Test of copper fungicides for fire blight and primary apple scab control on Nittany apple, 2012

摘要

Fourteen treatments involving an early season copper application were tested for fire blight blossom blight, early season scab control, and potential for fruit russetting caused by copper residue. The test strategies were1) to apply copper treatmentsat delayed dormant (approximately 1/2”-greentip) with and without a follow-up streptomycin (FireWall) application at bloom and 2) to spray-inoculate blossom clusters in the tops of the test trees to promote secondary infection throughout the tree. The test was conducted on 31-yr-old trees with a 28-ft row spacing in a randomized block design with four single-tree replicates. Copper treatments were applied dilute to run-off on 22 Mar, (Application #1, Trts #2-14; 1/4”-green- tight cluster). On 2 Apr, at early bloom, four groups of blossoms in the top of each tree were inoculated by spraying a suspension of E. amylovora(1X10~6 cfu/ml) in each inoculation site. On 3 Apr, follow-up streptomycin was applied at pink-30% bloom to treatments #1, 3, 5, 7, 9,11, 13, and 14. After a period of cool weather, which was unfavorable for natural fire blight development, a water spray was applied to the test orchard to increase the potential for infection in the absence of natural wetting during warmer weather at late bloom-petal fall 16 Apr. This was applied by airblast at 100 gal per acre. Scab and cedar-apple rust developed from inoculum naturally present in the test area. Fire blight strikes were counted on 21 May. Foliar fungal diseases were assessed on ten flower cluster leaf sets per tree on 23 May and on the first ten leaves of ten shoots per tree on 22 Aug. Fruit data are based on 25-fruit sample taken and rated on 23 Aug. Late season fungicides, applied to all but non-treated trees, included Captan 80WDG30 oz + Ziram 3 lb/A applied 10 Jul, 26 Jul, 2 Aug, and 15 Aug and Pristine 14.5 oz + Captan 80WDG 30 oz/A applied 29 Aug. Maintenance materials applied to the entire test block with the same equipment included Asana XL + oil, Assail, Altacor, Calypso,Delegate, Imidan, Lannate LV, and Provado. Percentage data were converted by the square root arcsin transformation for statistical analysis (mean separation Waller-Duncan t-test).