Growth and sporulation of phytopathogenic microscopic fungi were studied under a static magnetic field. The applied flux densities were 0.1, 0.5, and 1 mT. The magnetic field decreased the growth of colonies by 10% using this flux density region. At 0.1 mT flux density, the deviations are significant, P =.001, while in other cases the deviations generally are not significant. At the same time, the number of the developed conidia of Alternaria alternata and Curvularia inaequalis increased by 68-133%, but the number of Fusarium oxysporum conidia decreased by 79-83%. The deviations are generally significant at the P =.05 level.
Since September 2002, Catalpa bignonioides trees heavily infected with powdery mildew have been observed in five localities in Hungary. Infections appeared and spread rapidly on both young and older Catalpa trees planted as ornamentals in parks and along the streets. White mycelia principally covered the upper surfaces of the broad Catalpa leaves but were also found on the lower surfaces. Both young and older leaves were infected. Sporulating powdery mildew colonies were also found on the fruits. Conidia were produced singly on the conidiophores and measured 22-35 × 8-15 µ m. Appressoria were simple or lobed, opposite or spread along the hyphae. Ascomata were produced in abundance on some leaves, mostly on the upper leaf surfaces. These measured 96 -128 µ m in diameter and bore five to nine 115 -420-µ m-long appendages. The appendages terminated in dichotomously branched, knob-like or slightly recurved tips. The ascomata contained four to seven stalked or sessile asci. Based on these characteristics, the pathogen was identified as Erysiphe elevata (syn. Microsphaera elevata ). It clearly differed from E. catalpae , a species described from Armenia (Simonian, 1984) and also reported from some European countries (Braun, 1995). Pathogenicity was confirmed in a test conducted as described in Szentiványi et al . (2004) for snowberry powdery mildew. Erysiphe elevata is a common powdery mildew species infecting Catalpa spp. trees in North America (Braun, 1987), but its occurrence has not been reported outside the USA and Canada to date.
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