Plant diseases can infect and damage important agricultural crops. Some key plant pathogens discussed in the document include damping off fungi like Pythium and Rhizoctonia; Botrytis cinerea, which causes gray mold; Elsinoe veneta that causes cane spot on raspberry plants; and Didymella applanata that causes spur blight in raspberries. The document provides information on disease symptoms, overwintering habits of pathogens, and both chemical and non-chemical control methods to manage common plant diseases.
3. Damping Off
Non-chemical control
Raise seedlings in commercial growing compost.
Sterilisation to destroy pathogens.
Ideally, use new pots and trays.
Sow seedlings thinly to avoid crowding.
Use mains water if possible when irrigating.
Do not overwater.
Keep seedlings well ventilated to reduce humidity.
Soil-borne fungi including
Pythium, Rhizoctonia &
Chemical control
Fusarium,
The copper fungicide Fruit and Vegetable Disease
which infect seedlings and cause
Control is very effective if applied as a
them to ‘damp off’ or collapse
preventative drench to seed trays.
and decay.
5. Botrytis cinerea
Economically Important
To minimize infection in strawberry fields,
good ventilation around the berries is important
to prevent moisture
being trapped among leaves and berries.
May cause "winegrower's lung”
7. Cane Spot [Elsinoe veneta]
Over
winters
on
the
canes!
First appear on the lower parts of the canes, &
gradually work their way upwards.
The marks tend to be in the shape of a 'squashed' circle (elliptical) and are
rarely larger than 1cm (1/4 in) long.
Regular clearing of debris at the base of the plant will prevent it's spread.
9. Spur Blight [Didymella applanata]
Purple patches.
Rarely kills raspberries - reduce yield & weakens canes/killing buds.
Appears from late summer and persists on infected canes until the following year.
Particularly common during wet seasons.
Fruiting bodies of the fungus may be visible as tiny black spots on the affected areas.
Many of the buds on canes infected the previous year fail to grow.
Copper oxychloride - spray canes in spring or evening.
Resistant cultivars -‘Glen Lyon’, ‘Glen Moy’, ‘Glen Rosa’, ‘Julia’, ‘Leo’ & ‘Malling Admiral’
11. Rust [Fungi of the order Pucciniales]
Disease is systemic
Reducing blossoming and fruit set
Does not kill - no value
Source of inoculums - spreading
the disease
Good hygiene & careful watering
Destroy
Fugicides such as Mancozeb or Triforine
Organic preventative - Sulphur powder
Most harmful pathogens to agriculture & horticulture
13. Tulip Fire [Botrytis tulipae]
Spores attack emerging tulip leaves
Brown spots leading to rotting –
foliage & flowers
In heavy rain the flower stem collapses
& the whole plant can end up covered
in fungus
Destroy
Plant in November,
rather than early autumn –
soils are colder,
so the fungus is less likely to spread
15. Fire Blight [erwinia amylovora]
Rosebushes,
Apple & Pear Trees
Attacks blossoms or flowers & moving up to the twigs and branches
Flowers turn brown & wilt - twigs shrivel & blacken
Advanced cases - cankers, discoloured oozing patches
Amber or reddish ooze contains masses of bacteria
Heavy persistent infections can be fatal
17. Crown Rot
Hemerocallis
[Daylily]
&
Hosta
Leaves start to discolour, wither, and die off –
whole plant may droop
Stems my darken in colour, have a slick texture or mushy feeling
Avoid over watering or allowing plants to dry out totally
19. Parsnip Canker [Itersonilia pastinacae]
Orange, brown or purple-coloured
rot usually starts at the top of the root
Drought, over-rich soil or damage to the
crown
e.g. Carrot-fly injury and damage from
hoeing
Low or acid pH also makes the disease more
likely and more severe
Sow resistant cultivars such as
‘Avonresister’ & ‘Archer’
Avoid sowing seeds too early in the year
21. Halo Blight [Pseudomonas syringae pv. Phaseolicola]
Water droplets - rain or watering carry the spores
Plant disease-free seed, rotate crops
Destroy
Soap-Shield® Fungicidal Soap [US] or Copper Fungicides at 7-10 day intervals
23. Tomato Mosaic Virus
[ToMV]
Light & dark green mottling of the leaf tissue and stunting of the plant
Upward leaf rolling & stem streaking depending on which strain of ToMV
Resistant varieties is the best way to reduce losses from this disease
Avoid planting in soil from previous crops that were infected with ToMV
Snapping off suckers without touching the plant instead of knife pruning can
help reduce disease incidence
25. Tomato Spotted Wilt Virus
[TSWV]
Serious diseases of many economically
Destroy important plants representing
35 plant families, dicots & monocots
TSWV transmitted by certain thrips
Symptoms expressed on leaves, petioles, stems & fruit
Young leaves may show small, dark-brown spots and eventually die
Dark brown streaks also appear on stems and leaf petioles
Growing tips are usually severely affected with complete cell death &
greatly stunted growth
27. Potato Leaf Roll Virus
[PLRV]
Coarse, brittle & rolled
along midrib
Significant yield &
quality losses