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POSTERS: Biological control

Understanding Niche Clearing as a Means to Improve Establishment and Efficacy of Applied Bacterial Biological Controls
Joseph Doherty - University of Maryland. Joseph Roberts- University of Maryland

Introduced biological control agents (BCAs) are available for use in turf but remain under-utilized due to inconsistent efficacy in the field. By disrupting existing microbial communities, it may be possible to improve the survival and efficacy of introduced BCAs. To better understand introduced BCA survival, we examined applications on perennial ryegrass (Lolium perenne L. cv . “Express II”) maintained in a greenhouse. The trial utilized a split-split plot design with a factorial treatment arrangement to assess combinations of hydrogen peroxide with BCAs (Bacillus subtilis QST-713, B. subtilis Exp. W9, Pseudomonas chlororaphis AFS009). Five weeks after trial initiation, half of the pots were inoculated with Rhizoctonia solani L. Foliage samples were collected at 0, 2, 4, 7, 10, and 13 days post application for 4 sequential applications. Leaf washings were plated onto selective media to assess bacterial populations (Pseudomonas spp., Bacillus spp., and general bacteria). While brown patch progressed rapidly across all inoculated pots, pots treated with hydrogen peroxide survived 48 h longer. The first application of B. subtilis QST-713 significantly increased general bacterial populations compared to all other treatments, 0 days after treatment (DAT). Higher Bacillus and Pseudomonas populations were observed in hydrogen peroxide treated pots, 4 and 7 days after the third application. Although populations of BCAs were not high enough to reduce brown patch on this date. Initial data show hydrogen peroxide may help establishment of BCAs, but additional research is needed.