DEVELOPMENT OF HELMINTHOSPORIUM SOLANI IN RESPONSE TO TEMPERATURE AND CONDENSATION ON STORED POTATO CROPS
RC CLAYTON, C HARDY and RT PRINGLE
Scottish Agricultural College, Craibstone Estate, Bucksburn, Aberdeen AB21 9YA, UK
Background and objectives Silver scurf, caused by Helminthosporium solani has a significant effect on the visual quality of potatoes, particularly those for sale in pre-pack or seed markets. Pressures to reduce fungicide use in production have resulted in only two key methods for disease control in store being available, namely manipulation of temperature and free surface moisture. This study provides data on infection and disease development for incorporation into computer-driven store management systems.
Materials and methods
Results and conclusions
Observation of spores inoculated onto healthy tubers showed that more than 60% of spores germinated within 2 ;h in the presence of free moisture. There appeared to be no tropic control of germ tubes and only 14% made contact with the potato epidermis. Of those, only half penetrated the epidermis and produced new lesions. Penetration occurred within the first 6 ;h of free surface moisture and the frequency did not increase thereafter. The frequency of penetration correlated highly with the number of infection sites per tuber assessed visually after long term storage.
These studies have demonstrated the need to limit condensation and free surface moisture during potato storage, particularly after store loading where higher temperatures are required for wound healing. In concurrent studies, algorithms were developed to control condensation in potato stores and have been successfully incorporated into computerized store-management systems.