Susceptibility to Apple Scab, Nectria Cancer and Powdery Mildew of Different Unsprayed Apple Varieties

Summary in the original language of the document

Twentyfive apple varieties were evaluated for Apple scab (Venturia inaqualis), Nectria
canker (Nectria galligena) and Powdery mildew (Podosphaera leucotricha) for 4 to 7 years.
The trees were grown unsprayed. The weather conditions at the experimental orchard
normally results in high infections of apple scab and low infections of powdery mildew.
Infections of Apple scab is often seen also in scab resistant varieties. Williams Pride,
Katinka and Katrina (scabresistant varieties) were the only varieties not showing scab in
the experimental period. The two scabresistant varieties Angold and Produkta (varieties
having a poor fruit quality) was unsusceptible to Nectria canker. The reference variety
Elstar/Elshof was in all plantings among the most resistant varieties. Powdery mildew is
not a problem at the experimental orchard. Most varieties had low susceptibility to
Powdery mildew. Varieties with low susceptibility to diseases in general were Angold,
Produkta, Rajka, Rubinola, Ahrista, Gerlinde, Gul Richard, Sukkertop, Katinka, Katrina,
Marian and Primicia.