Registered users receive a variety of benefits including the ability to customize email alerts, create favorite journals list, and save searches.
Please note that a BioOne web account does not automatically grant access to full-text content. An institutional or society member subscription is required to view non-Open Access content.
Contact firstname.lastname@example.org with any questions.
Phytoplasmas are bacterial plant pathogens consisting of more than 50 phylogenetic groups that cause devastating diseases in various crops worldwide. They are obligate parasites restricted to the phloem tissue of the host plant and are transmitted from plant to plant mostly by leafhoppers (Hemiptera: Cicadellidae). They reproduce within the tissues of their insect vectors and are transferred in the salivary secretions to new host plants during feeding. Phytoplasma epidemiology involves a tritrophic relationship between the pathogen and usually several hosts and vectors. The host-plant range depends on the number of vectors, their feeding habits, and their dispersal pattern. Interactions between phytoplasmas and their vector hosts are complex and influenced by insects' vectoring abilities and the consequences of infection for vectors. In Canada, seven phytoplasma taxa have been detected in various crops. Aster yellows, the primary vector of which is the leafhopper Macrosteles quadrilineatus (Forbes), is the most common and widespread. X-disease, transmitted by at least eight leafhopper species, is economically damaging to all cultivated species of Prunus L. (Rosaceae). Clover proliferation, also transmitted by M. quadrilineatus, is the causal agent of important diseases such as clover proliferation and alfalfa witches’ broom. Ash yellows and pear decline have caused economic problems for several decades, while bois noir, a quarantinable disease in Canada, was detected in Ontario and British Columbia for the first time only recently. Because of their cryptic nature, phytoplasmas are difficult to manage; quarantine measures and insecticide sprays remain the most common control measures. However, integrated pest management techniques using beneficial insects, biotechnology, and plant resistance are emerging.
Fig-pollinating wasps are phytophagous wasps that mainly use olfaction to locate their fig (Ficus L., Moraceae) hosts. To provide a morphological framework for studying agaonid olfaction, we examined the antennal sensilla of female Ceratosolen solmsi marchali Mayr by scanning and transmission electron microscopy. We identified and characterized (ultrastructure, distribution, abundance, and position) 13 types of sensilla: multiporous placoid sensilla (types 1 and 2), basiconic sensilla (types 1 and 2), basiconic capitate peg sensilla, sensilla chaetica (types 1–3), sensilla trichodea, sensilla coeloconica (types 1–3), and one specialized sensillum regarded as a sensillum obscurum. We suggest that five types are chemoreceptors because they are porous and innervated by multiple sensory neurons. Sensilla coeloconica type 1 may also function as chemoreceptors, based on external morphology. Other sensilla may be involved in mechanoreception, thermo- and (or) hygro-reception, or pressure detection. We discuss our results in relation to the lifestyle of C. solmsi marchali.
Morphometric techniques, DNA mitochondrial cytochrome c oxidase subunit 1 gene (COI) barcoding, and microsatellite flanking region sequences were used to assess the reliability of suggested morphological characters in distinguishing the green apple aphid (Aphis pomi De Geer) from the spirea aphid (Aphis spiraecola Patch), and to assess variation within these species. Both molecular approaches clearly distinguished two groups corresponding to the morphologically defined species. Differences in the length of the distal rostral segment and the number of lateral tubercles were found to be robust indicators of species membership, performing as well as multivariate approaches. Among A. pomi samples, microsatellite flanking region sequences were relatively uniform, whereas A. spiraecola exhibited much variability, which suggests that North American populations of the latter species are genetically much more complex.
Two new ichneumonid species in the genus Jezarotes Uchida are described from Korea: J. dentatusnn. sp. and J. tetragonisnn. sp. Photographs of diagnostic characters of the two new species, a key to the six known species, and a diagnosis of the genus are provided.
The perpetuation of symbiotic associations between bark beetles (Coleoptera: Curculionidae: Scolytinae) and ophiostomatoid fungi requires the consistent transport of fungi by successive beetle generations to new host trees. We used scanning electron microscopy and culture methods to investigate fungal transport by the mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins. MPB transports its two main fungal associates, Grosmannia clavigera (Robinson-Jeffrey and Davidson) Zipfel, de Beer and Wingfield and Ophiostoma montium (Rumbold) von Arx, in sac-like mycangia on the maxillary cardines as well as on the exoskeleton. Although spores of both species of fungi were observed on MPB exoskeletons, often in pits, O. montium spores were generally more abundant than G. clavigera spores. However, a general scarcity of spores of either species on MPB exoskeletons compared with numbers on scolytines that lack sac-like mycangia indicates that fungal transport exteriorly on MPBs is incidental rather than adaptive. Conidia were the dominant spore type transported regardless of location or species; however, our results suggest that once acquired in mycangia, conidia may reproduce in a yeast-like form and even produce hypha-like strands and compact conidiophore-like structures. Fungi that propagate in mycangia may provide beetles with a continual source of inocula during the extended egg-laying period.
We studied the effects of forest height and forest gap on assemblages of flying beetles in an American beech (Fagus grandifolia Ehrh. (Fagaceae) — sugar maple (Acer saccharum Marsh. (Aceraceae)) forest in Quebec. From June until August of 2005, beetles were collected in Lindgren funnel traps placed in the canopy (20–25 m height) and upper understorey (3–5 m height) in proximity to five forest gaps (15–30 m in diameter) (at the edge of the forest opening or within the closed-canopy forest). We collected 1852 beetles representing 38 families and 172 species. Based on rarefaction curves, species richness was significantly higher in the canopy than in the upper understorey. Nonmetric multidimensional scaling ordination revealed a change in species composition in relation to vertical stratification but not to the forest gaps. Our findings confirmed the importance of the vertical forest gradient to overall diversity of forest coleopterans.