Recognize and assess Marssonina apple blotch

Summary

Once the occurrence and severity of AB can be assessed, appropriate control measures can be taken.
Practical recommendations:
• First symptoms on leaves can be seen after the primary infection (April/May) (Fig. 1). However, the first clear symptoms are star-like lesions (formed by acervuli interlinked by mycelium) with surrounding areas turning chlorotic and leaf yellowing. occur later, from June onwards (Fig. 2). Symptoms on fruits can appear but are rare (Fig. 3). First infected leaves are usually found close to the trunk (Fig. 4).
• The disease is best assessed in August/September when symptoms are most visible (Fig. 5, 6) using the assessment scale in Table 1, found in the Practice Abstract.