Situation of pitch canker (Gibberella circinata) in California
A review by Gordon et al. (2001) presents in details the situation of pitch canker (Gibberella circinata – EPPO Alert List) in California, US. Pitch canker was first described in southeastern USA in 1946 where it remains a chronic problem in pine plantations and seed orchards. In California, it was found in the mid-1980s. Surveys have showed that G. circinata is currently widespread in coastal California, near San Francisco and in Alameda, Santa Cruz, Monterey, San Luis Obispo, Santa Barbara counties. It is also found in Christmas tree farms in Los Angeles and San Diego counties. In California, Monterey pines (Pinus radiata) severely affected by the disease are found in nurseries, Christmas-tree production farms, landscape plantings and also in native forests (Ano Nuevo, Monterey peninsula and Cambria). In California, G. circinata was probably introduced from southeastern USA through infected seeds or nursery material, and spread on this type of material. Nurseries producing P. radiata sold seedlings to Christmas-tree production farms. The availability of infected (but asymptomatic) trees at “choose and cut” farms then provided a ready pathway for moving the pathogen in California. In addition, once pitch canker has killed large trees, their removal, usually as logs for firewood, offered other possibilities for spread. In California, unlike southeastern USA, insects play a major role in disease epidemiology, as vectors (e.g. Conophthorus radiatae, Ernobius punctulatus, Ips paraconfusus, Pityophthorus setosus) or wounding agents (e.g. Aphrophora canadensis). In California, essentially P. radiata is affected by G. circinata, but P. attenuata and P. muricata are also attacked. Glasshouse tests have shown that the following pine species are susceptible to the fungus: P. contorta, P. coulteri, P. halepensis, P. jeffreyi, P. lambertiana, P. ponderosa and P. sabiniana. In these trials, P. thunbergiana, P. pinea, and P. canariensis were not susceptible. Control of G. circinata is difficult, particularly in natural forests.
Sources
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Gordon, T.R.; Storer, A.J.; Wood, D.L. (2001) The pitch canker epidemics in California.
Plant Disease, 85(11), 1128-1139.
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