Evaluating OxiDate 2.0 and copper to mitigate the blossom blight phase of fire blight on 'Buckeye Gala' apple trees in Pennsylvania, 2018

摘要

Bactericide programs including OxiDate 2.0 and copper were compared against the standard (streptomycin) for the control of the blossom blight phase of fire blight, caused by Erwinia amylovora. The efficacy trials were conducted in an orchard with 11-year-old semi-dwarf 'Buckeye Gala' apple cultivar on M.7 rootstocks. Single-tree treatments were arranged in a randomized complete block with 4 replications. Before the first treatment was applied, three to four branches were selected per tree, such thatat least 50 blossom clusters were available. Fire blight treatments were applied early in the morning on 4 May at 100% bloom using a backpack mistblower until run-off at a rate of 100 gal/A. Blossom clusters were inoculated mid-afternoon on the same dayof treatment (4 May) using a spray bottle containing a bacterial suspension of 107 E. amylovora cells/ml using the Ea273 strain. For two treatments, blossoms were inoculated in the morning, followed by treatment applications in the afternoon. This was tobetter understand the efficacy of certain products. We also had fungicide trials occurring within this apple block concurrently; however, they did not interfere with our fire blight trial. A standard insecticide maintenance program was applied to the entire orchard with an airblast sprayer. Weather data was recorded with a Decagon weather monitoring system and fire blight infection periods were determined using MaryBlyt. Rainfall totals for April through August were 5.72, 6.42, 5.06, 11.46, and 9.74 in., respectively. Blossom clusters were rated during the third week of May. Blossom clusters were rated infected if at least one blossom was dead. Shoot blight strikes were counted in mid-July. To evaluate fruit russet severity, 25 fruit per tree/treatment/replicate (total: 100 fruit/treatment) were evaluated. Severity was evaluated using a russet rating scale from 0 - 6 (0: 0%; 1: 1-3%; 2: 4-8%; 3: 9-15%; 4: 16-25%; 5: 26-45%; 6: > 45%), then transformed to percent area covered with russet on the fruit.Mean percent incidence of disease and fruit russet was calculated, as well as the average number of shoot strikes per tree. Data were analyzed using analysis of variance and the Fisher's Protected LSD Test determined the mean separation.