Fig 2. Petiole rating using a 1–5 scale.

1—No pathogen colonies visible on petioles. 2—A small number of colonies limited to the base of some petioles. 3—Colonies on nearly all petioles near the base, and extending halfway up the petiole. 4—Colonies on all petioles, extending the full length of the petiole to the leaf blade, but lacking colony density of fully susceptible cultivars, especially near the leaf blade. 5—All petioles covered with pathogen colonies from petiole base to the leaf blade at high density; most individual colonies have coalesced into larger colonies.