Reducing russeting of organically grown Elstar to increase quality

Summary in the original language of the document

Sales organisations indicated that opportunities for organic apples sales can increase
when quality increases, in particular reducing the amount of russeting.
The use of copper is probably the most important factor for russeting. Therefore a worst
case scheme was compared with a scheme with reduced copper application. Furthermore,
there was a particular interest in the effects on russeting of potassium bicarbonate
(Armicarb) because this product might be an important element in a copper free fungicide
scheme. Application of Armicarb was investigated on wet or dry canopy and effects of two
different dosages were studied. All the schemes were compared with a worst case organic
fungicide scheme with copper. The experiment was done on two year old Elstar trees
because Elstar is the most important organically grown cultivar in the Netherlands. Effects
of the schedules on russet and scab control were evaluated. At harvest no effects were
found on scab. Between the different schemes with copper no differences were found in
amount of russet. Only the highest dosage of Armicarb (10 kg/ha) and the schedules with
Armicarb on a wet canopy gave more russet compared with the worst case scheme. Also
effects on fruit rot were evaluated.