Effects of Inoculum Density and Wounding on Stem Infection of Three E astern US Forest Species by P hytophthora ramorum

• Published in: Journal of phytopathology Vol. 162; no. 10; pp. 683 - 689
• Main Authors: Tooley, Paul W., Browning, Marsha, Leighty, Robert M.
• Format: Journal Article
• Language: English
• Published: 01-10-2014
• ISSN: 0931-1785; 1439-0434
• DOI: 10.1111/jph.12251

Abstract
Seedlings of three
E
astern
US
forest species
Q
uercus rubra
(northern red oak),
Q
uercus prinus
(chestnut oak) and
A
cer rubrum
(red maple) were inoculated by applying
P
hytophthora ramorum
sporangia to stems at different inoculum densities with and without wounding. Disease occurred in all treatments involving wounds, and no disease was observed in unwounded treatments. Younger seedlings (2–3 years old) did not differ significantly from older seedlings (5–6 years old) in disease incidence, but older seedlings sustained smaller lesions compared with younger seedlings. For both old and young seedlings, disease on wounded stems was observed down to the lowest sporangia concentration utilized (500 sporangia/ml for old seedlings and 100 sporangia/ml for young seedlings). The results show that in the presence of wounding, even very low sporangia concentrations can result in disease, and further suggest that wounding caused by insects and other factors may play an important role in
P
. ramorum
epidemiology in forest environments.