Seasonal occurrence of the potato gangrene pathogen, Phoma exigua var. foveata, in the open air

Abstract

SUMMARYUsing a Casella High Volume Bacterial Sampler air samples were collected down wind of potato fields in central Scotland when it was raining and when it was dry between December 1978 and October 1982. Airborne propagules of Phoma exigua var. foveata were recovered from the open air during rainfall in most months of the year but the frequency of recovery was greatest in September, October and November. The numbers of colonies of P. exigua var. foveata detected during rainfall were much greater in September and October than during the rest of the year. Low numbers of colonies of P. exigua var. foveata were recovered in the absence of rainfall and their occurrence appeared to be associated with strong winds and dry soil conditions. These latter airborne propagules were detected during all the months except November to February when few samples were made. Sampling simultaneously up wind and down wind of potato fields in September and October demonstrated that the potato crop was the main source of airborne propagules caught down wind but small numbers of P. exigua var. foveata were recovered up wind in four out of the seven experiments.