Main content area

Infection without wounding and symptomless shoot colonization of Pinus radiata by Fusarium circinatum, the cause of pitch canker

Swett, C. L, Reynolds, G. J., Gordon, T. R.
Forest pathology 2018 v.48 no.3 pp. e12422
Fusarium circinatum, Pinus radiata, branches, death, girdling, hyphae, pathogens, seedlings, surveys, trees, California
SUMMARY: Fusarium circinatum is widely regarded as a necrotrophic pathogen of pines that infects shoot tissue through mechanical or insect‐mediated wounds, causing girdling lesions that result in death of infected branches. However, in the study reported here, F. circinatum colonized 100% of seedling stems and 70% of mature tree branches that were not wounded. Hyphae were observed beneath the epidermis of non‐wounded shoot tissue within 14 days following inoculation. In both seedlings and branches, most infections of non‐wounded tissue did not induce symptoms for the duration of the trial (seven to eight weeks). In surveys of native Pinus radiata stands in California, F. circinatum was recovered from 7.5% to 100% of healthy‐looking seedlings (2–3 years old) across three of the four stands surveyed. These results suggest that wounding is not a requirement for shoot infection under all circumstances and that F. circinatum can grow within shoot tissue without causing symptoms.