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The potential for mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae), to expand its historical range in North America from west of the continental divide into the eastern boreal forest was assessed on the basis of analyses of the effects of climate and weather on brood development and survival, and key aspects of the interaction of mountain pine beetle with its hosts and associated organisms. Variation in climate suitability and high host susceptibility in the boreal forest create a finite risk of establishment and local persistence of low-level mountain pine beetle populations outside their historical range. Eventually, these populations could become widespread and cause epidemic infestations, creating an ecological pathway eastward through the boreal forest. Such infestations would reduce the commercial value of forests and impose an additional disturbance on native ecological systems.
Systematics & Morphology / Systématique et morphologie
Two species of Androprosopa Mik are reported from Mexico, one of which is newly described (A. zempoalasp. nov.). This new species is related to a small group of western Nearctic species defined by a pair of posterolateral hook-like epandrial processes.
A molecular and biometrie assessment and redescription of Myzodium mimulicola (Drews and Sampson) are provided. New North American host and distributional data are presented, including the first record from Alaska. Myzodium knowltoni (Smith and Robinson) is a junior subjective synonym of M. mimulicola, based on molecular-sequence and morphological evidence. A key to the known Myzodium species (apterae and alatae) is included.
Pheromone lures for eastern and western blackheaded budworms, Acleris variana (Fernald) and A. gloverana (Walsingham), were synthesized and deployed in traps at locations with decreasing and increasing populations of western blackheaded budworms in British Columbia, Canada. Traps baited with these lures caught comparable numbers of moths at all sites tested in each year. The lures were sensitive to changes in density of budworm populations below observable damage levels, and numbers of moths in traps were strongly correlated with independent estimates of egg densities in the same year. The results confirm the qualitative similarity of the sex pheromones in eastern and western species of blackheaded budworm and demonstrate their utility as a tool for monitoring population trends, including increases in populations to damaging levels.
We collected midcrown branches of balsam fir, Abies balsamea (L.) Mill. (Pinaceae), at six different sites located in five different plant-hardiness zones, along a north—south transect in New Brunswick, Canada, to evaluate the effect of plant-hardiness zone, crown class (overstory versus understory), and shoot length during the previous 10 years on the annual incidence of gouting by the balsam woolly adelgid, Adelges piceae (Ratzeburg) (Homoptera: Adelgidae). Site, crown class, and their interaction, along with the square of shoot length, explained 78% of the variation in gouting. Variations in gouting attributed to plant-hardiness zone were probably primarily due to variation in mean January temperature: at each site, the mean January temperature was positively and closely related to the mean level of gouting. The level of gouting was consistently higher on trees in the understory than on those in the overstory. Shoot length was parabolically related to the proportion of shoots with gout. The parabolic relationship between shoot size and the level of gouting is similar to that previously reported for galling adelgids, and suggests that gouting by A. piceae may be greatest on trees with an intermediate growth rate.
We monitored 12 colonies of the nomadic social caterpillar Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae) on trembling aspen, Populus tremuloides Michx. (Salicaceae), under field conditions in spring 2007. We examined cohesion and synchronization of colonies and spatiotemporal activity patterns to compare foraging in the field with the results of laboratory studies and with foraging by central-place foragers. All colonies were highly cohesive; fragmentation was observed only three times. Activity was highly synchronous within colonies, with clear alternation between periods of activity and quiescence. Colonies performed 4.25 ± 0.12 (mean ± SE) activity bouts per day, and foraging was more likely to occur in the early morning than at midday. Colony activity was weakly correlated with temperature. In contrast to that of M. americanum (F.), the foraging schedule was flexible: foraging was observed at all recorded times and temperatures. Colonies searched for a new feeding site every 2.54 ± 0.37 days (mean ± SE) after a food source was depleted. Time spent at a food source decreased with colony size, and distance travelled between food sources increased with instar. Malacosoma disstria caterpillars on trembling aspen are not very selective; rather, they minimize movement, thus decreasing potential contacts with predators.
We investigated whether or not pear ester (ethyl (E,Z)-2,4-decadienoate) attracted adult oriental fruit moths, Cydia molesta (Busck) (Lepidoptera: Tortricidae). The electro-antennographic responses of C. molesta to pear ester were recorded and dose—response curves calculated. In laboratory bioassays, the attractiveness of different dosages was assessed in a dual-choice olfactometric arena. The responses of virgin males and females to pear ester in the presence and absence of pear (Pyrus communis L.), peach (Prunus persica (L.) Batsch.), and apple (Malus ×domestica Borkh.) (Rosaceae) shoots were evaluated. Electroantennographic recordings demonstrated that both male and female C. molesta were able to detect the pear ester. In our bioassay, however, pear ester readily attracted males but attracted very few females. The response of males was dose-dependent and they preferred pear ester over apple-and pear-shoot volatiles, whereas no apparent preference between pear ester and peach-shoot volatiles was observed. Therefore, this kairomonal compound could be more effective in attracting C. molesta when applied in orchards of secondary host plants, like apple or pear, than in peach orchards.
Western boxelder bugs, Boisea rubrolineata (Barber), form large aggregations on pistillate boxelder, Acer negundo L. (Aceraceae), host trees with maturing seeds, and cluster on warm, sunlit surfaces prior to overwintering. We have recently shown that B. rubrolineata is attracted to the host-tree semiochemicals phenylacetonitrile and 2-phenethyl acetate. We report results of chemical analyses and laboratory bioassays suggesting that aggregation and sexual communication in B. rubrolineata are mediated by 2-phenylethanol. This compound serves as an aggregation pheromone for females, males, and 5th-instar nymphs in midsummer, and in males it appears to serve as a sex-attractant pheromone in early spring. As an aggregation pheromone, 2-phenylethanol originates from the feces of seed-feeding females and males and (or) the ventral abdominal gland of males. As a sex-attractant pheromone, it originates from the ventral abdominal gland of males that emerge from overwintering diapause. Aggregations of B. rubrolineata in the fall and winter are mediated by other as yet unknown pheromones.
The triterpenoid saponins soyasaponin I, dehydrosoyasaponin I, echinocystic acid 3-glucoside, β-escin, glycyrrhizic acid, hederacoside C, and α-hederin were tested alone and in combination with insecticidal PA1b peptide mixtures isolated from peas for their effects on the feeding and survival of a stored-product insect, the rice weevil, Sitophilus oryzae (L.). There were two sources of peptides: a purified extract composed primarily of PA1b peptides and a partially purified extract (C8 extract) that contained mainly peptides and lesser amounts of soyasaponin I, dehydrosoyasaponin I, and other compounds. Dehydrosoyasaponin I, echinocystic acid 3-glucoside, α-hederin, and β-escin were active (causing reduced feeding and increased mortality) when used alone. Soyasaponin I, hederacoside C, and glycyrrhizic acid were inactive when used alone. Purified peptides and C8 extract were active when used alone. The mixtures of the inactive soyasaponin 1 and the active peptides were as active as peptides alone, even when peptides composed only 10% of the mixture. Similar trends were seen with the mixtures of β-escin and PA1b. In general, the mixtures of saponins and peptides were synergistic. Possible modes of synergistic action are discussed.