Alternative treatments for late blight control in organic potato: Antagonistic micro-organisms and compost extracts for activity against Phytophthora infestans.

Abstract

The effects of various fungi, bacteria and different compost extracts on foliar infection of<br>potato (Solarium tuberosum) with Phytophthora infestans were tested in detached leaf bioassays<br>in 2001-2003. Application of microorganism inocula and compost extracts as well as<br>copper oxychloride to excised leaves resulted in different degrees of blight control. In general,<br>suppression of blight lesion growth was not improved by applying the antagonists before<br>the leaves were inoculated with Phytophthora spores. There was some evidence that extracts<br>made from different compost feed stocks of different ages suppressed leaflet infection with<br>blight. However, results were very limited and inconsistent. Moreover, the effects were much<br>smaller than where copper oxychloride was used. Improved efficacy of acceptable alternatives<br>to copper fungicides especially in organic farming is required. No promising effective<br>alternative to the use of copper fungicides to reduce late blight infection in organic potato<br>production systems was identified in the experiments.