Leaves, petioles or fruits with spots should be washed in
tap water and then rinsed with distilled water and blotted
dry or lightly surface disinfected (e.g. by wiping with 70%
ethanol). Small pieces of tissue bordering necrotic lesions
should be crushed in one or two drops of sterile physiological
saline (SPS = 0.85% NaCl in distilled water) or 1%
peptone or 10 mM PBS.