PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
CONTROL
METHODS
(contd)
For many plants,
resistant to root knot
nematodes are yet to
be found or only partial
resistance is available, eg
no turfgrass is known
to be resistant to the
feeding of all nematodes
Exotic nematodes
have probably been in
Australia for many
years before being
detected and
identified, eg potato
cyst nematode
To minimize grapevine
losses due to
nematodes, current
management practices
include hot water
treatment of grapevine
planting material,
nematode-resistant
rootstocks and
nematicides
RESISTANT, TOLERANT VARIETIES AND ROOTSTOCKS.
When varieties with desired horticultural qualities of resistance or tolerance and suited to
local conditions, are available, their cultivation is the most effective and convenient way
of reducing losses from nematodes, especially when used with effective rotation crops.
Some newer varieties are not only resistant to nematodes, but may be resistant
to other diseases or pests and be available as disease-tested planting material. The
search is on now for varieties of bananas and other crops with resistance to several
nematode species and soil diseases.
Cereal cyst nematodes (Heterodera spp.) and root lesion nematodes
(Pratylenchus spp.) cause significant losses around the world. Screening programs
can assess resistance to each of these species.
Sugarcane is subject to more serious nematode infestations than any other crop
in Australia, at least 8 genera are reasonably common in most sugar growing
countries so crop rotation, minimum tillage residue retention, etc.
Crops can be genetically engineered to be either resistant or at least have
some tolerance to a particular species of nematode. Transgenic grapevines and root
stocks with resistance to several nematode species could be developed.
Synthetic plant resistance is a new approach to control of plant parasitic
nematodes. Plant activators can stimulate the plant’s resistance mechanisms.
Nematode-resistant rootstocks.
– Some tomato varieties show some resistance to certain nematodes (and other soil
diseases). Their inclusion in a crop rotation can be as useful as growing a non-host.
– Grapevine ‘Harmony’ has some resistance to the dagger nematode and the grape
phylloxera (a gall aphid).
– Peaches, nectarine, plums and apricots are generally propagated on peach
seedling rootstocks. Seed is usually obtained from cannery seed. Only the seed from
a true-to-type Nemaguard parent tree can be guaranteed to have resistance to root
knot nematode, not seed from a Nemaguard seedling.
PLANT QUARANTINE.
Australian Quarantine and Inspection Service (AQIS). Many plant
parasitic nematodes have not as yet reached Australia, eg soya bean nematode, or if
they have, their distribution is restricted, eg potato cyst nematode.
For target lists of insects, plant and animal pests and diseases and weeds, visit:
www.daff.gov.au/aqis/quarantine/naqs/target-lists
PaDIL (Pests and Diseases Image Library) www.padil.gov.au/
Interstate and Regional Plant Quarantine. Health certificates are required
for rye seed and hay produced in SA and moving into NSW and Victoria to limit risk
of spreading annual rye grass toxicity (ARGT) (page 253). Potato cyst nematode in
WA has restricted the movement of potatoes to other States/Territories.
‘Local’ quarantine. Nematodes can be introduced to nurseries, orchards via:
– Infested plant material (plants, bulbs, seedlings, tubers, nursery stock).
Suspect plants should be kept isolated until non-infection is confirmed.
– Soil (in containers, pots, soil deliveries). The roots of all purchases should be
inspected and plants kept separate until proven healthy.
DISEASE-TESTED PLANTING MATERIAL.
Only use nematode-tested planting material and only take propagation material from
healthy plants and only plant in nematode-free soil (treatment may be required).
Infested vegetative planting material (runners, bulbs, rooted nursery stock,
tubers, seedlings) can be effectively treated. Treatments include:
– Hot water treatments (bulbs, strawberry runners, rose/grapevine nursery stock).
– Chemical dips (banana corms).
Inspect/test all new purchases (cuttings, seedlings, tubers etc) if appropriate,
for nematode infestation, as their introduction by this means often results in rapid
spread. Remember they may have been shipped before symptoms were visible.
Grow one's own seedlings and other propagating material as far as possible,
and plant in soil or media free from nematodes or in soil which has been
pasteurized, fumigated or treated with a nematicide.
PHYSICAL AND MECHANICAL METHODS.
Heat is the only physical method used to control nematodes. Usually limited to high
value crops and/or small areas.
Hot water treatment (HWT) is used to treat daffodil bulbs, strawberry runners
and rose nursery stock; also grape cuttings to rid them of phylloxera, nematodes,
root rotting fungi and bacteria. Seek expert advice on treatment.
Soil pasteurization. Heating soil to 60 o C for half an hour will rid soil of parasitic
nematodes and fungal diseases. Only suitable for small quantities of soil such as in
glasshouses and cutting beds.
Soil solarization. Clear plastic stretched over moistened soil, traps solar energy
to heat the soil and suppress soil fungi and nematodes. The soil to the depth of
15cm must be consistently heated for at least 3-4 weeks in the hottest conditions
(may reach 52 o C in the top 5 cm) and for several months in the cooler months.
264 Nematode diseases