Just because the outbreak occurred on an organic farm... doesn't mean it was "caused by" the lack of pesticide use (or any other cultivation practices, per se). In fact, as to that particular outbreak, the very WP page you cite says:

Using epidemiological methods the outbreaks in 2011 were traced to a shipment of seeds from Egypt that arrived in Germany in December 2009.

Citing as a source:

http://phys.org/news/2012-02-insight-whole-genome-sequencing...