Agriculture Reference
In-Depth Information
Grape phylloxera and eggs on a root of
Vitis vinifera.
© The State of Victoria, Department
of Natural Resources and Environment, 2001. Reproduced by permission of the
Department of Natural Resources and Environment and therefore is not an official copy.
Photograph by Greg Buchanan. See color insert.
Figure 7.11
to waterlogging, than in sandy soils. In Australia, phylloxera is not expected to in-
vade soils with
70% sand. For example, in the Nagambie Lakes Subregion in
central Victoria, a small plot of Shiraz vines survived phylloxera at the end of the
nineteenth century because they were growing on a sandy ridge in an alluvial plain
of clay loams (section 9.7.3).
Because phylloxera starts from a point source and spreads outward in a circle,
the organisms are most easily found on mildly affected vines at the edge of an in-
festation, for example, on fibrous roots within 0.5 m of the base of the vine dur-
ing summer (phylloxera are dormant in winter and shelter under bark on the roots).
As the population increases, new areas of infestation occur at other sites around
the original. The spread is rapid in the first 3 to 4 years, and after 8 years or so
the vines are so affected as to be unproductive and subsequently die. The organ-
ism spreads on planting material and machinery moved from an infested vineyard
to a clean one. Dispersal of the winged form (see fig. 7.10) is uncertain, but flood
or furrow irrigation water can move the pests, as can soil erosion by water.
Control of Phylloxera
. No insecticide is effective on phylloxera in the vine-
yard. The prime method of long-term control is to use cultivars that are grafted
onto resistant rootstocks. In planting material (cuttings and rooted cuttings or
“rootlings”), phylloxera can be controlled by using a hot water treatment, which
is also used for the control of nematodes, crown gall, and phytoplasma diseases
(appendix 13).
The choice of rootstock is complicated by the need to consider not only re-
sistance to phylloxera, but also resistance to nematodes (section 7.3.3.2), tolerance
of drought and salinity (section 7.2.2.3), sensitivity to lime-induced chlorosis (sec-
tion 5.5.2), and compatability between scion and stock, particularly as it affects
vine vigor and grape quality.
