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Fusarium root rot (Fusarium spp.) is one of the most important seedling diseases of coneflower (Echinacea spp.) in Alberta greenhouses. Effects of microbial antagonists (Trichoderma spp.) and fungicides, including difenoconazole, fludioxonil, and a mixture of fludioxonil, metalaxyl and difenoconazole, on the management of this disease, were investigated in Alberta. Twenty Trichoderma isolates demonstrated antagonistic activity to Fusarium in agar plate bioassays, with inhibition rates ranging from 44 to 65%. Some Trichoderma isolates significantly ( p < 0.05) reduced disease incidence and severity on seedlings in greenhouse experiments. An in vitro bioassay indicated that difenoconazole and the mixture equally inhibited the growth of both Fusarium and Trichoderma, but, while fludioxonil strongly inhibited the growth of Fusarium, it had little effect on Trichoderma, according to the dose--response models developed ( p < 0.01, R2= 0.902-0.998). Two Trichoderma isolates, T1 and T13 were applied singly or in combination with a low rate of fludioxonil in greenhouse evaluations. The results suggested that fludioxonil and Trichoderma could be integrated into a disease management program for fusarium root rot in coneflower.

The metabolite produced by Mycosphaerella pinodes, the causal agent of mycosphaerella blight on field peas, was detected by thin layer chromatography (TLC) and was analyzed for its chemical and pathogenic characteristics. One blue dot was detected using 254nm UV light on TLC plate, and a spray of rho-anisaldehyde (110 degrees C, 30 min) also produced a blue dot. The solvent systems used for TLC analysis were ethyl acetate/water/acetone (5/2/5), chloroform/methanol/glacial acetic acid (19/10/2), toluene/ethyl acetate/90% formic acid (6/3/1), diethylether/methanol/water/90% formic acid (95/4/1/1), and bezene/methanol/acetic acid (24/2/1), with R(f) values (min-max) of 0.09-0.18, 0.88-0.95, 0.06-0.15, 0.39-0.47 and 0.05-0.12, respectively. The recovered metabolite from the TLC plate displayed UV absorption peaks at 212, 244, 250, 256 and 261 nm. The proposed formula of the main component of the metabolite was C16H12N3O6. The TLC-purified metabolite induced symptom of discoloration on detached pea leaves.

The potential for widespreadand severe infection makes ascochyta blight,seedling blight, and root rots major hindrancesto pea production in Alberta, Canada. Over 300bacterial strains were isolated from pea seedand soil samples taken from pea fields. Thesestrains were investigated for their biologicalcontrol potential against four fungal pathogens(Pythium ultimum, Rhizoctoniasolani, Fusarium avenaceum and Ascochyta pisi) of field pea in vitro. Selected bacterial strains were furtherevaluated in vivo. In an initial agarplate bioassay, 30 strains exhibitedantagonistic properties against the fourpathogens, with inhibition zones ranging from 5to 25 mm. Thirteen of these strains, allisolated from soil, inhibited only one or twoof the pathogens, while the remainingseventeen, including nine strains isolated frompea seeds, inhibited either three or all fourpathogens. In a more stringent bioassay, eightof the thirty strains failed to demonstrate theantagonistic features shown in the initialbioassay. Eight strains inhibited only onepathogen, six inhibited two, four inhibitedthree, and four strains inhibited all fourpathogens tested. Two strains ofPseudomonas fluorescens, five strains of Serratia spp. and two strains of Bacillus spp. were further evaluated ingreenhouse experiments. Five of the isolatesreduced the severity of diseases caused byPythium or Ascochyta, two isolatesreduced the severity of Rhizoctonia andone reduced the severity of Fusarium.

The host range of Ustilago bullata includes important forage crop and grassy weed species that germinate and establish under a wide range of temperature and salinity conditions. Previously, two subgroups (pathotypes 1 and 2) were identified from collections across the prairies, which had no host species in common. When germination of teliospores from these collections was assessed, the two pathotypes differed substantially in the stage of development reached at 20 h of incubation. This study was initiated to determine if differences between the pathotypes were consistent and if they corresponded with factors affecting the host environment during seed germination and establishment. Individual teliospores from representative collections of each pathotype were monitored throughout the germination process over a 16-h period. Teliospores of pathotype 1 initiated germination much more quickly than those of pathotype 2, but the time required for metabasidial development and sporidial doubling was similar for bot...

La production de brome des pres (Bromus riparius), graminee fourragere recemment introduite, connait un essor rapide dans les prairies canadiennes. Une etude a ete entreprise afin d'examiner l'effet du charbon des inflorescences (Ustilago bullata) sur cette nouvelle culture. U. bullata etait present dans plus de 60 % des champs de semences de brome des pres echantillonnes en Saskatchewan et en Alberta. Il se retrouvait frequemment la ou des especes de graminees sensibles etaient dominantes, soit dans 65 % des sites domines par le brome des toits (B. tectorum) ou l'orge agreable (Hordeum jubatum), dans 45 % de ceux domines par le brome japonais (B. japonicus), mais dans seulement 5 % de ceux ou predominait l'agropyre a chaumes rudes (Elymus trachycaulus). Il n'a pas ete trouve sur l'agropyre a crete (Agropryon cristatum) ni sur le brome inerme (B. inermis). L'incidence du charbon des inflorescences etait generalement faible, mais a un site, 95 % des plants de brome des toits etaient infectes et a de nombreux sites, plusieurs especes hotes etaient presentes, mais une seule etait infectee. Ces resultats semblent indiquer la presence de plusieurs pathotypes dans la region. Le traitement des semences a l'aide des fongicides carbathiine, captane, thirame, propiconazole et hexaconazole a permis, dans chaque cas, de livrer une lutte efficace contre le charbon des inflorescences lors d'essais en serre et au champ, sans observer de symptomes de phytotoxicite. L'entreposage de spores de charbon et de semences infectees jusqu'a un an a des temperatures allant de -7 a 36°C n'a pas influe sur le taux de survie et de germination des spores de charbon ni sur l'incidence du charbon chez les plantes cultivees a partir de la graine. Les plantes frappees par le charbon ont ete plus souvent victimes de l'hiver que les plantes saines une annee sur trois, et ont montre un affaiblissement de l'incidence et de la gravite des symptomes deux annees sur trois.