Submitted to: International Symposium on Microbiology of Aerial Plant Surfaces
Publication Type: Abstract Only
Publication Acceptance Date: June 18, 2010
Publication Date: August 15, 2010
Citation: Stockwell, V., Shaffer, B.T., Henkels, M.D., Pscheidt, J.W., Loper, J.E. 2010. Management of bacterial blight of lilac caused by Pseudomonas syringae by growing plants under plastic shelters. International Symposium on Microbiology of Aerial Plant Surfaces Program Book.p.80. Technical Abstract: Pseudomonas syringae pv. syringae causes some of the most economically-important bacterial diseases affecting woody perennials grown by the nursery industry in the Pacific Northwest of the United States. In this study, we evaluated a cultural control practice, placement of plants in plastic shelters, for management of bacterial blight of lilac (Syringa vulgaris ‘Angel White’). Because plastic shelters are thought to manage disease by protecting plants from rain and/or frost, we monitored environmental conditions inside and outside of experimental shelters. To determine the contribution of frost protection to the efficacy of this cultural control practice, the experiment included four treatments: 1) plants grown with no shelters, 2) plants grown under plastic shelters, 3) plants grown with no shelters, but placed under shelters when frost was predicted, and 4) plants grown under shelters, which were removed when frost was predicted. Plastic shelters provided excellent management of bacterial blight of lilac. In 2008 and 2009, necrotic spots symptomatic of the disease were observed on 55% to 60% of the leaves of plants grown with no shelters vs. <5% of leaves of plants grown under shelters. At the end of the experiments, epiphytic populations of P. syringae exceeded 10 E6 cfu/leaf for plants grown with no shelters vs. <10 E2 cfu/leaf for plants grown under shelters. There were 29 freezing events in 2008 and 22 freezing events in 2009 but average low air temperatures did not differ significantly inside vs. outside of the experimental shelters. Disease severity was similar between treatments 1 and 3, and between treatments 2 and 4, indicating that cover during frost events alone was not a major factor influencing the efficacy of the experimental shelters. Limiting free moisture on leaf surfaces appears to be an important component of the disease control provided by the experimental shelters evaluated in this study.