PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
CONDITIONS
FAVORING
Conditions favoring development of bacterial diseases may be complex, eg
WEATHER REQUIREMENTS
Different bacterial diseases require different conditions for host plant infection and
disease development, eg bacterial canker infection of stone fruit is favoured by cool,
wet and windy weather. Bacteria thrive in moist conditions and can build up into larger
populations in a short time.
SOIL CONDITIONS
Soil temperatures, moisture and alkalinity may affect the development of soilborne
bacterial diseases.
High soil moisture and temperatures favour bacterial wilt of tomato and capsicum.
Poor drainage may favour some bacterial diseases.
Planting susceptible crops in soil containing infected plant residues.
VENTILATION
Crowded, shady plantings increase disease levels due to poor air circulation around
plants.
PLANT INJURY
Injury to plants by hail, wind-driven rain, irrigation, pruning or pesticide applications
will favour infection. Avoid pruning trees during wet weather.
It is recommended that stone fruit trees be pruned during spring or autumn to allow
pruning cuts to heal rapidly and so lessen the chance of infection by bacterial
canker.
NUTRITION OF HOST
Host nutrition will also affect the development of disease, eg bacteria may more easily
infect and cause damage to succulent shoots.
CONTINUOUS CROPPING
Soilborne bacterial diseases build up in soils if susceptible corps are grown
continually.
ENVIRONMENT
Does it favour the crop or crown gall?
SUSCEPTIBLE
HOST PLANT
Crown gall
BACTERIAL DISEASE
PRESENT
Fig. 153. Bacterial disease triangle.
Bacterial diseases 301