Diplodia seriata, cause of black fruit rot in organically grown apples in Holland, Belgium and Northern Germany

Summary in the original language of the document

A fruit rot resembling Gloeosporium infections but appearing on fruits prior to harvest was
noticed in organic apple orchards in Holland, Belgium and Northern Germany in 2007.
Infections were most commonly observed on ‘Elstar’, but other cultivars were also
affected. Fruit colonisation progressed in two steps, whereby a latent stage of sunken
black lesions in immature fruits gave rise to a rapidly spreading firm brown rot upon fruit
ripening. Isolation experiments from both stages consistently yielded a single species of
fungus identified as Diplodia seriata, formerly known under the teleomorph name
Botryosphaeria obtusa. Lesions of D. seriata were also seen on leaves as necrotic light
brown spots surrounded by a purple halo, and occasionally on small twigs as cankers.
Fruit mummies on apple twigs were heavily colonised by D. seriata and are thus likely to
carry inoculum for fruit infections during late summer or in the following growing season.