The Perfect Stage of Cercospora Magnoliae

Abstract

Cercospora imagnoliae Ell. & Harkn. emended Hodges & Haasis causes a common leaf spot disease of Magnolia virginiana L. and M. grandiflora L. throughout the southeastern United States (4, 8). In the spring of 1962, a species of Mycosphaerella was found near Patrick, S. C., on dead leaves of M. virginiana which had overwintered on the ground. This fungus was found also at several locations in North Carolina and South Carolina and was present only on leaves which showed the characteristic symptoms of Cercospora leaf spot. Single ascospore isolates from the Mycosphaerella produced cultures identical to those of C. mnagnoliae made previously from single conidia. Inoculations made on seedlings of M. grandiflora and M. virginiana with conidia from single ascospore cultures using techniques described previously (4) produced typical symptoms of Cercospora leaf spot. The same Mycosphaerella was found sparingly on badly decomposed leaves of M. grandiflora infected with C. magnoliae, but attempts to make single ascospore isolates from this host were unsuccessful. Type material of several species of Mycosphaerella and closely related fungi on Magnolia spp. were obtained from several herbaria for comparison with the perfect stage of C. magnoliae. The latter fungus was distinctly different from any previously described on magnolia and is described herein as a new species with the following characteristics: