The Erwinia bacterium seems to have become more aggressive in recent years and causes more damage in infested potato plants. This is the conclusion of researcher Jan van der Wolf of Plant Research International (PRI), part of Wageningen UR. He talked about his findings during the general meeting of the Arable Farming study group of the LLTB on 19 February in Baexem.
Photograph: Blackleg of potato caused by Dickeya spp. (Erwinia chrysanthemi)
PRI found that three types of the Erwinia bacterium cause damage in the Netherlands. These are Erwinia carotovora subsp. atroseptica, Erwinia chrysanthemi and Erwinia carotovora subsp. carotovora. Through to 2001 the three types were about evenly spread over the Netherlands; a shift was observed after that. In 2003 all infestations were found to be caused by the variant of Erwinia chrysanthemi. This variant also caused the largest part of the infestations in 2005.
Erwinia chrysanthemi develops better at higher temperatures than the other types. The higher temperatures of recent years may have had a positive effect on the survival of this bacterium. According to researcher Van der Wolf, potato growers can hardly prevent the introduction of Erwinia into their fields. Latent infestations are hard to detect. And pesticides to control the bacterium are neither available. The bacterium develops rapidly in potato tissue. And there are many host plants for Erwinia such as flower bulbs, onions, cabbage, chicory and a number of ornamental plants.
source:www.agd.nl