Agriculture Reference
In-Depth Information
Biological Control in Vineyards
There are many soil-borne pests and disease organisms that affect grapevines
directly or indirectly. Various chemicals are used to combat these pests and dis-
eases, so it is important to know the fate of these chemicals and their residues in
soil and the wider environment. Consumers are concerned about (a) the impacts
of grape growing and winemaking on soil and water quality and human health,
and (b) the “C footprint” of winegrowing. Consequently, winegrowers are inter-
ested in biological methods and less energy-intensive methods of controlling vine-
yard pests and disease, as well as the beneficial use of waste products, as discussed
in “Winery Waste and the Soil” later in this chapter. Rootstocks offer one of the
most effective means of specific pest control in vineyards.
The Function of Rootstocks
Varieties of
Vitis vinifera
(the scion) can be grafted onto rootstocks that are bet-
ter adapted to particular soil and site conditions. Initially, the prime purpose of
such grafting was to enable vinifera varieties to resist the attack of phylloxera.
This pest, endemic in North America, was accidentally introduced into France
in 1862, nearly devastating the wine industry and subsequently having a seri-
ous effect on wine production in many other countries. Native American
Vitis
species such as
V. rupestris
and
V. riparia
that are resistant to phylloxera were
investigated as rootstocks for grafting, mainly at Montpellier in France, where a
statue commemorates the rescue of the ailing French vines by vigorous American
rootstocks (figure 5.11). Other native American species such as
V. champini
and
V. berlandieri
were subsequently introduced into the grafting program, and many
crosses have been made using these foundation species.
The four species commonly used for rootstocks have evolved in distinct
regions of North America and hence vary in many of their characteristics other
than their resistance to phylloxera. Although phylloxera remains a potentially seri-
ous pest in many grape-growing regions around the world, other pests such as
parasitic root nematodes are also widely recognized as a potentially serious prob-
lem. Furthermore, grafting of desirable varieties of
V. vinifera
onto a rootstock can
offer other advantages such as salt tolerance, drought tolerance, tolerance of free
lime (CaCO
3
) in the soil, combating excess vigor on high-potential sites or low
vigor on low-potential sites, and control of vine balance (affecting yield and fruit
quality). Thus in addition to the initial four native American rootstock varieties,
other varieties have been investigated in breeding and selection programs in an
effort to develop commercial rootstocks with a range of desired attributes. For
example, in Australia, while phylloxera and nematode resistance are important
aims in current breeding programs, rootstock crosses are also being developed to
