The relative importance of diseases on apple is varying with cultivar, management, time,
and climate. Many aspects of the cropping system influence the development of diseases.
The choice of the variety determines the disease management during the lifetime of the
orchard. Cultural practices improve the growth and nutrial status of the tree, and therewith
influence the susceptibility of the plant and fruits to diseases directly. Prolonged growth
can also have an indirect effect by causing a microclimate and growing pattern that
favours infection of tree, leafs and fruits by various diseases. Sanitation measures are
common practise for most organic fruit growers and help to make other measures more
effective by reducing infection inoculums. Despite all preventive measures, disease control
in organic orchards at an economically feasible level still largely depends on the
application of fungicides. Measures that allow reduction of fungicidal applications on key
diseases, lead to the development of a secondary disease complex that can cause severe
losses when not managed effectively and make a well thought-out control strategy
necessary.
In research, advisory and practical decision making, disease management in organic
orchards should always be seen in the perspective of the management of the total growing
system. With all factors that contribute to disease management in organic orchards
optimized, we are able to successfully implement new materials and methods that may not
be as effective as common fungicides in themselves, but add to the effectiveness of the
disease management system as a whole.
This total system approach makes organic fruit growing what it is
