Diseases

Question 1

What is meant by plant disease?

Answer 1

Is an unhealthy condition caused by bacteria, fungi or virus (collectively known as pathogens)

Question 2

Describe the damage caused by grey mould (fungus) Botrytis and method of spread.
2 methods of minimising the effects (or preventing).

Answer 2

Grey fuzzy mould on infected parts of plant.
Above ground parts shrivel and die
Mummified flower heads
Spread by wind from one wounded surface to the next.
Humidity control
Cutting out of infected tissue and removal promptly
Thin plants out don’t overcrowd.

Question 3

Describe the damage caused by strawberry powdery mildew and method of spread.
2 methods of minimising the effects (or preventing).

Answer 3

White powdery deposit over Leaf surfaces - upper and lower
Leaves become stunted and shrivelled
Affected fruit stunted and dull in colour or even shrivelled.
Airborne spores
Infect under dry conditions
Mulching and watering.
Prompt removal of infected shoots - don’t shake about.
SB plant invigorator

Question 4

Describe the damage caused by damping off and method of spread.
2 methods of minimising the effects (or preventing).

Answer 4

Emerging seedlings collapse
Some do not emerge
Submerged in mass of white fungal growth
Spread soil borne Asexual spores spread by water and sexual ones infect roots
Pythian and Phytophthora
Minimised by using commercial sterile growing media 
Brand new pots and containers
Sowing thinly
Good ventilation
Mains water
Crop rotation
Cleaning up

Question 5

Outline the life cycle of Damping off fungi

Answer 5

Damp conditions  > PYTHIUM and PHYTOPHTHORA produce asexual spores which are spread in water
Sexual spores (oospores) produced in infected roots and survive several months.

Question 6

Describe the damage caused by honey fungus and method of spread.
2 methods of minimising the effects (or preventing).

Answer 6

Death of plants. First wilting and yellowing .
Sheets of white mycelium below bark
Spread - rhizomorphs spread out underground producing energy for infection and spread of mycelium
Minimise by excavation and destroy and burn all infected material
Digging a trench and placing an impermeable barrier will block rhizomorphs from spreading.

Question 7

Outline the life cycle of honey fungus

Answer 7

Rhizomorphs spread from infected trees conducting nutrients and energy for infection of tough woody shrub and tree roots.
Mycelium then move up r
The stem below the bark.
Sometimes toadstools are produced at base of infected trunk.

Question 8

Describe the damage caused by rose black spot and method of spread.
2 methods of minimising the effects (or preventing).

Answer 8

Rapidly enlarging black patch appears on surface of the Leaf.
Leaves turn yellow around spots and then drop off.
Sometimes leaves stay with lots of small black spots
Small black scabby lesions may appear on young stems
Spread - in water to initiate new infections. Likes warm wet conditions
Minimise by collecting and destroying fallen leaves or burying under thick mulch. Prune out all lesions in spring.
Not really any resistant varieties, shrub roses most resistant.
Fungicide containing Myclobutanil.

Question 9

Name a systemic fungicide ingredient

Answer 9

Myclobutanil

Question 10

Describe the damage caused by potato blight and method of spread.
2 methods of minimising the effects (or preventing).

Answer 10

Wilting, yellowing of foliage then turn black with Wichita bloom on underside of leaves.
Stems may blacken and whole plant die.
Tubers have dark surface spots.
Spread by sporangia blown on wind and land on leaves or stems.
Minimised by buying seed potatoes from reputable source and resistant variety - Sarpo Axona
Rotation of crops
Don’t leave any potatoes in the soil
Burn all diseased material

Question 11

Outline the lifecycle of potato blight fungus

Answer 11

Sporangia are released from infected leaves - blown on wind and then they need water to settle and penetrate into Leaf tissue. Sporangia also infect tubers and infected tubers grow new shoots containing sporangia.
Don’t leave any tubers in The ground over winter - destroy
Crop rotation at least every 4 years
Earthing up
Burn all infected material

Question 12

Describe the damage caused by clubroot and method of spread.

2 methods of minimising the effects (or preventing).

Answer 12

Brassicas stunted and wilted foliage and have purple tint. 
Roots swollen and distorted.
Growth and yield severely reduced. 
Lift and burn diseased plants
Raise soil pH by liming. 
Buy plants from certified grower

Question 13

Outline the lifecycle of clubroot

Answer 13

Resting spores in the ground for up to 20 years.
They germinate and infect root hairs causing distortion
Produces more spores in affected tissue which rots and releases them back into soil.
Brassicas mid summer to late autumn moist warm soil.

Question 14

Describe the damage caused by hollyhock rust and method of spread.
2 methods of minimising the effects (or preventing).

Answer 14

Bright yellow and orange spots on upper Leaf
Reddish brown lumpy spores on underside of Leaf
Starts on lower leaves and works upwards
pustules on stem
stunted growth reduced vigour
Spread by airborne spores
Check and remove infected plants
Monitor bought in plants
Grow as biennial
Avoid dense planting

Question 15

Describe the damage caused by apple and pear canker and method of spread.
2 methods of minimising the effects (or preventing).

Answer 15

Round areas of dead sunken bark usually at a bud or wound.
Cambium layer killed.
Eventual death of branch
Developing fruit sometimes attacked which rot and fall.
Fungus spores spread on wind in spring and enter through damaged parts of plant.
Cut canker out or remove branch and burn.
Improve drainage and raise pH by liming

Question 16

Describe the damage caused by fireblight and method of spread.
2 methods of minimising the effects (or preventing).

Answer 16

Bacterial disease of pears cotoneaster pyracantha
Individual branches wilt and turn brown then whole plant blackens and shrivels as though scorched in a fire.
Spread by insects rain or wind bacteria enter through wounds or stomata
Sterilise pruning equipment with citrus oil
Cut out sections to healthy wood or remove whole infected plants and burn
Cultivar Pyracantha ‘Saphyr Rouge’

Question 17

Describe the damage caused by bacterial canker in Prunus and method of spread.
2 methods of minimising the effects (or preventing).

Answer 17

Bark cracks and dies is increasing concentric rings leaving scars and areas of sunken circles and killed cambium
Gum seeps from canker
Small brown spots appear on leaves which are round and often fall out leaving holes that look like shotgun pellet holes
Bacteria spreads from leaves and enters through stomata of young leaves

Question 18

Outline life cycle of bacterial canker on Prunus

Answer 18

Bacteria exist as surface dwellers and in warm wet weather spring summer enter Leaf through stomata causing infections to develop in young leaves.
As leaves grow and expand infected areas become a shothole
Cankers develop when bacteria gain entry through wounds or Leaf scars at Leaf fall. Dormant until spring when infections spread and kill bark.

Question 19

Describe the damage caused by potato Leaf curl virus and method of spread.
2 methods of minimising the effects (or preventing).

Answer 19

Rolling upwards of leaves caused by an accumulation of starch
Stiff and browny purple
Reduction in potato yield 
rattling sound
Spread by peach potato aphid 
Do not grow potato crop from last years tubers but buy certified seed 
Potatoes that are virus free 
Good hygiene
Burning ng infected crops

Question 20

Damage done by honey fungus

Answer 20

Fails to flower or flowers profusely all of a sudden
Bark cracks and bleeds
Smaller and paler leaves