Cause:
Septoria rubi, a fungus that affects trailing berries such as 'Marion' and 'Santiam' blackberries, 'Boysenberry', and 'Loganberry'. Minute, black, fruiting bodies (pycnidia) are formed within infected tissue, mature, and produce spores. Rain spreads spores. In winter, the sexual spore stage forms on old dead leaves and on infected canes. During the wet early spring, more spores are produced, and these cause many new infections.
Symptoms:
Leaf spots vary from light to dark brown. At first they are about 0.12 inch in diameter and purplish in color. They later turn brown. In older leaf spots, centers are whitish with brown to red borders. Infections on canes are similar to those on leaves but are generally inconspicuous. During wet seasons in Oregon, a brown fruit rot has been found on 'Loganberry'. Blackberry rust may look similar on the upper surface of a leaf but has yellowish pustules in the same location on the underside of a leaf.
Note the small red leaf spots with gray centers on these boysenberry leaves.
Leaf and cane spot lesions on canes.
In older leaf spots, the centers are whitish with brown to red borders.
Cultural
control:
Alternate-year (AY) fruiting program. The disease has not been a problem in AY-producing fields if canes are trained to the trellis as they grow. If canes are allowed to lie on the ground, leaf and cane spot can be just as severe as in fields where berries are harvested annually.
Remove old fruiting canes after harvest.
Trellis canes in August through early September or wait until late winter (February or March). Canes trained after early September may be more susceptible to winter injury.
Control weeds because they can provide a natural "moist chamber" for infection and prevent effective spray coverage.
Chemical
control:
For every year (EY) producers, spray after harvest.
Fixed coppers such as Kocide, Nu-Cop, or C-O-C-S with a 24-hr reentry or Cuprofix, Nordox or Copper-Count-N with a 12-hr reentry.
Lime sulfur at 2 gal/100 gal water Polysul, Lily Miller Dormant Spray for Disease and Bonide Lime Sulfur Spray are registered for home use. 48-hr reentry.
Spray again in early October before heavy rains begin.
Bordeaux 8-8-100.
Fixed coppers such as Kocide,
Nu-Cop, or C-O-C-S with a 24-hr reentry or Cuprofix, Nordox or Copper-Count-N with a 12-hr reentry.
Spray again at budbreak in early March.
a. Lime sulfur at 8 gal/100 gal water. May burn leaves when shoots are 0.75 inch or longer. Polysul, Lily Miller Dormant Spray for Disease and Bonide Lime Sulfur Spray are registered for home use. 48-hr reentry.
Fixed coppers such as Kocide,
Nu-Cop, or C-O-C-S with a 24-hr reentry or Cuprofix, Nordox or Copper-Count-N with a 12-hr reentry.
Sulforix at 3 gal/100 gal water. Apply as a delayed dormant spray. 48-hr reentry.
Spray young primocanes at 0 to 6 inches growth, 12- to
18-inch growth and 2- to 3-foot growth.
Abound at 6 to 15.5 fl oz/A. Do not apply more than 2 sequential applications or more than three (3) applications per year. May be applied on the day of harvest. 4-hr reentry.
Cabrio EG at 14 oz/A. Do not use more than two (2)
sequential applications or more than four (4) applications per year. May be used on day of harvest. 24-hr reentry.
Captan 80 WDG at 2.5 lb/A. Do not apply within 3 days of harvest. 72-hr reentry.
Fixed copper (such as Kocide, Nu-Cop or C-O-C-S). 24-hr reentry.
Pristine at 18.5 to 23 oz/A. Do not use more than 2 consecutive applications or more than 4 times/year. Can be used day of harvest. 12-hr reentry.
Propiconazole-based fungicides are registered. Do not use more than 30 fl oz/A/season or within 30 days of harvest.
Orbit at 6 fl oz/A. 12-hr reentry.
PropiMax EC at 6 fl oz/A. 24-hr reentry
Tilt at 6 fl oz/A. 12-hr reentry.
Content edited by:
Jay W. Pscheidt on
January 1, 2009
