The Crop Development Division has a unique capacity to
address plant pathology and molecular diagnostics. On a daily basis plant
pathogenic fungi (stem cankers, fruit and root rot) and bacteria are being
isolated and identified from diseased analysis samples. Plant pathogens are
being identified from various deciduous fruit cultivars and hosts.
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Content
Guidelines for
sampling infected plant material, examine the field relating to the problem
Recording of field
information
Collecting and
sending of diseased samples
List of fungal and
bacterial diseases
Guidelines for sampling infected plant
material, examine the field relating to the problem
- Looking for any abnormal condition by traversing the orchard diagonally and
across the backside, and then return to the starting point
Note the distribution of the problem, things such as orchard
characteristics and drainage patterns; only certain rows or low or high areas in
the orchard; soil type and also observe the crop and conditions in neighbouring
orchards
Examine the symptoms: old leaves, leaf abnormalities in
colour, size, shape, and texture, stem cankers, exposure and new growth; insects
or insect damage; vascular discoloration; check leaves for viral symptoms; the
presence of webbing and mites
Carefully dig roots, check for galls, rots, abnormal root
colour, and feeder root condition, and assess growth. Notice odours, insects,
fertilizer placement, and depth of planting in the root zone
- Take soil samples from the root zone
Recording of field information
- Farm details: Date, name, location and plot
Crop: Type (cultivar); growth stage (seedling, mature);
source of stock (seedling, mature plant); cultural practices (irrigated,
sanitation); treatments used (fertilizers, chemicals)
- Symptoms: Description of the part of the plant affected and percentage of
plants infected
- Field distribution: First appearance, spread pattern (scattered or
clustered)
- Environment: Recent weather conditions (dry, hot, wet, cold, windy and
frost); soil type and field situation (slope or other)
- History: New problem or recurring (in area, on farm); previous crop and
usage of pesticide
Collecting and sending of diseased
samples
Select branches that are still alive with symptoms and seal
them in plastic bags to retain moisture. Completely dead branches are of no
value in plant analysis
Collect all infected parts off the tree showing disease
symptoms including roots and soil. Place the root system (with any accompanying
soil) in a plastic bag
- Identifying each sample with a label
List of fungal and bacterial
diseases
Fungal stem cankers:
Botryosphaeria
(Botryodiplodia, Diplodia, Dothiorelle, Lasiodiplodia, Sphaeropsis)
canker
Biscogniauxia (nailhead
canker)
Ceratocystis
canker
Coniothyrium (Leptosphaeria)
dieback
Cylindrocladium (Calonectria)
dieback
Diaporthe
canker
Dibotryon / Apiosporina (black
not)
Eutypa
dieback
Glomerella / Colletotrichum
(anthracnose and dieback)
Hypoxylon
canker
Leucostoma
canker
Microsphaeropsis
dieback
Nectria (Tubercularia, Cylindrocarpon,
Acremonium, “Verticillium”, Fusarium) canker
Neofabraea / Cryptosporiopsis (perennial
canker)
Pezicula / Cryptosporiopsis
(anthracnose, a Gleosporium canker or surface
canker)
Phialophora
dieback
Phoma
dieback
Rhodosticta
canker
Taphrina (plum pockets on stem)
Fungal root rot:
Armillaria root rot
(Armillaria
mellea)
Cylindrocarpon root rot
Phytophthora root and crown
rot
Pythium root and crown rot
Replant disease
(Phytophthora)
Replant disease
(Pythium)
Rosellinia root rot
(Rosellinia necatrix)
Southern Blight
(Sclerotium
rolfsi)
Verticillium wilt
Fungal fruit rot:
Alternaria
rot
Botrytis fruit rot
Cladosporium
scab
Monilinia blossom blight
Bacterial diseases:
Blister bark
(Pseudomonas syringae pv. syringae)
Blossom Blast
((Pseudomonas syringae pv. syringae)
Bacterial
canker (Pseudomonas syringae pv.
morsprunorum)
Bacterial spot (Xanthomonas
campestris pv. pruni)
Crown gall (Agrobacterium
tumefaciens)*
* Only visual identification
