PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Management (IDM)
Are you a commercial grower or home gardener?
1. Obtain/prepare a plan in advance for your crop.
2. Crop, region. Recognize variations. Rusts may be
more severe in some areas than others.
3. Identification of disease must be confirmed. If
necessary consult a diagnostic service (page xiv).
4. Monitor and detect disease on the most
susceptible varieties, seedlings, earliest sown crops
and sentinel crops along certain walking patterns as
they are most likely to develop early rust. Inspect leaf
undersurfaces for pinpoint spots but experience is
needed to detect this early stage of infection, also look
for spores. Record findings. Early warning systems
are available for some rusts, eg Prune Rust Infection
Predictors, Stripe Rust Alert Services.
5. Threshold. Quarantine regulations may require a nil
threshold in some crops. How much damage can you
accept? What is your threshold, eg economic, aesthetic,
environmental?
6. Action/control. Take appropriate action when any
threshold is reached. This may involve removing/
destroying affected plant parts, spraying it may be
following some prescribed control measures.
7. Evaluation. Review IDM program to see how well
it worked. Recommend improvements if required, eg
planting more resistant cultivars, rust-tested seed.
Control methods
Cultural methods.
Avoid high rust hazard zones.
Avoid planting seed or cutting beds too thickly.
Keep foliage as dry as possible. Avoid overhead
irrigation, or water early in the day to allow crop to
dry. Sub-irrigation helps prevent rust outbreaks.
Provide adequate ventilation, reduce humidity,
maintain even temperature to reduce infection.
Where rust causes severe losses and no resistant
varieties are available it may be possible to plant
early in the season so that plants can make good
growth before development of an epidemic.
Sanitation.
Remove and destroy severely infected plants, fallen
leaves, crop regrowth, volunteer seedlings, crop
debris and prunings as soon as practical to reduce
the amount of inoculum available for next season.
Remove infected leaves or whole plants in cutting
or seedbeds, as soon as they are observed.
Susceptible tree species generally should not be
removed, rust may be minimal during dry seasons and
trees may survive for years despite rust.
With rust diseases which produce galls, infected
branches can be pruned out and burnt.
Susceptible weeds should be controlled.
Do not plant susceptible crops near older diseased
crops. Plough in crops immediately after harvest.
Biological control.
Some fungi are parasitic on rusts but provide no
economic control, eg Verticillium lecanii on coffee
rust, Cladosporium sp. on poplar rust.
Resistant varieties.
Use of resistant varieties is the most common,
effective method of rust control www.grdc.com.au/
The National Wheat Rust Control Program
screens wheat lines for resistance. As rust fungi
regularly develop new virulent strains, ongoing
screening and selection is necessary to maintain
resistant varieties for wheat growers. Rust genes
from plants other than wheat could potentially be
transferred to wheat. ‘Designer’ genes providing
more durable resistance could be developed.
Combining two or more resistance genes in
sunflowers is expected to produce robust protection.
Even cultivars with partial resistance to rust are
useful because they reduce the amount of fungicide
used, eg antirrhinum and carnation rust.
Plant quarantine.
New rusts enter Australia all the time; recent arrivals
include grape leaf rust (Phakopsora euvitis). A
National Grapevine Eradication Program was put in
place and the disease has since been eradicated.
Although eradication of other recent entries may not
really be possible, eg myrtle rust (Uredo rangelii),
chrysanthemum white rust (Puccinia horiana), daylily
rust (P. hemerocallidis) and its alternate hosts, eg
Hosta, Patrinia, they are subject to regulations and
local protocols. Check.
An Asian-Pacific Strategy manages the threat of
Eucalytpus Rust (Puccinia psidii).
Disease-tested planting material.
Avoid propagating vegetatively from infected plants.
Do not save seed from infected plants, if such seed
is to be used it must be treated.
Fungicides.
Rusts are suppressed by fungicides, not eradicated.
Some rusts occur in crops such as wheat which
cannot be economically sprayed or on plants such
as poplars which are too tall to spray.
Foliage sprays and dusts are only practical for
small areas, eg orchards, nurseries, gardens.
Begin treatment at an early stage of infection as
advanced rust outbreaks are difficult to control.
And thoroughly spray all plant surfaces.
Risk of resistance. The rusts of wheat and
barley are accepted as having a medium risk of
developing
resistance to fungicides. Follow
Resistance management strategies available for
some crops and rusts on the CropLife Australia
website www.croplifeaustralia.org.au/
Follow label Resistance Management Strategies.
Overseas soil drenches and tree injection are used to
control rust diseases with systemic fungicides.
Table 64. Rusts – Some fungicides.
What to use?
NON-SYSTEMIC FUNGICIDES (protectants)
Group M1, eg copper hydroxide; copper oxychloride
Group M2, eg Dusting Sulphur; Kumulus , Lansul ,
Sulfine (dispersible sulphur); Lime Sulphur
(polysulphides)
Groul M3, eg mancozeb
SYSTEMIC FUNGICIDES (eradicants)
Group 3, eg Baycor (bitertanol); Saprol (triforine);
Tilt (propiconazole)
Impact (flutriafol) may be applied as a foliar
sprays or as in furrow as a fertilizer treatment
Group 7, eg Plantvax (oxycarboxin)
SEED DRESSINGS
Wide range of seed dressing are available
See also page 374
BIO-FUNGICIDES (non-systemic)
Some products are being researched.
When and how to apply?
Sulphur has long been a specific remedy for rust.
Sulphur may scorch some species at > 30 o C, eg begonia, softfoliaged
plants. Flower petals may be very susceptible
Sulphur is often included in all-purpose garden sprays or
dusts, eg rose or vegetable sprays and dusts.
Mancozeb is probably the most widely used fungicide for
rust diseases.
Apply systemic fungicides at the first sign of rust.
Frequency of further applications depends on weather.
Generally if you can see the rust pustules then systemic
fungicides are usually required.
If disease is well established do not try to spray, remove/
destroy severely affected plants and self-sown seedlings.
Most rust diseases are seedborne.
Sulphur is used occasionally as a dust or dip to kill the rust
spores which adhere to the outside of seed.
354 Fungal diseases - Examples of fungal diseases