Viticulture and Wine Science - Horticulture: Plants for People and Places - page 226

Table 7.4 Summa ry of Bunch rots relevant to grape growing
Bunch Rot Appearance/comments

Alternaria Black. Frequent as a post-harvest rot

Aspergillus Black. Some strains produce a toxin, ochratoxin. Ochratoxin is important

because it is carcinogenic

Colletotrichum Orange sporulation. Occurs mainly in sub-tropical vineyards. Common

name—ripe rot

Greeneria Black sporulation in rings around the circumference of the berry. Widespread

in sub-tropical vineyards. Common name—bitter rot

Penicillium Bluish/green mould. Frequently a secondary invader, occurring in split

berries

Rhizopus Dark black. Frequently a secondary invader, occurring in split berries and

within the bunch

Sour Rot Generally this bunch rot syndrome is caused by a mixture of yeasts, fungal

saprophytes and growth of acetic acid bacteria. Watery berries smell of
vinegar, with a dirty white to brown appearance. Sour rot generally occurs
in ripe fruit (particularly white varieties) that has been damaged

Other Diseases of the Vegetative Structures

We have covered the principal diseases of grapevine foliage; however, there is one
other disease of grapevine leaves that is worth mentioning. Black spot (anthracnose)
is caused by Elsinoe ampelina . Use of the fungicide Ziram largely controls this dis-
ease in most vineyards. As the name suggests this fungus produces black spots on
the leaves and also on fruit (Magarey et al. 1993 ).
There are a number of fungal diseases of the trunk and cane that can lead to a
serious decline in the productivity of the vine. Often the only management option
for these diseases is removal of the affected wood which should be subsequently
burned, and possible re-grafting. Vineyard hygiene during pruning is important in
preventing the spread of these diseases since they are transmitted through wounds.
Some of the more important diseases include Eutypa die back and Botryosphaeria.
Eutypa die back is caused by Eutypa lata , a fungus that produces a toxin eutypine,
implicated in the disease. Symptoms of die back include stunted shoot growth and
dead wood tissue extending back towards the crown of the vine. Symptoms of Bot-
ryosphaeria are similar to those produced by E. lata and it is difficult to distinguish
the two diseases in the field. Botryosphaeria infection of grapevines is commonly
referred to as Bot canker (Savocchia et al. 2007 ). There are a number of fungi that
can also attack grapevine roots. Some of the more common ones are Phytophthora
cinnamomi and Amillaria spp.

Diseases Caused by Bacteria and Viruses

Microscopically bacteria and viruses are much smaller than fungi and their cell
biology is very different. Crown gall is caused by the bacterium Agrobacterium