Agriculture Reference
In-Depth Information
Control of Pests and Disease
In addition to beneficial organisms, vineyard soils harbor organisms that can dam-
age or kill the vines. Pest and disease organisms fall into four groups: insects, most
seriously phylloxera (
Daktylasphaera vitifoliae
), several types of nematode, verte-
brate pests, and pathogenic fungi and bacteria.
7.3.3
Phylloxera
Phylloxera is an aphid that lives on vine roots and occasionally in galls on vine
leaves. The first aboveground symptoms of attack are premature yellowing of the
leaves near harvest time. Progressively, the vines decline in vigor, suffer stunted
growth, and finally die. The insect is endemic in the eastern United States, where
the native species of
Vitis
are resistant. However, European species of
Vitis
are not
resistant. When the pest was introduced to Europe around 1860, and subsequently
to other parts of the world in the latter part of the nineteenth century, the wine
industry based on
V. vinifera
varieties was devasted. A breeding program was es-
tablished in France to develop hybrids of the favored European varieties as scions,
grafted onto resistant American rootstocks. This ongoing program has been so
successful that grafted rootstocks should be used as planting material in any area
where phylloxera occurs or has occurred in the past.
Epidemiology
. The life cycle of phylloxera is illustrated in figure 7.10. Infected
roots swell and become clublike (fig. 7.11), which stops rootlet growth and im-
pairs water and nutrient uptake. The severity of the attack depends on the vari-
ety (whether a resistant rootstock or “own roots”), vine age and vigor, and soil
type. Phylloxera is a greater problem in heavy clay soils, especially if they are prone
7.3.3.1
The life cycle of phylloxera in California (from Flaherty et al. 1992). Reproduced with
permission of Division of Agriculture and Natural Resources, University of California.
Figure 7.10
Ground
Winged form
(Rare)
Migration to root
Nymph
Adult
Cycle on
roots
Eggs
Infested
Eggs
root
Healthy root
Nymph
Nymph
with
wing pads
Adult
