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Effects of branch size and pathogen virulence on canker development and branch mortality

Davelos Baines, A., Fulbright, D.W., Jarosz, A.M.
Acta horticulturae 2014 no.1019 pp. 23-29
Castanea dentata, Cryphonectria parasitica, biological control, branches, chestnuts, double-stranded RNA, fungi, mortality, pathogens, trees, virulence, Michigan
Effective biological control using dsRNA requires that chestnuts infected with dsRNA-containing strains of the chestnut blight fungus (Cryphonectria parasitica) have higher survival than trees infected with dsRNA-free strains. The influence of branch size on canker development and branch mortality was investigated in an American chestnut stand in Michigan. Comparisons among cankers initiated naturally (after wounding), with dsRNA-free and dsRNA-containing C. parasitica revealed that larger branches are more likely to have callused cankers than smaller branches. Larger branches also are more likely to survive independent of the presence/absence of dsRNA. The presence of dsRNA reduces canker growth rates and may delay mortality of larger branches but has no impact on survival of small branches (<2 cm in diameter). These results suggest that inoculating larger branches and trees with dsRNA-containing C. parasitica may produce effective biological control while the survival of smaller individuals will not be enhanced by treatment.