Two methods were used to estimate disease
severity caused by Cephaleuros spp. First,
the most seriously affected host leaves were
assessed by estimating the percentage of their
upper leaf surfaces covered with algae: light
«5%), moderate (6-25%), or heavy (>25%).
Disease severity was also measured for mature
thalli from a nonrandom sample of hosts using
a four-point necrosis index: (0) no necrosis;
(1) superficial necrosis of the cell layer
beneath the algal thallus, with or without tissue
hyperplasia; (2) necrosis of > 1 cell layer
but not full leaf thickness, with or without
tissue hyperplasia, erosion, or suberin formation;
and (3) necrosis from upper to lower
leaf surface, including "shot-hole" symptoms.
Damage was assessed under a stereoscope by
dissecting fresh and dried lesions with a scalpel