Cause:
Phomopsis viticola, a fungus. The disease has been found in vineyards west of the Cascades but has not been associated with much damage. The fungus overwinters in last year’s cane growth. Fruiting bodies of the fungus (pycnidia) develop in the periderm and produce many spores in the spring. These spores are exuded during rain events when the bark is wet. Spores are then rain splashed to developing shoots. Warm temperatures during long wet periods favor infection. About 10 hours of shoot wetness is required for light infections at 50° F. Young, rapidly growing tissues are most susceptible.
Symptoms:
In the dormant season, infected canes may become bleached, and numerous black fruiting bodies (pycnidia) may develop all along the cane’s basal region. This is the most common symptom in the Pacific Northwest; however, other non-pathogenic fungi can cause similar cane bleaching. Susceptible cultivars may show elongate lesions on the cane’s basal internodes. Small leaf spots also can occur early in leaf development, which can severely crinkle or misshape the leaf. Leaf petioles and cluster rachises also can develop lesions in severe years. Fruit rot has not been observed in the Pacific Northwest.
Notice the scars on the base of current-season cane (shoot).
Lesions look like little tears along the cane of this Chancellor grape.
Fruit rot is rarely seen in the PNW.
Cultural
control:
Remove infected canes during normal pruning operations in the dormant season.
Chemical
control: Spray when shoots are 0.5 to 1 inch long and again when shoots are 5 to 6 inches long. Application of lime sulfur prior to or at bud break was useful in combination with
in-season fungicides for control of this disease in Ohio.
Abound at 10 to 15.5 fl oz/A. Alternate with other fungicides. Do not apply more than four times a year for wine grapes (or 3 times a year for juice grapes), more than twice sequentially or within 14 days of harvest. Sprayers used to apply Abound should not be used on apples such as ‘Gala’, ‘Cox’s Orange Pippin’ and ‘McIntosh’. A group 11 fungicide. 4-hr reentry.
Captan 80 WDG at 2.5 lbs/A. Do not apply more than 24 lb/A/year. May be applied up to the day of harvest. Do not use with oils, lime or alkaline materials. 3 day reentry.
Flint 50 WG at 3 oz/A. Do not use on ‘Concord’ grapes. Rotate with other fungicides that have different modes of action. Do not apply more than twice consecutively, or more than six (6) applications total per season, or use more than 24 oz/A/season or use within 14 days of harvest. A group 11 fungicide. 12-hr reentry.
Mancozeb products such as Manzate 200 DF, Penncozeb 75 DF or Dithane DF at 1.5 to 2.5 lb/A. Do not apply within 66 days of harvest. Disease may be called "dead arm" on some labels. 24-hr reentry.
ManKocide at 2.6 lb/A. Do not apply within 66 days of har-vest. May injure copper-sensitive cultivars such as 'Concord'. 24-hr reentry.
Pristine at 8 to 12.5 oz/A. Do not use more than two (2) consecutive applications, within 14 days of harvest, or more than 5 times/year. Do not use on labrusca-type grapes such as Concord and Niagra due to possible foliar injury. A group 7 and 11 fungicide. 12-hr or 5-day reentry based on activity.
Sovran at 3.2 to 4.8 oz/A. Rotate with other fungicides that have different modes of action. Do not make more than 2 consecutive applications or within 14 days of harvest. A marginal burn may develop on young leaves if an organosilicone based adjuvant is used. Injury may occur to some sweet cherries, such as Van, if accidentally sprayed. A group 11 fungicide. 12-hr reentry.
Ziram 76 DF at 3 to 4 lb/A at 3 to 4 lb/100 gal water. 48-hr reentry.
References:
Erincik, O., Madden, L.V., Ferree, D.C., and Ellis, M.A. 2003. Temperature and wetness duration requirements for grape leaf and cane infection by Phomopsis viticola. Plant Disease 87:832-840.
Nita, M., Ellis, M. A., Wilson, L. L. and Madden, L. V. 2006.
Effects of Application of Fungicide During the Dormant Period on Phomopsis Cane and Leaf Spot of Grape Disease Intensity and Inoculum Production. Plant Disease 90:1195-1200.
Content edited by:
Jay W. Pscheidt on
January 1, 2009
