempted to separate heritable from environmental effects by rearing individuals from both populations through two generations (F1 and F2) in a common standardized laboratory environment with a constant temperature. Two treatment effects were tested for in the F2 generation: (1) geographic location (source host) for F0D. ponderosae; and (2) the F2 brood host. We hypothesized that, if differences were observed and the F0 source host and region had a greater effect on F2 brood development time and adult size than did the host in which F2 brood were reared, a heritable factor related to the F0 parents was responsible. Time to emergence was significantly shorter for second-generation offspring of the northern population than for second-generation offspring of the southern population, regardless of the F2 brood host. Although both the F2 brood host and F0 source parents were significant in explaining differences observed in the developmental-time distribution of F2 brood, the F0 source effect was found to be much greater. Also, F2 males and females from southern source parents were significantly larger than F2 brood from northern source parents when reared in both F2 brood hosts. Geographic region and original host of F0 source parents had a significant effect on F2 offspring size, whereas the immediate food for F2 brood was not significant in explaining differences. These results suggest genetically based regional differences in D. ponderosae populations.

The balsam twig aphid, Mindarus abietinus Koch, is a major pest of balsam fir, Abies balsamea (L.) Mill. (Pinaceae), grown as Christmas trees in eastern Canada and the United States (Nettleton and Hain 1982; Kleintjes 1997). This aphid has three or four generations from April to July, and overwinters as eggs on fir shoots. Mature fundatrices deposit progeny on new shoots in late May. Infested shoots develop into pseudogalls characterised by stunting and needle distortion, thus reducing the aesthetic value of trees.