White tip

Phytophthora porri


The first observable symptom is a yellowing of the leaf tips; later they become bleached and white and die rapidly, hence the term 'white tip'. This infection results from direct contact between infested soil and leaf tips. Leaves are often distorted and twisted. Infection progresses from the tip to about half-way down the leaf. Leaf spots are initially water-soaked but turn white and crisp. Spots are surrounded by a green, transparent, water-soaked region. Many infections also start in the water basin that is usually present near the leaf axils. Lesions will appear at some distance above this water basin because of leaf growth during the incubation period. Both young and old plants are affected, and severe infection results in rotting off of leaves at the soil level.

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