White tip disease

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Phytophthora
White tip disease
Leek White tip disease Phytophthora porri.jpg
Scientific Classification
Domain: Eukaryota
Kingdom: Chromalveolata
Phylum: Heterokontophyta
Class: Oomycetes
Order: Peronosporales
Family: Pythiaceae
Genus: Phytophthora
Species: Phytophthora porri
Risk period
J F M A M J J A S O N D
Synonyms

White tip
White tip disease

White tip disease of leeks (Phytophthora porri) mainly attacks the crop from the end of July until September-December in humid conditions. Heavy rain, causing the soil to splash onto the foliage, can lead to serious infection. Onions are less often infected by the pathogen but seedling infection can occur.[1]

Symptoms[edit]

Symptoms are a white die back of the leaf tips, white patches surrounded by a water-soaked zone appear on other parts of the leaf and stem, and stunted growth. These areas become dry and papery. Lesions are most often restricted to leaf tips, but may also occur on the margins, centre or base of leaves Infected leaves look watery, thin and papery, eventually they rot away.[2]

Control[edit]

The pathogen survives as oospores in the soil and crop rotation is therefore the main method of control. Affected debris should not be returned to the land. Because the pathogen needs wet periods for establishment on the plant, crops should be grown in less humid areas and be irrigated only when really necessary. In many regions, the infection level rarely reaches the economic threshold, but yield losses up to 50% have been reported in some countries. Metalaxyl-resistant strains have been detected.[1] Badly infected leeks should be removed and destroyed, and the remainder sprayed fortnightly with a fungicide until all the white patches disappear.[2]

Chemical[edit]

Sprays: chlorothalonil, copper oxychloride, mancozeb, metalaxyl, propamocarb, thiram.[1]

References[edit]

  1. a b c (2000). Guidelines on Good Plant Protection Practice - Allium Crops. European and Mediterranean Plant Protection Organization. 1, rue Le Nôtre, 75016 Paris, France. p.5.
  2. a b White Tip Disease (Phytophthora porri). Garden Action. Retrieved: 2011-02-04.