Agriculture Reference
In-Depth Information
Soil Interaction with Fungal and Bacterial Diseases
Some grapevine disease organisms reside in soil. For others, soil management influ-
ences the severity of the disease or the actions taken for disease control affect the
soil. Maintaining a species-diverse cover crop and/or mulching is helpful, if not in
eliminating disease at least in controlling the incidence of disease to a degree that
spraying programs can be much reduced or even made unnecessary. The benefit
seems to derive from a more active and biodiverse soil microbial biomass, which is
stimulated by an increase in readily available SOM and suppresses soil pathogens.
Although not soil-borne, the fungus (
Botrytis cinerea
) that causes bunch rot or
gray mold survives on mummified fruits, so vineyard hygiene is important. Research
in the Marlborough region, New Zealand, has shown that an under vine mulch of
shredded office paper can reduce the incidence of gray mold to the extent that spray-
ing is not needed. Mulching seems to work by improving the decomposition of vine
debris, increasing competition between soil microbes and the fungus, and strength-
ening the skins so that the grapes are more resistant to fungal attack. Another exam-
ple comes from the Griffith region, New South Wales, Australia, where the fungal
root pathogen
Cylindrocarpon
spp., the cause of “black foot” in grapevines, was
inhibited by green manure and compost treatments (Weckert et al., 2009).
Examples where disease control affects soil properties include the spraying
of vines with wettable sulfur (S) to control powdery mildew (
Uncinula necator
).
Regular use of S sprays over many years can decrease topsoil pH (see “Sulfur,”
chapter 3). Another example is that of downy mildew (
Plasmopara viticola
), which
overwinters on leaves in the soil. Spores that are splashed onto the foliage by rain
(>10 mm), when temperatures are more than 10ºC for at least 24 hours, will
germinate and infect the leaves. Downy mildew has traditionally been controlled
by copper (Cu) sprays (Bordeaux mixture and other Cu-based fungicides), which
have led to potentially toxic Cu concentrations in many topsoils in the Bordeaux
region, France. Similarly, a survey of vineyard soils in Victoria, Australia, found
that just over half the soils examined had topsoil Cu concentrations that exceeded
Australian and New Zealand guidelines (Pietrzak, 2009).
Winery Waste and the Soil
Types of Waste and Potential Beneficial Uses
In regions as far afield as the Central Valley of California, Mendoza Province,
Argentina, La Mancha, Spain, and the Murray-Darling region in Australia, wine-
growers are experiencing increased competition for water from other industries
and for the environment and rising water prices. Furthermore, stricter controls
have been placed on the discharge of untreated winery wastewater into surface
