|Factors influencing efficacy of plastic shelters for control of bacterial blight of lilac
|Year of Publication
|Stockwell, V, Shaffer, BT, Henkels, MD, Pscheidt, J, Loper, JE
Plastic shelters are thought to manage bacterial blight by protecting plants from rain and/or frost. In February to April 2008 and 2009, we studied the contribution of frost protection to efficacy of this cultural control practice. Lilacs in 1-gallon pots were exposed to 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. Freezing events were frequent (>20/season), but average low air temperatures did not differ significantly inside vs. outside of shelters. Plants with no shelters were exposed to frequent rain, whereas, plants under shelters remained dry. Populations of P. syringae exceeded 10 E6 cfu/leaf on plants with no shelters vs. <10 E2 cfu/leaf on plants under shelters. Bacterial blight symptoms were observed on 55% to 60% of the leaves of plants with no shelters vs. <5% of leaves of plants under 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 efficacy. These results demonstrate that lilacs grown under plastic shelters exhibit few symptoms of bacterial blight and support low population sizes of P. syringae. Limiting free moisture on leaf surfaces appears to be important in the disease control provided by plastic shelters.