Downy mildew on lettuce.: Bremia lactucae; Lettuce downy mildew
Publication: PlantwisePlus Knowledge Bank
Pest Management Decision Guides
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Prevention
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Use resistant varieties if available
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Do not plant crop next to or downwind of infected fields since downy mildew spores spread via wind
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Keep fields free from weeds, particularly those in the daisy or sunflower family as these species are hosts of downy mildew. Removing weeds also improves aeration (the pathogen favours wet environments)
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Space plants far enough apart that leaves can dry quickly after watering or rains. Spacing should be 30-40 cm between rows, 15-20 cm between seedlings, depending on the variety (check recommendation provided with seeds)
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Avoid overhead irrigation to prevent leaves being wet for long periods of time
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Avoid irrigating crop at night when temperatures and cool and there is less evaporation of water off of the leaf surface
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Disinfect farm implements/tools with household bleach (1 part bleach to 1 part water) to avoid spreading the disease
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Rotate with crops not susceptible to the disease (crop not listed in the Monitoring column) for 2-3 years. The spores of the pathogen can survive in the soil for this long
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Avoid planting overlapping crops of lettuce if downy mildew symptoms are seen since it can spread from older to younger plants
Monitoring
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Additional relevant crops: globe artichoke, endive, chicory, ornamental spp.
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Downy mildew infects seedlings and mature plants
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Look out for:
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Light green/yellow round/angular spots on the top of leaves, particularly older leaves. Spots merge and turn brown, sometimes becoming soft and slimy
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Leaf spots may become infected by additional pathogens such as Botrytis cinerea (grey mold)
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White cotton-like growth develops on the underside of leaves in cool and humid conditions
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Monitor crop closely when weather is cool (less than 23°C) and damp (humidity is more then 85%).
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Consider taking action as soon as symptoms are seen
Direct Control
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During crop growth, remove any infected plants immediately and destroy by burning (if allowed in your area) or burying deeply (at least 1 m)
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After harvest, collect plant remains and burn or bury deeply (at least 1 m)
Indexing Terms
Descriptors
- burning
- cardoons
- chicory
- control
- crop density
- cultivars
- cultural control
- disease control
- disease resistance
- downy mildew
- endives
- extension
- fungal diseases
- globe artichokes
- lettuce downy mildew
- lettuces
- mildews
- monitoring
- ornamental plants
- pathogens
- pest management
- pests
- plant density
- plant disease control
- plant diseases
- plant pathogenic fungi
- plant pathogens
- rotations
- spacing
- varietal resistance
- varieties
- weed control
- weeds
Organism Descriptors
Identifiers
- climate smart agriculture
- artichokes
- cultivated varieties
- fungus
- ornamentals
- pest management decision guides
- phytopathogenic fungi
- phytopathogens
- plant-pathogenic fungi
- flaming
- resistance to disease
- advisory services
- extension activities
- crop rotation
- rotational cropping
- subsaharan Africa
- Abyssinia
- People's Republic of China
- Tanganyika
- Trinidad & Tobago
Geographical Locations
Broader Terms
- Peronosporaceae
- Peronosporales
- Oomycetes
- Oomycota
- Chromista
- eukaryotes
- Bremia
- Asteraceae
- Asterales
- eudicots
- angiosperms
- Spermatophyta
- plants
- Cichorium
- Cynara
- Cynara cardunculus
- Lactuca
- Africa
- ACP Countries
- East Africa
- Africa South of Sahara
- Least Developed Countries
- low Human Development Index countries
- low income countries
- APEC countries
- East Asia
- Asia
- high Human Development Index countries
- upper-middle income countries
- Anglophone Africa
- Commonwealth of Nations
- lower-middle income countries
- SADC Countries
- Caribbean Community
- high income countries
- Lesser Antilles
- Antilles
- Caribbean
- America
- medium Human Development Index countries
- South Asia
- very high Human Development Index countries
- Windward Islands
- West Africa
- Greater Antilles
- ASEAN Countries
- South East Asia
Information & Authors
Information
Published In
Pest Management Decision Guides
Pest Management Decision Guide: Green List
Copyright
© CABI 2017. This article is published under aCreative Commons Attribution-ShareAlike 4.0 International License (CC BY-SA 4.0)Published under a CC-BY-SA 4.0 licence
History
Issue publication date: 1 January 2017
Published online: 26 September 2017
Language
English
Authors
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