PESTS AND DISEASES OF FORESTRY IN NEW ZEALAND
Flagging of Plane
ACROSS THE PATHOLOGY BENCH- FLAGGING OF PLANE
From Forest Health News 103, Decermber 2000
Flagging of shoots, twigs and small branches is a regular spring feature of plane trees growing in the urban environment throughout many parts of New Zealand. The fungus Apiognomonia veneta causes the disease, which is commonly known as plane anthracnose. The fungus affects the trees in several different ways. Buds that were infected during the winter and early spring will often die before opening. Once the spring growth begins a canker develops around the base of the bud and if the lesion girdles the twig, dieback of that twig beyond the lesion will follow. Usually the cankers are only annual, however some may continue to expand for a second year. Shoot blight, in which the buds begin to open but die back before flushing is complete is often the most visible manifestation of this disease, with dead leaves and drooping shoots over the entire crown in cases of severe infection. Leaf infection can happen at any time during the summer, the infected leaves developing brown dead zones bordering the main veins. Cankers form occasionally on the main stems or branches of young, highly susceptible trees. Attacks of anthracnose can, on occasion, be spectacular but severe outbreaks are relatively rare. Infected trees usually recover but can remain very thin in the crown. London plane (Platanus x acerifolia) and sycamore (P. occidentalis) are susceptible whereas the oriental plane (P. orientalis) is regarded as largely resistant.
(Margaret Dick, Forest Research)
