plant disease is defined as any condition caused by
organisms such as fungi, bacteria and viruses. In almost
all cases the health and growth of the plant is affected
and in some cases the plant dies.
with cultivated pest resistant plants there are disease
resistant plants that are widely available. For example
are resistant to powdery mildew, rust and black spot.
established infections are extremely difficult to
contend with so catching them early is a must. Removal
of sections or the whole plant is often necessary to
prevent the disease from spreading. Unlike pest infected
plants it is not wise to compost your infected plants
but instead burn or discard them. This includes fallen
leaves that are infected. Always clean your pruning
tools after use.
is also worth getting rid of the top soil around the
plant especially if you wish to replant with the same
can be used to minimise disease. Contact fungicides may
kill fungal spores and prevent spreading but are almost
useless on established infections. Systemic chemicals
work by being absorbed into the plant. Fungi is then
killed from the inside out. Overuse of fungicides can
promote immunity in some diseases.
spraying pesticides or fungicides on plants in direct
sun, or when they are dry as this will prevent damage
to the plant.
the remains of old, rotting or infested plants properly. Dig up &
destroy those with virus symptoms so that the problem does not spread to other
plants. Keep on top of weed control, particularly near the vegetable plot
because weeds often act as a host for pests.
growing too close together compete for light, water & nutrients and
cannot grow to their potential. Overcrowding also prevents good air
circulation, allowing fungal diseases to take hold.
not to damage plants, lesions & cuts on plant tissue can be an entry
point for disease. Use sharp tools for pruning and make clean cuts just
above a bud to prevent die back. Check the stakes & ties on trees
& shrubs, they must be secure so that they don't rub & damage the
In the warm
conditions inside a greenhouse, young plants are particularly vulnerable
to attack. Raise seeds, cuttings & young plants in clean pots. Use
fresh compost and tap water rather than rain water. If you have a water
butt for watering your plants with rainwater, empty & clean it out
once a year.
- Buy varieties of
plants that are resistant to pests & diseases. Look for the first
Summer - Diseases can
often take hold when plants are overcrowded, so space
accordingly and ensure good air circulation.
Winter - Clear
fallen leaves & burn any that show diseases. In the greenhouse
maintain good ventilation to avoid grey mould. Clean greenhouse &
equipment with garden disinfectant.
- A common fungal disease that attacks plants leaving pale and
dark spots on the leaves. Prune away all affected leaves and burn
them. Spray roses in winter with an anti black spot remedy or
tar-oil wash. In early spring spray with a rose fungicide or with
sulphur and mulch the ground at the base of the plant with compost.
- A grey white powder on leaves and buds. Severe attacks can cause
leaves to fall. Mildew is brought on by dryness or lack of
nutrients. Spray with a rose fungicide or with sulphur at the first
signs of attack. Water and feed your affected plant more often and
mulch around the base.
A problem in mild and wet summers. Orange postules develop of the
underside of the leaves and can cause premature defoliation. Spray
with a rose fungicide that works on rust, or use a fungicide
Mould / Botrytis - Fuzzy
grey fungal growth on foliage. This causes
discolouration and rapid deterioration. Infection may
spread to plant. Plants affected are perennials,
annuals, trees, shrubs, fruits, vegetables and indoor
plants. Venerable plants are those with soft leaves.
kernoviae are fungus-like pathogens which can
kill some types of shrubs and trees, such as the
European beech, and pose a threat to garden plants,
woodlands and native heathland.