Germany: False mildew (Bremia lactucae) regularly causes loss of production in the cultivation of organic lettuce. Researchers of the Julius Kühn Institute therefore did a four-year long research project for alternative regulating possibilities, as announced by the German 'Bundesanstalt für Landwirtschaft und Ernährung' (BLE).
With the available mildew resistant varieties the cause of the sickness cannot be controlled for a long period. The reasons for this are the many different varieties formed by the cause of the sickness, which break through the existing resistances all the time. In the by BLE coordinated research project various scientists in cooperation with the association 'Kultursaat e.V.' mainly researched the endurance of so-called field resistant varieties and lines.
Contrary to the usual variety specific resistances of existing kinds the field resistance have the advantage that it, independent of the mildew variety, protects against an infection and therefore works on a wider basis. At the tests the field resistant lines, which were researched, offered by weak and average pressure of damage, sufficient protection against the cause of the sickness. This was especially the case with the lettuce varieties Batavia and iceberg lettuce. Field resistant cabbage lettuce lines were somewhat more susceptible. However, at severe effects the endurance, because of the field resistance, was insufficient with all of the three lettuce varieties.