Phomopsis viticola: prohibited disease

When am I likely to see it?

Phomopsis cane and leaf spot is most visible early in the season after budburst but prior to full canopy development obscuring leaf and lower cane tissue. Leaf lesions are the most obvious initial symptom.

Infection can occur at a range of temperatures but is optimal at 23°C with infection favoured by successive periods of wet weather and high humidity in spring. It can take three to four weeks from the infection event until symptoms are visible in the vineyard.

Can be confused with

Symptoms of Phomopsis cane and leaf spot may be confused with other fungal diseases and damage caused by other agents, such as frost, which cause stems to bleach. A related fungus, Diaporthe australafricana, that is present in WA can produce bleached canes with black fruiting bodies (Figure 6).

Figure 6 Bleached canes can be caused by several factors in the vineyard including Diaporthe australafricana

Grapevine black spot (anthracnose) infections caused by Elsinoë ampelina can also produce leaf and stem symptoms. Grapevine black spot produces black leaf spots but these are not associated with yellow halos and enlarge with age with the centres falling out (Figure 7).

Cane infection of black spot differs to that of P. viticola in that they are usually more circular in appearance with a whitish centre surrounded by a black margin (Figure 8) as detailed in Black spot of grapevines in Western Australia.

Figure 7 With black spot leaf infection the small black spots enlarge and the centre falls out of the infected area

Cane infections of black spot differ from P. viticola in that they are usually more circular in appearance with a whitish centre surrounded by a black margin (Figure 8).

Figure 8 Black spot cane infection showing circular white lesions with a dark margin

Berry rot may be confused with infection caused by Botryosphaeria species. See Know your grapevine bunch rots.

Applications of contact herbicides can cause small spots on leaves where the contact has occurred. The spot will initially appear yellow but progress to black as the herbicide kills the leaf tissue (Figure 9).

The spots are often larger than those caused by P. viticola. Spray damage is likely to occur over a larger area of the vineyard rather than localised infection caused by P. viticola and will include all leaf material on the vine.

Figure 9 Contact herbicide spray damage initially appears as yellow spots but develops into dead tissue as the herbicide kills the leaf area contacted

These spots are larger than those caused by P. viticola. Spray damage is likely to occur over a larger area of the vineyard than a localised P. viticola infection and will include all leaf material on the vine as the herbicide kills the leaf tissue.

Spread

Spores of P. viticola are dispersed within the vineyard by rain splash and spread is generally localised. Infection comes from spores located within the fruiting bodies on canes or spurs that were diseased in the previous season.

Long distance dispersal of the disease occurs through the movement of infected or contaminated propagation materials such as budwood, cane cuttings and nursery stock. Phomopsis viticola has also been reported to be spread by pruning equipment and agricultural machinery.

What to do if infection suspected

Phomopsis viticola is a prohibited organism for WA. It is important that suspect infestations are reported. Please contact the Pest and Disease Information Service (PaDIS) using the contact details at the bottom of this page. You can also send photos of suspect symptoms using MyPestGuide.