Lygus Hahn (Hemiptera: Miridae) are serious pests of economically important field, fruit, vegetable, and greenhouse crops in Canada. The release of European Peristenus Förster (Hymenoptera: Braconidae) in the USA has resulted in significant suppression of this pest and has renewed interest in the release of European Peristenus spp. in Canada. Prior to the release of exotic Peristenus spp., ecological host range studies need to be conducted to define their habitat and host associations. <p>These associations can be difficult to study using conventional methods. Morphological similarity of related parasitoids prevents species-level identification by dissection. Host rearing is time-consuming and can result in high levels of host and parasitoid mortality. To facilitate identification of immature Peristenus spp. in their hosts, a multiplex PCR assay was developed. This assay provided a specific and sensitive tool to screen individual insects for three parasitoid species simultaneously. <p>To validate the utility of the multiplex PCR assay in ecological host range studies, parasitism and parasitoid species composition obtained using conventional and molecular techniques were compared. Molecular methods compared favorably with conventional methods; however, more complete species composition information was available with the multiplex assay. To improve the quality of risk assessment studies and extract the most accurate ecological host range data, molecular methods were used to evaluate host-parasitoid associations in mirid populations collected in two ecoregions. Several new host-parasitoid associations were recorded for <i>P. digoneutis</i> and <i>P. relictus</i>, but parasitism of non-target mirids was low. <p>Parasitism of the target host collected from different plant species was evaluated to help clarify Peristenus host-plant associations. Despite the investigation of three different host plant species, no difference was observed in the parasitism level or parasitoid species composition in <i>L. rugulipennis</i>. The post-release utility of the multiplex assay was investigated in Canada, where Lygus parasitoids may have dispersed following release in the USA. To confirm establishment, samples were analyzed using the multiplex PCR assay, and P. digoneutis was detected for the first time in southern Ontario.

Lygus Hahn (Hemiptera: Miridae) are serious pests of economically important field, fruit, vegetable, and greenhouse crops in Canada. The release of European Peristenus Förster (Hymenoptera: Braconidae) in the USA has resulted in significant suppression of this pest and has renewed interest in the release of European Peristenus spp. in Canada. Prior to the release of exotic Peristenus spp., ecological host range studies need to be conducted to define their habitat and host associations. <p>These associations can be difficult to study using conventional methods. Morphological similarity of related parasitoids prevents species-level identification by dissection. Host rearing is time-consuming and can result in high levels of host and parasitoid mortality. To facilitate identification of immature Peristenus spp. in their hosts, a multiplex PCR assay was developed. This assay provided a specific and sensitive tool to screen individual insects for three parasitoid species simultaneously. <p>To validate the utility of the multiplex PCR assay in ecological host range studies, parasitism and parasitoid species composition obtained using conventional and molecular techniques were compared. Molecular methods compared favorably with conventional methods; however, more complete species composition information was available with the multiplex assay. To improve the quality of risk assessment studies and extract the most accurate ecological host range data, molecular methods were used to evaluate host-parasitoid associations in mirid populations collected in two ecoregions. Several new host-parasitoid associations were recorded for <i>P. digoneutis</i> and <i>P. relictus</i>, but parasitism of non-target mirids was low. <p>Parasitism of the target host collected from different plant species was evaluated to help clarify Peristenus host-plant associations. Despite the investigation of three different host plant species, no difference was observed in the parasitism level or parasitoid species composition in <i>L. rugulipennis</i>. The post-release utility of the multiplex assay was investigated in Canada, where Lygus parasitoids may have dispersed following release in the USA. To confirm establishment, samples were analyzed using the multiplex PCR assay, and P. digoneutis was detected for the first time in southern Ontario.

Thesis (Ph. D.)--Brigham Young University. Dept. of Integrative Biology, 2003. / Includes bibliographical references.

No description available.

No description available.

Pseudomonas chlororaphis (aureofaciens) 30-84 is a biocontrol bacterium effective against take-all disease of wheat. Phenazine (PZ) production by strain 30-84 is the primary mechanism responsible for pathogen inhibition and the rhizosphere persistence of 30-84. The PhzR/PhzI system of strain 30-84 directly regulates PZ production and mutations in this QS system are defective in biofilm formation. Genetic complementation or direct addition of AHL signal restored biofilm formation to a phzI mutant. Mutations in PZ biosynthesis were equally defective in biofilm formation. Addition of PZ or genetic complementation of the PZ biosynthetic mutation restored biofilm formation. QS and PZ production also were involved in the establishment of populations on wheat seeds and plant roots. Presence of 10% wild type strain 30-84 in mixtures with QS or PZ mutants restored root colonization. These data demonstrate that QS and specifically PZ production are essential for biofilm formation by strain 30-84. This is a new role for PZs in the rhizosphere community.Strain 30-84 produces primarily phenazine-1-carboxylic acid (PCA) and 2-hydroxy-PCA (2-OH-PCA). We generated derivatives of strain 30-84 that produced the same total amount of PZs as the wild type but produced only PCA, or more efficiently converted PCA to 2-OH-PCA. These derivatives with altered PZ ratios differed from the wild type in initial attachment, biofilm architecture, and dispersal. Increased 2-OH-PCA production increased initial attachment, although both alterations resulted in thicker biofilms and reduced dispersal rates. Loss of 2-OH-PCA production resulted in a significant reduction in pathogen inhibition. My findings indicate that alterations in the endogenous ratios of PZs have wide-ranging effects on the biology of strain 30-84. I initiated studies to understand the mechanisms by which PZs affect surface attachment and biofilm development. Addition of PZs to metabolically inactivated cells improved adhesion compared to the inactive cells alone, suggesting that PZs may improve initial binding to surfaces. Results from whole genome transcription profiles of wild type strain 30-84 to a PZ mutant indicate that genes potentially involved in biofilm formation were up-regulated in the presence of PZs. These results provide initial evidence that PZs may modulate cell adhesion and biofilm formation via multiple mechanisms.

Two European leaf-eating beetles, Galerucella calmariensis L. and G. pusilla (Duft.)(Chrysomelidae:Coleoptera) were released at four sites in Quebec to manage the semi-aquatic exotic weed, purple loosestrife (Lythrum salicaria L.). Protocols for monitoring the Galerucella populations and detecting changes in the plant communities were implemented. In addition, the effect of seeding with native plants species in conjunction with Galerucella herbivory was tested in an experiment at a purple loosestrife stand in Ontario. Releases of lab-reared beetles in Quebec in 1996 did not survive to 1997 at any of the 4 sites, but releases of field collected beetles in 1997 overwintered successfully at 3 of the 4 sites. The density of purple loosestrife in 1998 ranged from 28% (Cap Tourmente) to 84% (Hull). The density of Galerucella in 1998 ranged from 6 (Lac St Francois) to 50 (Hull) adults/m 2/min. In the Ontario experiment, herbivory and seeding together interacted to increase the biomass of other plant species significantly---and thereby reduced the dominance (proportion of the biomass) of purple loosestrife---but did not have a significant effect on the biomass of purple loosestrife in the first season.

Field and controlled environment experiments were performed to assess the preemergence activity of the fungal pathogen, Phomopsis convolvulus Ormeno to control Convolvulus arvensis L. (field bindweed). A granular barley formulation of the fungal inoculum applied onto the field soil surface resulted in dramatic aboveground biomass reductions of both C. arvensis seedlings (94--100%) and regrowth from established plants (53--98%). Under field conditions, surface applications of the granular formulation resulted in greater biomass reductions (93--100%) compared with soil incorporation of the granules (31--97%). Rate of soil applied granules of P. convolvulus did not affect the level of weed control and 90--100% C. arvensis biomass reductions were obtained for all rates used (30 g, 20 g, and 10 g 0.25m--2 plot). The use of two different planting substrates in controlled environment studies led to major differences in C. arvensis disease development. With an inoculum application on the day of sowing, 81% mortality was obtained for seedlings grown in a sandy loam field sod compared with 50% of seedlings grown in a prepared peat moss medium. The susceptibility of C. arvensis biotypes from various geographic locations to P. convolvulus was similar following post-emergence, foliar inoculum applications. Significant above-ground (65--100%) and new root growth (56--72%) biomass reductions of established plants were obtained for two selected biotypes (Greece, USA-Montana) subjected to a preemergence granular inoculum application. In the presence of spring wheat (Triticum aestivum L.), field efficacy of P. convolvulus was enhanced and aboveground biomass of inoculated C. arvensis plants was reduced by 98% compared with inoculated C. arvensis plants grown in pure stand.

Cercariae of the digenean Plagiorchis noblei penetrate and kill a variety of aquatic larval dipterans. The present study determined whether these parasites can infect blackfly larvae, and established what biotic and abiotic factors affect parasite acquisition and the survival of infected hosts in the laboratory. Four species of blackfly larvae, Prosimulium mixtum, Simulium vittatum, S. decorum, and Stegopterna mutata, were exposed to cercariae in flowing water. Prevalence and intensity of infection of all species varied directly with exposure intensity and decreased with increasing water velocity, prevalence increased with larval size. Infection levels were higher for P. mixtum. The production of silk strands by the blackfly larvae and their persistence at low water velocities may facilitate parasite acquisition. Mortality among infected larvae of all species was three times that of controls. The data suggest that exposure to P. noblei cercariae adversely affected the survival of blackfly larvae.

No description available.