APS Abstracts of Presentations

Influence of environment on atmospheric concentrations of Peronospora antirrhini conidia in field-grown snapdragons. J. M. Byrne, M. K. Hausbeck, and L. E. SCONYERS. Michigan State University, East Lansing, MI. Phytopathology 94:S13. Publication no. P-2004-0080-AMA.

Atmospheric concentrations of Peronospora antirrhini conidia in a commercial snapdragon field were monitored using a Burkard spore sampler over three growing seasons to investigate the influences of environment on the concentration of airborne conidia. Atmospheric conidial concentrations followed a diurnal pattern, and peak conidial concentrations occurred between 0700 and 0900 hours. Minimum daily temperatures below 10.0°C appeared to have a moderate limiting effect on atmospheric conidia concentrations, while temperatures below 6.0°C had more severe limiting effects. Maximum daily temperatures higher than 30.0°C limited concentrations of atmospheric conidia. Long dew periods (>6 hours) were associated with relatively large conidia releases. Consecutive days with short leaf wetness periods suppressed atmospheric conidial concentrations. Significant positive correlations were found between total rainfall and total spore count in 2000, which may explain large spore concentrations for that year. These findings, combined with current management practices, can aid in reducing downy mildew.

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