Phomopsis viticola: prohibited disease

Symptoms

In spring, small dark spots (about 1mm in diameter) surrounded by yellow halos develop on the leaves (Figures 1).

Figure 1a Leaf infection of Phomopsis viticola in a New York state vineyard 

Figure 1b Leaf severely infected by Phomopsis viticola

Figure 1c Grape leaf infected with Phomopsis viticola under a light box; the yellow halos are highlighted 

The older, lower leaves are the first to show symptoms. Severely infected leaves may experience premature leaf fall.

On canes and shoots the symptoms are often restricted to the lower internodes. Small dark spots develop on the cane or shoot and with the growth of the shoot these spots expand and elongate to form black lesions 3-6mm in length (Figures 3 and 4).

Figure 3a Small spots develop on the grape stem or cane in spring

Figure 3b Young stem infection of grapevine caused by Phomopsis viticola

Figure 4 Small spots enlarge as the shoot grows to form lesions

These lesions may coalesce to form large scabby areas (Figure 5). The lesions may girdle the shoots as they mature or cause the shoots to become stunted and die. If infection spreads into the rachis, the young bunches may dry out and fall off.

Figure 5a Phomopsis viticola lesions may coalesce to form large scabby areas

Figure 5b Older stem infection of Phomopsis viticola, note the lesions merging into a larger lesion. 

Fruit infection can occur, the berries developing brown spots which enlarge and darken as the disease progresses. The berries may become mummified and fall from the bunch. Fruit infection is rare in Australia.

The disease overwinters as small fruiting bodies on canes and other woody tissue (spurs and prunings), that can often appear bleached with small dark spots. Phomopsis viticola has also been associated with vine decline and grapevine cankers overseas.