Organic Control Options for Vegetable Diseases

1. Common diseases of vegetable crops in
New Brunswick, 2014-16
Michael Tesfaendrias, Ph.D., P. Ag.
NBDAAF
IPM Specialist (Plant Pathologist)
(506) 453 3478
Michael.tesfaendrias@gnb.ca

2. Plant Disease
• Infectious (biotic)
– Fungi (early blight)
– Bacteria (soft rot)
– Nematode (stem and
bulb nematode)
– Protozoa (club root)
– Phytoplasma (aster
yellows)
– Virus (iris yellow spot)
• Non-infectious (abiotic)
– Too low or too high Temp.
– Drought or excessive
moisture
– Lack or excess light
– Air pollution
– Nutrient deficiency,
mineral toxicity, soil pH
– Pesticide toxicity
– Improper cultural practices

3. • Infectious (biotic) • Noninfectious (abiotic)

4. Disease Development
Disease can be prevented upon elimination/manipulation of any one of the
disease triangle components
Susceptible
Host
Pathogen
Environment
(favourable)
Disease

5. Role of insects in plant diseases
• Insects can transmit disease (virus, phytoplasma)
• Wounds created by insect feeding: ideal entry point for
pathogens
Aster yellows
Onion thrips
Tarnished plant bug
Fungal spores
Aster
leafhopper

6. Flea beetle
Cabbage maggot

7. Vegetable disease management
• Integrated Pest Management (IPM): an approach to
managing pests that uses all available strategies to
reduce pest populations below an economic injury level.
– Monitoring: weather conditions, plant health, disease
symptoms
– Cultural methods: site selection, crop rotation,
resistant/tolerant cultivar, disease free seed (planting material)
sanitation, remove alternate host, optimize plant health
– Biological control methods
– Chemical control
Holistic approach

8. Common diseases of tomato
• Late blight (Phytophthora infestans)
– Infects Solanaceae plants
– High moisture, high RH and moderate temp. (10-21 ºC)
– Sever defoliation and fruit rot
– Introduced: on infected tomato transplants, infected
seed potatoes, volunteer plants, cull piles
• Produce millions of spores wind-borne and
spread into nearby fields

9. Needs 7-10 days between spore deposition and lesion
development (Infection)
Spore produced in 7-10 hours of
moist period
Late blight

10. Late blight

11. Late blight management
• Select resistant cultivars
• Transplant healthy seedlings
• Regularly monitor your fields
• Remove and destroy infected plants
• Measures to prevent further spread
– Keep foliage as dry as possible, avoid watering plants in the late
evening or early morning and do not over-fertilize.
• Fungicide spray (short interval once the disease is detected)

12. Late blight resistant tomato cultivars?

13. Late blight resistant cultivar trial, 2016
• 5 sites
• 11 cultivars
• No late blight incidence

14. Early blight (Alternaria solani)
– Infects leaves and fruits
– Reduces plant vigor
– Defoliated plants are subject to sunscald
– Infection:17 - 24ºC and extended leaf wetness
– Spore dispersal: water, wind, insects, other
animals, and machinery

15. Courtesy APS
Early blight

16. Early blight management
• Remove and destroy crop residue or plow residue
into the soil
• Crop rotation (3-4 years)
• Control volunteers and susceptible weeds
• Good air circulation
• Irrigate early in the day
• Proper nutrient management
• Minimize plant injury
• Use resistant or tolerant varieties
• Chemical/biological control

17. Powdery mildew (Oidium neolycopersici, Erysiphe lycopersici, Leveillula
taurica)

18. Powdery mildew
• Infection: warm, humid and fields under water stress
• Most common in high tunnel than in field tomato
Management
• The best management is prevention
• Select resistant varieties
• Fungicide/biocontrol
– Timing: no later than the first sign of disease
– good coverage

19. Leaf mold (Fulvia fulva syn. Cladosporium fulvum)
– Primarily a problem in greenhouses
– Can affect field tomatoes
– Most destructive (GH) during the fall, early winter,
spring when relative humidity is high and heating is
not continuous
– High relative humidity: fungus develops rapidly
• (RH ≥ 85%; 4º - 34ºC)
– If not controlled, results leaf death yield loss

20. Leaf mold (Fulvia fulva syn.
Cladosporium fulvum)

21. Leaf mold management
• Keep the RH <85%, reduce leaf moisture period
– Provide good air circulation
– Warmer night temperatures
– Avoid wetting the leaves
– Maintain temperatures 16º to 18ºC
– Adequate plant and row spacing (prevents excessive
shading)
• Select resistant cultivars (e.g. Deter Vs Indeterminate)
• Reduce primary inoculum (e.g. sanitation)
– Carefully remove and burn all plant debris

22. Cucurbits
• Powdery mildew (Podosphaera xanthii)
– Causes premature defoliation, affect yield and quality.
Management
• Sanitation
• Selecting PM-tolerant cultivars (if available)
• Fungicide spray

23. Downy mildew (Pseudoperonospora cubensis)
Lesions on leaves are often restricted by leaf veins, giving the lesion an angular or
square appearance
Management
-Use resistant varieties
-Monitoring (crops and weather forecasts)
-Site selection (air movement and without shading)
-Irrigation (avoid early morning or late in the day).
-Maintain nitrogen fertility

24. Alternaria leaf blight (Alternaria cucumerina)
• Avoid working when plants are wet
• Sanitation
– remove fallen leaves from the greenhouse
– Remove and destroy infected plants at the end of the season

25. Carrot Diseases
• Cavity spot and pythium root dieback(Pythium spp.)
• Sclerotinia rot (Sclerotinia sclerotiorum)
• Crater rot; Crown rot (Rhizoctonia)

26. Carrot Diseases
• Aster yellows
• Leaf blight (Alternaria dauci and Cercospora carotae)

27. Allium Diseases
Botrytis leaf blight
Downy mildew (Peronospora destructor)
• Stemphylium leaf blight
(S. vesicarium)
Botrytis neck rot
• Purple blotch (A. porri)

28. Basal plate rot/nematode
-Use clean seed (free of nematodes)
-Crop rotation

29. Cole crops Alternaria leaf spot (Alternaria sp.)
Management
• Minimize leaf wetness period
• Remove infected leaves and eliminate cull piles
• incorporate plant debris into the soil
• Crop rotation with non-host crops
• Fungicide/biocontrol spray
• Cool, wet and humid conditions favour
• Older, senescing plant parts are more susceptible
• Can spread by wind

30. Pathogens with wide host range
• Botrytis cinerea
• Sclerotinia sclerotiorum
• Damping off and root rot (Pythium spp., Fusarium spp.)

31. Lettuce
• Gray mould (Botrytis cinerea)
– Wide range (>100: trees, vegetables, ornamentals, weeds)
– Cool and humid conditions
– Infects damaged tissues
– Field lettuce: most serious in early spring and late fall

32. Botrytis gray mould (Botrytis cinerea)

33. Gray mould management
• Cultural practices
– Space plant adequately to provide good ventilation
– Proper fertilization (e.g. N and Ca levels)
– Sanitation: remove (eliminate) plant debris/cull piles
– Proper irrigation/watering
– GH: provide sufficient heat at night to prevent dew formation
• Chemical/biological control

34. Fungal plant pathogen
World wide distribution
Omnivorous >400 plant host species
Causes losses in the field and postharvest

35. Sclerotinia sclerotiorum
White mould, sclerotinia rot, pink rot,
cottony soft rot, drop, sclerotinia stem rot

36. Sclerotinia sclerotiorum
• Soilborne or airborne pathogen
• Survival structure: sclerotia
• Germination of sclerotium
 Myceliogenic (hyphal emergence)
• Infection by mycelium at or beneath the soil-line
 Carpogenic germination - produces apothecia
with ascospores
• Above ground infection
 Both Myceliogenic and Carpogenic

37. S. sclerotiorum (white mould) management
• Reduce viable sclerotia
– rotation (≥ 3yr) with non-host crops
– keep field free of weed
– discard infected plants from the field
– deep plowing to keep the sclerotia from soil surface
• During and after harvest
– do not mix infected with healthy crop (e.g. tomato)
– store harvested produce into clean bins
– proper storage temperature and ventilation
• Biological control

38. Damping-off and Root rots
• Pythium, Phytophthora, Rhizoctonia, Fusarium
• Seedlings affected at ground level and topple over
• Symptoms: seed decay, rotting roots and cankers on
the stem or lower petioles
• Damping-off: usually during the seedling stage
– Cool and wet springs
– Conditions that slow emergence and delay development
• Root rots: can affect at any growth stage
– Mostly warm, wet conditions

39. Damping-off management
• Use sterile soil-less mixture to grow seedlings
• Use clean (disease free seed)
• Care not to crack or shatter seeds
• Plant when soil and weather conditions are
favourable for vigorous crop development
• As soon as damping-off is detected, stop
watering for a while
– allow the soil to dry, but not completely dry
• Chemical/bio-control (e.g. drench application)

40. Biological Control Options
Organisms Product Name Targeted pests
(examples)
OMRI
(√)
Bacillus subtillus Serenade ASO
Serenade Max
Cease
Early/late blight in tomato & potato
Expanded label
√
√
√
Bacillus subtillis Rapsody ASO Powdery/downy mildew √
Bacillus subtillis Subtilex Damping-off and root rot in
greenhouse. Soil treatment
-
Coniothyrium
minitans
Contans WG Fungal diseases of some
greenhouse veg. Soil treatments
√
Gliocladium
catenulatum
Prestop Damping-off of greenhouse veg . and
herbs. Soil and foliar treatments.
√
Streptomyces
Strain K61
Mycostop Damping off, root and stem rot.
Soil and seed treatment
-
S. lydicus Actinovate Powdery mildew and gray mould √
Trichoderma
harzianum
Rootshield Rot diseases in greenhouse crops.
Soil treatment
√

41. Biopesticides
Active
Ingredients
Product
Name
Targeted pest (examples) OMRI (√)
Garlic Inflence LC & WP
Buran
Powdery mildew (PM) in greenhouse
(Tomato & Cucumber)
Powdery mildew cucumber
-
-
Extract of
Reynourtia
Regalia Maxx Inducing plant defense mechanisms
PM and bact. spot (pepper and tomato)
Gray mould (tomato)
√
Hydrogen
Peroxide
StorOx Fungicide/Bactericide: Fusarium tuber
rot, Bacterial soft rot, silver scurf,
Potato storage treatment
√
Lactic/Citric
acids
Cyclone
Tivano
Lacto-san
PM and DM greenhouse cucumbers
PM on cucurbits, bact. canker (tomato)
PM on cucurbits, bact. canker (tomato)
-
-
-
Saponins of
chenopodium
HeadsUp Fungicide/ Plant stimulant: Seed or pre-
transplant seedling foliar treatment
√

42. Biopesticides / Chemicals
Active
Ingredients
Product
Name
Targeted pest (examples) OMRI
(√)
Copper hydroxide Parasol WG
Kocide 2000 DF
Coppercide
Early/late blight in tomato &
potato (Prevention only)
√ (?)
-
-
Copper oxychloride Copper Spray Fungicide -
Hydrogen Peroxide StorOx Fusarium tuber rot, Bacterial soft
rot, silver scurf, post harvest
treatment
√
Calcium
polysulphide
Lime sulphur Insecticide/ miticide/fungicide -
Sulphur Kummulus DF
Bartlett Micro. S
UAP Micro. S
PM greenhouse, peppers, peas √
-
-
Potassium
bicarbonate
MilStop
Sirocco
PM on tomato, pepper, cucurbits √
-

43. www.gnb.ca/content/gnb/en/departments/10/agricultureResources

44. Resources

45. PMRA http://hc-sc.gc.ca/cps-spc/pest
Resources
http://perennia.ca/

46. English and French names of diseases used in the presentation
Insect Pests Cabbage maggot
Flea beetle
Mouche du chou
Altise
Tomato Late blight
Early blight
Powdery mildew
Leaf mold
Mildiou de la tomate
Brûlure alternarienne
Maladie du blanc
Moisissure olive
Cucurbits Powdery mildew
Downy mildew
Alternaria leaf blight
Maladie du blanc
Mildiou
Alternariose
Carrots Cavity spot
Sclerotinia rot
Crater and crown rot
Aster yellows
Leaf blight
Maladie de la tache
Moisissure blanche
Rhizoctone et rhizoctone commune
Jaunisse de l’ester
Brûlure des feuilles
Onions Botrytis leaf blight
Stemphylium leaf blight
Botrytis neck rot
Purple blotch
Downy mildew
Basal rot/nematode
Brûlure de la feuille
Brûlure stemphylienne
Pourriture du col
Tache pourpre
Mildiou
Fusariose /Nématode
Cole crops Alternaria leaf spot Alternariose
Pathogens with wide
host range
Botrytis (Gray mould)
Sclerotinia sclerotiorum
Damping-off and root rot
Botrytis (Moisissure grise)
Sclerotinia sclerotiorum
Fonte des semis et pourriture des racines