Agriculture Reference
In-Depth Information
Fig 17.5 A severe bacterial spot infection on two varieties of plum.
well developed. Stem cankers are rarely larger than 1-2 cm,
but if numerous they may cause shoot distortion or dieback.
If allowed to progress unchecked, spring or summer
cankers that have formed on young trees can develop into
deep, scaffold branch cankers.
Fruit: typical fruit lesions on peach, nectarine and apricot
consist of tan, pinpoint spots that crack to form pits on the
surface. Cracks and pits may be quite extensive and are
often associated with a gummy exudate. On ripe fruit, a
green halo may surround the pits.
Fig 17.3 Limb dieback caused by bacterial spot.
Plums develop fewer, but larger, circular greasy spots that
darken and crack in the centre as the fruit grows.
Twigs and stems: twigs develop greasy, dark green,
elongated areas that develop into tan, sunken areas called
cankers, during spring and summer.
Small, greasy lesions appear on the rapidly growing
young branches in early spring. They become elongated,
depressed and tan. Cracks may form in the lesions and
develop into open cankers from which gum exudes. Cankers
may also develop during the summer after leaf symptoms are
Fig 17.4 Bacterial spot canker on a young shoot.
Fig 17.6 Lesion of bacterial spot on a mature, and a ripe, red plum.
