Anthracnose
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Beginner
Scientific Name
Elsinoe ampelina
Identification
Leaves:
- Initially pin-prick dark spots
- Developing into small round spots with brown or black margins with greyish-white centres which drop out causing a ‘shot-hole’ appearance
- Severe infections cause malformed leaves that shrivel up and drop
Shoots:
- Deep elongated cankers
- Greyish in the centre with a raised dark reddish brown to violet-black edge
- Infected shoots crack and become brittle
- Lesions on the rachis and pedicels similar to those on shoots
Berries:
- Small (6 mm diameter)
- Reddish circular spots becoming violet with a greyish centre and a raised black edge “bird’s eye rot”
- Lesions can extend into the pulp, causing cracking and opening the berry to secondary infections
- Severely infected berries dry up and drop prematurely
Often Confused With
Hail injury --no raised black edges, generally only on windward side of vines
Pesticide Spray injury – no raised black edges
Black rot – lesions on fruit are brown then black with pycnidia; infected mummified berries remain attached to the rachis; lesions on leaves are dark brown with a bronze-grey centre with pycnidia;
Phomopsis – razor-blade slash on shoots; does not extend as deeply into the shoot
Period of Activity
Particularly from stage 1st leaf unfolded to stage 4-6 leaves unfolded and inflorescences visible. Rapidly expanding leaves are most susceptible. Fully expanded leaves are immune to infection. Leaves infected early in the season stop producing conidia by summer but recently infected leaves and cankers on shoots continue to sporulate. Berries are susceptible until about 4 weeks post bloom.
Scouting Notes
Monitor from 3-5 leaves until harvest, particularly after rainfall and storms, when the vines are wet for more than 12 hours. Look for for the presence of small black spots, particularly on young leaves. Closer to harvest, look for “birds eye rot” on the berries.
Threshold
There is no threshold
for initiating anthracnose control. Fungicides should be applied before
infection occurs.
Advanced
Scientific Name
Elsinoe ampelina
Identification
Leaves:
- Initially pin-prick dark spots
- Developing into small round spots with brown or black margins with greyish-white centres which drop out causing a ‘shot-hole’ appearance
- Severe infections cause malformed leaves that shrivel up and drop
Shoots:
- Deep elongated cankers
- Greyish in the centre with a raised dark reddish brown to violet-black edge
- Infected shoots crack and become brittle
- Lesions on the rachis and pedicels similar to those on shoots
Berries:
- Small (6 mm diameter)
- Reddish circular spots becoming violet with a greyish centre and a raised black edge “bird’s eye rot”
- Lesions can extend into the pulp, causing cracking and opening the berry to secondary infections
- Severely infected berries dry up and drop prematurely
Often Confused With
Hail injury --no raised black edges, generally only on windward side of vines
Pesticide Spray injury – no raised black edges
Black rot – lesions on fruit are brown then black with pycnidia; infected mummified berries remain attached to the rachis; lesions on leaves are dark brown with a bronze-grey centre with pycnidia
Phomopsis – razor-blade slash on shoots; does not extend as deeply into the shoot
Biology
The pathogen probably overwinters in cankers formed on the canes and in infected berries on the ground and left in the trellis. In the spring, acervuli form and produce conidia that are dispersed by rain or irrigation of 2 mm or more. Spores can spread as far as 7 m from an infected vine. The disease develops at temperatures of 10- 35°C with maximum development at 20-26°C. Infection can occur with as little as 3 hr of wetness at 21º C. Longer wetness periods result in more severe infection. Pinpoint lesions develop on young expanding leaves 6-9 days after infection and are capable of producing secondary spores the day afterward. Maximum sporulation on lesions on leaves occurs when the lesion is 1 mm in diameter. Pinpoint spots develop on young berries 3 days after infection while those on older berries develop after 8 days. Once berries reach 5-7° Brix, they are highly resistant to infection. The rachis can be infected until 8 weeks post-bloom. Anthracnose is most commonly seen in hybrids as opposed to vinifera in Ontario.
Period of Activity
Particularly from stage 1st leaf unfolded to stage 4-6 leaves unfolded and inflorescences visible. Rapidly expanding leaves are most susceptible. Fully expanded leaves are immune to infection. Leaves infected early in the season stop producing conidia by summer but recently infected leaves and cankers on shoots continue to sporulate. Berries are susceptible until about 4 weeks post bloom.
Scouting Notes
Monitor from 3-5 leaves until harvest, particularly after rainfall and storms, when the vines are wet for more than 12 hours. Look for for the presence of small black spots, particularly on young leaves. Closer to harvest, look for “birds eye rot” on the berries.
Threshold
There is no threshold for initiating anthracnose control. Fungicides should be applied before infection occurs.
Management Notes
Selection of a site with good air drainage,north-south orientation of the rows to maximize sun exposure, and practices that open the canopy so that air circulation and spray coverage are improved can help control of black rot.
Pruning, training and leaf-removal will reduce shading and allow rapid air movement can reduce the frequency and duration of periods of high humidity which favour the disease. Infected clusters and shoots should be removed from the canopy as soon as possible after harvest and either dropped to the ground and buried or removed and burned outside the vineyard. Do not keep them in a pile beside the vineyard without burning as spores can blow into the vineyard in the spring. Retain only healthy, lesion-free canes.
Good weed control and proper soil drainage will reduce relative humidity and the amount of free moisture which may increase the spread of the fungus.
Management with fungicides – Dormant sulphur applications for powdery mildew control and some fungicides applied for other diseases during the season will have the added benefit of protecting tissues from infection by anthracnose. See OMAFRA Publication 360, Guide to Fruit Production - Chapter 5 Grapes (PDF)..
Different cultivars all have different susceptibilities to diseases. See Table 5-5 Relative Susceptibility of Grape Cultivars to Diseases.
Fungicides have different modes of action, and differ in their activity on grape diseases. See Table 5-6 Activity of fungicides on grape diseases.
