PLANT PROTECTION 4

28 The diagnostic road map
CASE STUDIES
The diagnostic road map
These case studies reflect the importance of using a correct diagnostic process.
1. WHIGH SPECIES OF THRIPS?.
A commercial production nursery wanted to
know if the dreaded Western flower thrips
(Frankliniella occidentalis) had reached their
production nursery.
Ornamentals.
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XPERT
Accurate
Brought in samples of flowers and leaves with
thrips. Examined under a dissecting
microscope, but mostly juveniles were found
Illustrations were located and compared but
there was still some doubt.
Samples of flowers and leaves with thrips
were send to an entomologist who confirmed
that it was indeed WFT.
diagnosis of WFT (Frankliniella
occidentalis). Provided client with
information about the pest and who to contact
for advice on its control.
2. WHAT ARE YOUR LIMITATIONS?.
I can identify aphids and other insects. I have
a dissecting microscope but can’t identify
diseases. Why not?
Nematode, viral, bacterial and fungal diseases
can be a little harder to identify. Symptoms
caused by viruses & other diseases are often
non-specific and the micro-organisms causing
the symptoms can often only be observed
using a high powered microscope. Many
require complex testing in a laboratory to
detect and identify.
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You may not be able to access the necessary
books, colleagues and computer sources for
information.
XPERT -
Advice You have to decide how much it is
practical for you to do and what you must
refer to experts.
REVIEW QUESTIONS & ACTIVITIES
1. List the 7 steps in the Diagnostic Road Map.
1.
2.
3.
4.
5.
6.
7.
2. List at least 3 advantages of a systematic
process for diagnosing plant problems.
1.
2.
3.
3. When diagnosing a potential problem a
horticulturist would:
1. Identify the affected plant
2. Be aware of potential problems
3. Check cultural care
4. Do all of the above
4. Give 2 reasons why ‘reducing the
possibilities’ increases the likelihood of a correct
diagnosis.
1.
2.
5. Name 2 reasons why early detection of pests,
diseases and weeds is important.
1.
2.
6. List 2 advantages of using the scientific name
rather than the common name of a pest.
1.
2.
7. For 2 insect or mite pests of your choice supply
the following information:
Common name(s) of ‘pest’ Scientific name
Genus/species
1.
2.
The diagnostic road map
8. For 2 diseases of your choice supply the following
information:
Common name(s) of
disease
1.
2.
Scientific name of cause
Genus/species
9. For 2 weeds of your choice supply the following
information:
Common name(s) Scientific name
Genus/species
1.
2.
10. Distinguish between the following levels of
diagnosis:
Preliminary
Useful
Accurate
Definite positive
Definite negative
Inconclusive
11. How reliable is your diagnosis of pests, diseases
and weeds? Give reasons for you answer.