Plant diseases
By Christopher Rupp
BLACKLEG
• Blackleg is caused by a bacteria with many
strains which also infect stored potatoes,
carrots, bulbs, and damaged tissue causing
Soft rot by dissolving the cell walls.
• prevelant during periods of increased
temperature and humidity.
• There is no treatment so prevention is the
only measure that can be taken.
http://www.dgsgardening.btinternet.co.uk/bla
ckleg.htm
Blackleg continued- prevention
• Use certified 'seed' potatoes which should be
free of the disease.
• If infection occurs remove all affected stems and
tubers - including the original 'seed' tuber which
is most likely the source.
• Space well when planting to improve air flow
which discourages the disease.
• Store at low temperatures, eg. in clamps outside.
• If storing indoors use crates or stout cardboard
boxes which can be regularly inspected.
BLACKSPOT
• fungus spreads by means of asexual spores
(conidia) produced by the growing spots
throughout the summer
• Chemical control must start in early the year
as the leaf buds start to swell and become
vulnerable to spores being splashed up from
debris and stem lesions.
http://www.dgsgardening.btinternet.co.uk/bla
ckspot.htm
Box Blights
• there are two organisms which cause Blight in
the Genus Buxus; both are fungal and they can
occur together
• Volutella has been around for many years. It is
caused by Volutella buxi resulting in browning
of the leaves and dieback of branches leaving
bare patches in hedges and topiary specimens
• It spreads in wet humid conditions
http://www.dgsgardening.btinternet.co.uk/box
blight.htm
continued
• The other Box Blight is more serious, has only
been recognized in the British Isles since the mid
1990s, but is causing great concern
• The fungus Cylindrocladium buxicola produces
symptoms similar to Volutella with defoliated
plants
• The disease requires moist conditions to thrive the asexual spores die in dry conditions. Viable
spores have been found in decomposing leaves
after nearly a year, so any debris should be burnt
if possible - never add to the compost heap.
Brown rot
• Brown rot is caused by the bacterium Ralstonia
solanacearum
• It prefers warm temperate regions, so it infests potato
crops in the UK.
• The symptoms are wilting of the aerial parts of the plant
after it has attacked the vascular bundles in the stem.
• vascular areas are also present in the tubers and it is here
that the disease is most noticeable. A brown ring is found if
the tuber is cut in half; as the disease progresses the ring
rots away completely, and a pale ooze may emerge from
the "eyes" and heel of the tuber.
http://www.dgsgardening.btinternet.co.uk/bro
wnrot.htm
Brown rot continued
• infection is carried in seed potatoes and in
water
• contaminated potato waste should never be
dumped where crops are to be grown or
added to compost heaps. Any affected tubers
left behind after gathering (groundkeepers)
can carry it over to following seasons
Bud blast
• fungal disease which can have a devastating
effect on the blossom of Rhododendrons and
Azaleas
• It is associated with infestations of the
Rhododendron Leafhopper which acts as a vector.
• The infection may enter via the wounds made as
they feed or when the females insert their eggs
into the tissues of the plant.
• the only treatment is removal of affected buds as
soon as possible
http://www.dgsgardening.btinternet.co.uk/bu
dblast.htm
FUNGAL CANKER
• A fungus which infects the branches of fruit
trees causing sunken areas in the bark and
these develop into distorted areas which may
girdle the branch, eventually killing it. Any
shoots which grow are weak, and may break
in the wind.
http://www.dgsgardening.btintern
et.co.uk/cankerapp.htm
CHOCOLATE SPOT
• A fungal disease which attacks Broad Beans
and looks like the leaves have been dusted
with chocolate powder.
• It is favored by acidic growing conditions, lush
growth and damp spring weather. Wintersown crops are more susceptible
http://www.dgsgardening.btinternet.co.uk/cho
colate.htm
CLUB ROOT
• The roots become stubby and swollen and can
develop wet rot.
• This greatly reduces the function of the roots
causing the leaves to become yellow and a
severe stunting of growth
http://www.dgsgardening.btinternet.co.uk/clu
broot.htm
CORAL SPOT
• this fungal disease will migrate to living tissue
after entering via pruning snags and frost
damaged twigs
• Usually found on dead wood
• Small, pinky-orange or coral coloured pustules
will be seen on the bark and these contain the
spores
http://www.dgsgardening.btinternet.co.uk/cor
alspt.htm
Entomosporium Leaf Spot
• disease affects woody members of the
Rosaceae Family but for gardeners it is most
notable with the Photinias
• It attacks mainly fresh growth in the spring
and autumn when the warm moist conditions
it favours are present - temperatures above
14.5°C, 58°F. Small, bright red spots appear on
the upper and lower surfaces of the leaf
http://www.dgsgardening.btinternet.co.uk/ent
omosporium_spot.htm
HONEY FUNGUS
• usually top of the list of diseases which
concern gardeners as it can cause dramatic
damage if it affects a much-loved tree or
shrub which may have been an important
feature.
• The name derives from the honey color of the
mushroom-like fruiting bodies.
http://www.dgsgardening.btinternet.co.uk/ho
ney.htm
POTATO SCAB
• An infection on the skin of the potato
• Raised scab-like patches grow and can split
the surface.
• The flesh of the potato is not usually affected
and after cooking the scab pulls away with the
skin.
http://www.dgsgardening.
btinternet.co.uk/potatosc
ab.htm
POWDERY MILDEW
• A fungus which appears as a dry powdery
bloom on the upper sides of leaves, usually in
hot dry conditions
http://www.dgsgardening.b
tinternet.co.uk/mildewpow
dery.htm
botrytis
• Gray mold can be a problem in greenhouses
when humidity is high and temperatures are
moderate
• first symptom is usually a water-soaked spot. The
tissue later becomes soft and watery. The
affected parts of the plant wilt and collapse. If the
humidity remains high, a grayish-brown coating
or web of mycelium (fungus threads) and spores
develops over the surface of the collapsed tissue.
http://gardening.wsu.edu/library/vege002/veg
e002.htm
Damping off
• variety of fungal problems that lead to sudden
seedling death.
• The pathogens attack the tender stems and roots
of the seedlings. Some seedlings look pinched at
the base of the stem, others flop over, and some
wither away entirely. Once the process is
underway, it’s hard to save even a few of your
plants. Prevention is the best cure.
http://davesgarden.com/guides/articles/view/
277/
phytopthora
• leaves of plants affected by Phytophthora rot
appear drought stressed.
• Trees or plants often wilt and die rapidly with
the first warm weather of the season.
• Leaves may turn dull green, yellow, or in
some cases red or purplish
http://www.ipm.ucdavis.edu/PMG/PESTNOTES
/pn74133.html
Cedar apple rust
• fungal disease
• Symptoms often include swollen growths or
woody galls on branches or shoots
http://plantclinic.cornell.edu/FactSheets/cedar
-applerust/cedar-applerust.htm