Agriculture Reference
In-Depth Information
Phomopsis cane and leaf blight
Symptoms
Phomopsis cane and leaf blight was formerly known as dead arm, however there
are a number of other diseases of vines that cause similar symptoms. The disease
is caused by the fungus Phomopsis viticola , and it was thought that there were
two types or strains of this fungus in vineyards, type 1 and type 3, which differ
slightly in spore size. Recently type 1 has been renamed as Diaporthe perjuncta .
D.perjuncta is now regarded as non-pathogen to grape vines and is present on vine
material as an endophyte.
All green parts of the vine can be affected by Phomopsis, on leaves the fungus
causes spots while on canes black lesions or scars form. These can become large,
and in fact may girdle the shoot, which leads to death of the shoot. Alternatively
as the shoot matures into a cane, it may snap-off in wind. The fungus over-winters
on canes and spurs, which become bleached (have a white appearance). Eventually
black speckles appear on the surface of the cane. These are fruiting bodies, termed
pycnidia. The pycnidia contain fungal spores which are spread in rain splash and
result in spread of the disease to new shoots in the spring.
Control
For many years sodium arsenite was used to control phomopsis. Dormant canes
used to be treated during the winter period, but these sprays are now no longer
encouraged. One method of control is to ensure that planting material is free of
disease, and vineyard hygiene during pruning is also important in preventing the
spread of this and other wood diseases. Some common fungicides used to control
Phomopsis include Captan, Dithianon and Mancozeb.
Other Vine Diseases
Fruit Rots
There are a range of other bunch rotting organisms that can occasionally attack the
fruit (Table 7.4 ). Many of these are opportunistic pathogens, i.e. infect fruit that has
been damaged or infected first by a primary invader, and some are important post-
harvest rots. Post-harvest rots are of concern in table grape production, where the
fruit might be in storage and transport for extended periods of time. Some examples
of these rots are shown in the table below. All of these rots attack the post-veraison
berry. In most cases little is known about these diseases.
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