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.


Plant Pathology

Diagnostician: Smit, L. (B.Sc.)


Microbiologist: Petersen, Y. (Ph.D.)
Microbiologist:: Langenhoven, W. (M.Sc.)


  • 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

  1. Looking for any abnormal condition by traversing the orchard diagonally and across the backside, and then return to the starting point
  2. 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
  3. 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
  4. 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
  5. Take soil samples from the root zone

Recording of field information

  1. Farm details: Date, name, location and plot
  2. Crop: Type (cultivar); growth stage (seedling, mature); source of stock (seedling, mature plant); cultural practices (irrigated, sanitation); treatments used (fertilizers, chemicals)
  3. Symptoms: Description of the part of the plant affected and percentage of plants infected
  4. Field distribution: First appearance, spread pattern (scattered or clustered)
  5. Environment: Recent weather conditions (dry, hot, wet, cold, windy and frost); soil type and field situation (slope or other)
  6. History: New problem or recurring (in area, on farm); previous crop and usage of pesticide


 Collecting and sending of diseased samples

  1. 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
  2. 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
  3. Identifying each sample with a label


List of fungal and bacterial diseases

Fungal stem cankers:
(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