Agriculture Reference
In-Depth Information
In Australia, a vineyard area can be classed as a phylloxera infested zone, a phyllox-
era risk zone (where phylloxera may exist but the area has not been surveyed), or a
phylloxera exclusion zone (where no phylloxera has been found in surveys). Many
vegetable crops such as tomatoes, potatoes, and carrots, as well as tree crops such
as almonds, are hosts for nematodes that can attack and damage vine roots. Hence
the soil should be tested for the density and types of nematode present. Chapter 5
describes these organisms in more detail, as well as some of the soil-borne patho-
genic fungi and bacteria that attack grapevines (see “Soil Interaction with Fungal
and Bacterial Diseases” in chapter 5). Certain soil and vegetation factors predispose
tobiologicalproblems.Phylloxeradamageisgenerallymoresevereinclayandheavy
clay soils than sandy soils, whereas nematode damage is more severe in sandy soils.
In testing for soil pests and disease, samples of moist soil should be collected by
spade or auger from several locations, bulked, and sealed in polythene bags to be sent
to a qualified laboratory for analysis. A bulk sample should represent no more than
1 to 2 ha. Testing for nematode types and numbers requires moist soil that is kept as
cool as possible until analyzed. If unhealthy vines or other plants are seen onsite, sepa-
rate samples should be taken where these occur and also in apparently healthy areas.
The presence or absence of phylloxera and/or nematodes will determine
whether
Vitis vinifera
cultivars on “own roots” or on rootstocks should be planted.
All
V. vinifera
cultivars are susceptible to phylloxera, as are any rootstocks that
have
V. vinifera
stock in one parental line. Thus although own-rooted cuttings are
cheaper to buy, resistant rootstocks are the only sure way to avoid serious damage
from phylloxera. Chapter 5 discusses the advantages and disadvantages of root-
stocks. Regardless of whether rootstocks are chosen, the cuttings or “rootlings”
(rooted cuttings) should be free from phylloxera, nematodes, and any potential
fungal, bacterial, or viral pathogens (see box 2.5).
Box 2.5 Preplanting Treatment of Rootlings and Cuttings
Hot-water treatment is essential to eliminate nematodes and phylloxera on the
roots of dormant rootlings and to control viruses, bacteria, and fungi that are
potential pathogens in dormant cuttings. The cuttings must be fully dormant
before treatment.
The treatment is as follows:
Rootstocks and
V. vinifera
cuttings Hot water at 50ºC for 30 minutes
Rootlings (bare roots) Hot water at 50
o
C for 5 minutes
Bundles of cuttings and rootlings should be hydrated and brought to ambient
temperature before the hot-water treatment. Immediately after treatment, the
bundles are plunged into clean water at ambient temperature for 20 to 30 minutes.
Those that are to be kept in cold storage before being used may be dipped in a
fungicide such as Chinosol (8-hydroxyquinoline sulfate) to control pathogens.
