The Effect of Plastic Mulch and Forced Heated Air on Botrytis cinerea on Geranium Stock Plants in a Research Greenhouse. M. K. Hausbeck, Former Graduate Research Assistant, The Pennsylvania State University, University Park 16802. S. P. Pennypacker, Professor, and R. E. Stevenson, Senior Research Assistant, The Pennsylvania State University, University Park 16802. Plant Dis. 80:170-173. Accepted for publication 16 November 1995. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0170.

Plastic mulch and intervals of forced heated air were incorporated among geranium (Pelargonium ´ hortorum) stock plants within a research greenhouse to limit stem blight caused by Botrytis cinerea and reduce inoculum produced on necrotic lower leaves of mature stock plants. The area under the leaf blight disease progress curve (AUDPC) revealed that the incidence of sporulating B. cinerea on necrotic lower leaves of mature stock plants was significantly decreased compared with that on the control for all treatments including (i) white plastic mulch on top of the pots, (ii) heated air forced into the plant canopy during 2200 to 0600 h, and (iii) a combination of plastic mulch and forced heated air. The AUDPC data indicated that the combination of plastic mulch and forced heated air limited the incidence of sporulating B. cinerea on the lower necrotic leaves of stock plants significantly more than did the individual treatments. Forced heated air limited the incidence of sporulating B. cinerea on the lower necrotic leaves of stock plants significantly more than did the plastic mulch. Similarly, fresh and dry weights of necrotic leaves with sporulating B. cinerea indicated that the combination of plastic mulch and forced heated air was most effective in limiting the incidence of necrotic leaves with sporulating B. cinerea. According to these data, forced heated air among stock plants effectively reduced the incidence of sporulating B. cinerea on necrotic leaves compared with the plastic mulch and control. Stem blight caused by B. cinerea occurred on all inoculated stems and disease progression was not reduced regardless of treatment