Impatiens balsamina: A Natural Host of Sphaerotheca fuliginea. Mohd. Akram, Mycology and Plant Pathology Laboratories, Department of Botany, Aligarh Muslim University, Aligarh (Uttar Pradesh) 202002 India.. S. Iqbal Husain, Mycology and Plant Pathology Laboratories, Department of Botany, Aligarh Muslim University, Aligarh (Uttar Pradesh) 202002 India. Plant Dis. 79:754. Accepted for publication 2 May 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0754A.
Powdery mildew was observed on leaves, stems, calyx, and fruits of balsam (Impatiens balsamina L.) plants grown in Aligarh, Uttar Pradesh. Both surfaces of a leaf may be infected, but usually the powdery white appearance of the fungus was more abundant on the upper leaf surface. The pathogen was also observed on cvs. Avoidefiance and Krimson Monarch from the areas of Etawah, Uttar Pradesh, each geographically separated by at least 170 km (100 miles). White powdery mildew pustules developed on the upper surface of the leaf and were more frequent on mature than on young leaves. Individual lesions were elliptical but sometimes coalesced to cover large areas of the leaf surface. Cleistothecia were not found. Conidia were produced in chains on unbranched conidiophores. Conidia were ellipsoidal and measured 22.5 to 33.0 ?m by 11.0 to 22.5 μm. They were thin walled, smooth, and colorless, and each contained 3 to 8 well-developed fibrosin bodies as well as 5 to 12 vacuoles. Conidia germinated on dry glass slides and developed forked germ tubes without well-differentiated appressoria. On the basis of condial characters, the fungus was identified as Sphaerotheca fuliginea (Schfech-tend.:Fr.) Pollacci. Colonized leaves were gently shaken to dislodge the conidia over healthy Avoidefiance plants grown in the greenhouse, and mildew colonies developed within 8 days. Weather conditions were conducive to development of powdery mildew during the 1993 growing season, with mean maximum temperatures of 24, 28, and 26°C and relative humidity of 82.5 to 95.0% during September, October, and November, respectively. Reports of balsam as a host of powdery mildew have been made by researchers in various countries (1,2). This is the first report of powdery mildew of balsam in Uttar Pradesh stale.References: (1) F. L. Tai. Bull Torrey Bot. Club 73:108, 1946 (2) G. Lim and L Koh. Trans. Br. Mycol. Soc. 77:438, 1981.