PLANT PROTECTION 4

ACCESS TO INFORMATION
Correct identification of affected plants means that information about its culture, its pests and diseases can be
accessed.
LEGISLATION
A NORMAL
PLANT
REDUCING
THE
POSSIBILITIES
LIST OF PESTS
& DISEASES
Roses
Virus diseases
Rose mosaic
Bacterial diseases
Crown gall
Fungal diseases
Anthracnose
Black spot
Powdery mildew
Downy mildew
Petal blight
Rust
Insects, mites
Aphids
Plague thrips
Rose scale
Twospotted mite
Non-parasitic
problems
Iron deficiency
Herbicide injury
The status of a crop may differ depending on the situation, eg commercial crops,
public parks or home gardens.
For quarantine and trade purposes. Knowledge of the relationship between
Australian plants and those belonging to other geographic regions is vital to
preventing exotic introductions. Weed risk assessment is carried out for all
imported plants.
Registration and use of pesticides and bio-pesticides. Most insecticides and
fungicides are only registered for use on certain plants. Some are not registered for
use on edible crops, some can only be applied at certain stages of crop growth. So
you may need to identify different stages of plant growth, eg seedlings, pre- and postflowering,
fruiting, post-harvest, dormant rootstock, mature plants.
CROP DISEASE STATE RATE HOW TO APPLY
Almonds Leaf curl
Shothole
38 Diagnosis - Step 2. Identify affected plant
Spray at budswell before
and within one week of
bud opening, etc
Apples Black spot (scab) Spray at green tip stage,
etc
Apricots and Shothole
Spray at early budswell
cherries Freckle
prior to earliest stage of
bud movement, etc
Sale of plants. Assist customers in purchasing correctly named plants suitable for
their garden and the surrounding environment. The customer is entitled to expect
that the botanical name is included somewhere on the label.
To diagnose abnormalities you need to know what a normal healthy plant of the same
variety and age looks like in your region. Most horticultural references are organized
by host, so once the name of the plant is known, you can look up references or ask
someone about its culture. Is it naturally variegated? Is it supposed to be a dwarf
variety? Are stems naturally hollow?
Hundreds of pests and diseases may occur in your area - a formidable number to
choose from. However, most plants are only susceptible to a few economic pests. By
identifying the affected plant you can:
Reduce potential problems to a manageable number. You have immediately
reduced the number of possible problems from hundreds to those that typically occur
on that species or variety. For example, if the host is a rose, you can narrow down
the possible problems to the 20 or so pests and diseases that affect roses.
Learn how to distinguish one problem from another on a particular plant
(pages 52 and 53).
You can access lists of the common pests and diseases of your crop. This list offers
suggestions of what your plant problem might be, but any diagnosis must ultimately be
proved by appropriate diagnostic techniques.
Get to ‘know’ the pests, diseases and weeds likely to affect your crop in your region.
A realistic goal for a grower is to select 6-10 important recurring problems in their
crop and obtain information about them. Prioritize (list 1-10) them according to their
economic or aesthetic significance, quarantine importance, etc.
This list may enable you to eliminate pests and diseases that do not need to be
considered. This can be just as important as knowing what it is, eg it is not rust on
walnut because walnut is not a host for rust.
Knowing which species or cultivars are susceptible to the common problems in
your region will assist with plant selection.
Although lists of common problems are helpful, remember that both country and
urban environments are constantly changing and exotic introductions are a regular
occurrence. Some pests may occur out of their normal environment in protected
sites, eg in greenhouses, courtyards. Under some circumstances, some pests and
diseases may attack unusual hosts, eg black scale has been found on potatoes, brown
rot may attack quince. Be familiar with new crops and their associated pests.
Contact quarantine for recent pest introductions in your region.
If a host is not listed, selecting a closely related species may be useful but be cautious.