Downy mildew | |
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A grape leaf showing downy mildew and powdery mildew | |
Scientific Classification | |
Kingdom: | Chromalveolata |
Phylum: | Heterokontophyta |
Class: | Oomycetes |
Order: | Peronosporales |
Family: | Peronosporaceae |
Downy mildew refers to any of several types of oomycete microbes of the Peronosporaceae family that are a particular problem for growers of brassicas, grapes and vine-type vegetables.
Cucurbit downy mildew (caused by Pseudoperonospora cubensis) is specific to cucurbits (e.g. pumpkin, squash, courgette). The disease is one of the most important diseases of cucurbits worldwide.
A serious disease in cool, damp seasons.
Symptoms[]
The initial symptoms of downy mildew appear on leaves as light green to yellow spots, then as it develops it becomes a downy grey mould. Leaves slowly die back and shrivel from the tips.[1] Onion bulbs infected become soft and are not suitable for storage.
Treatment[]
None. Should the disease be confirmed on site, immediately dispose of diseased material in sealed bags or bins and arrange for it to be destroyed.[2]
Prevention[]
Good practice[2]:
- Try to ensure any starting plant material is disease free.
- Provide good air circulation and ventilation in glasshouses.
- Try to avoid long periods of high humidity and leaf wetness.
- Avoid watering crops late in the day.
- Apply a routine preventative fungicide programme to minimise disease risk, especially during periods when environmental conditions are favourable for downy mildew infection.
- Practice good nursery hygiene by cleaning up plant debris between crops and at the end of the season and use appropriate disinfectants.
Examples[]
References[]
- ↑ Hessayon, D.G. (2009). The Vegetable & Herb Expert. Transworld Publishers, London. p. 75. ISBN 9780903505468
- ↑ a b McPherson, M. and Brough, W. (2009) "Good Horticultural Practice for the Prevention and Control of Impatiens Downy Mildew (Plasmopara obducens)". Agriculture and Horticultural Development Board. Retrieved 2010-07-17.
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Brassica troubles |
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Diseases | Anthracnose · Bacterial soft rot · Black leaf spot · Black rot · Brassica dark leaf spot · Club root · Downey mildew · Grey leaf spot (Brassica) · Turnip mosaic virus · Sclerotinia rot · White leaf spot · White leaf spot (Brassica) · White rust · Wire stem |
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Basil · Lavender · Lemon balm · Marjoram · Mint · Oregano · Rosemary · Sage · Savory · Thyme | |
Adverse conditions | Bolting |
Diseases | Downy mildew · Fusarium wilt · Grey mould · Powdery mildew · Rhizoctonia solani · Rust · Septoria leaf spot of lemon balm · Verticillium wilt |
Pests | Aphid · Cabbage whitefly · Capsid bug · Celery fly · Leaf miner · Leafhopper · Red spider mite · Shore fly · Silver Y moth · Slug |
Raspberry troubles |
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Diseases | Anthracnose · Cane and leaf rust · Cercosporella leaf spot · Downy mildew · Arabis mosaic virus · Orange rust · Phytophthora root rot of raspberry · Raspberry leaf curl virus · Raspberry leaf spot · Raspberry ringspot virus · Rose scale · Septoria leaf spot of blackberry · Spur blight |
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