Black spot of grapevines in Western Australia

Page last updated: Tuesday, 14 May 2019 - 1:11pm

Black spot, or anthracnose disease of grapevines is caused by the fungus Elsinoe ampelina. It is present in WA vineyards but has been successfully managed through the correct application of fungicides at the right time.

The disease occurs after rainfall in spring and infects young leaves and stems. If uncontrolled it can cause significant yield and quality loss. Damage to canes can also create issues when pruning vines in subsequent seasons.

Table grape varieties such as sultana and red globe are more susceptible to infection than wine grape varieties.

Background

Black spot or anthracnose of grapevines is caused by the fungus Elsinoe ampelina. The disease is found worldwide where grapes are grown, including Western Australia. It can be particularly damaging in regions that experience cool, wet springs and is often more of a problem for table grape varieties such as sultana and red globe. It can reduce fruit yield and quality.

The introduction of fungicides to prevent the disease has reduced its impact. In Western Australia, the disease can appear when spring rainfall occurs and control measures have not been used or have been used incorrectly.

Symptoms

The disease produces characteristic symptoms on leaves and shoots, particularly in the early stages of the growing season.

On leaves, small dark brown to black circular lesions appear after rain in the spring (Figure 1).

Grape leaf showing the small circular lesions which appear on young leaves early in spring
Figure 1 Small circular lesions on young grape leaves early in spring

Several leaves or shoots can be infected in a localised area, with the more severely infected leaves showing the greater number of leaf spots. Small lesions expand with the leaf and eventually the centre of the lesion falls out, leaving the leaf with a 'shot hole' appearance (Figure 2).

Grape leaf showing the ‘shot hole’ appearance of leaf lesions when the centre of the lesion falls out
Figure 2 ‘Shot hole’ appearance of leaf lesions when the centre of the lesion falls out

Infected leaves often have a distorted appearance (Figure 3).

Grape leaf showing distorted and crinkled appearance caused by black spot infection
Figure 3 Distorted and crinkled appearance caused by black spot infection

On shoots, infection is seen as small circular lesions with white to grey centres and a defined dark brown to black margin (Figure 4).

grape stem with blackspot infection
Figure 4 Small circular lesions on a stem with grey white centres and distinct black margin of the lesion

The centres of the lesions can appear flaky as the lesion ages (Figure 5).

Grape stem showing older lesions which have developed a flaky appearance
Figure 5 Older lesions develop a flaky appearance. The centre of the lesion may fall out leaving callused edges and a sunken appearance

Older lesions develop callused edges and the centre is sunken. This can occasionally be as deep as the middle of the shoot. Lesions may merge, creating several larger lesions on the stem (Figure 6).

Grape stem showing lesions which have coalesced to form one large lesion
Figure 6 Stem lesions may coalesce to form one large lesion (bottom of stem)

Severely infected shoots can have lesions that girdle the shoot which is likely to either break off during the season or produce no bunches at all. Loss of shoots reduces the number of viable canes or spurs in subsequent seasons.

Small brown spots appear on berries that enlarge to be purple black in colour and occasionally have grey to white centres.

Black spot of grapevines in Western Australia

Authors

Andrew Taylor
Colin Gordon

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