White Tip - Leeks
Phytopthora porri
Pathogen
Fungus
Hosts
Leeks
Can also be found on onions and other Allium spp
Symptoms
Can be first seen in late summer (end July) but more readily found in late autumn. The first symptoms are yellowing lesions at the leaf tips which become dry, bleached and white. As the lesions develop they can coalesce causing dieback on large areas of leaf tissue. On close inspection water soaked regions can be observed between the lesion and healthy tissue.
Development
White tip survives in the soil as oospores for periods of 3 years or more. These germinate to form sporangia (spore containing bodies) which release spores to infect host plants. Established lesions produce further oospores to distribute the disease more widely.
Favourable Factors
Develops in cool, humid, wet conditions.
Importance
An important disease of leeks in Western Europe and the UK. Has become more of a problem as leek production increases and effective fungicide options decrease.
Control
Rotation, 3 years or more.
A limited range of fungicides are available for white tip reduction.
Effect on leek plant (Photo D. Pop)
Close up of leaf symoptom. Note water soaked area surrounding edge of leision. (Photo D. Pop)
Severe crop infection (Photo D. Pop)
