Effects of Rootstock and Budding Height on Bacterial Canker in French Prune.

Bacterial canker is one of the most economically important diseases of stone fruit trees, including 'French' prune (Prunus domestica). Field trials were conducted to evaluate the effect of rootstock selection and budding height on the incidence and severity of bacterial canker in four orchards with low to high disease pressure. Treatments included French prune scions low-grafted on 'Lovell' peach (Prunus persica) rootstocks as well as Myrobalan 29C (Prunus cerasifera) plum rootstocks grafted at 15, 50, and 90 cm above the rootstock crown. Another treatment consisted of growing Myrobalan 29C plum rootstocks in the field for one growing season, then field-grafting French prune buds onto rootstock scaffolds. Lovell peach rootstock provided the greatest protection from bacterial canker as measured by disease incidence and tree mortality in all orchards. Field-budded rootstocks and rootstocks grafted at the highest budding height provided moderate levels of resistance to bacterial canker. These treatments reduced the incidence but not the severity of disease.