Full season disease management by fungicide mixtures and rotations on Red Delicious, Golden Delicious, and Rome apples, 2012

摘要

Nine treatments, aimed primarily at early season and early summer diseases, were compared for season-long fungal disease control and fruit finish effects on three apple cultivars: Red Delicious, Golden Delicious, and Rome. Sterol inhibitor (SI) and Quinone outside inhibitor (QoI) fungicide effectiveness has been declining in both powdery mildew and scab. The SI fungicide in this test is Rally and QoI fungicides include trifloxystrobin in Flint and pyraclostrobin in Merivon. Treatments were evaluatedon 23-yr-old, three-cultivar tree sets in a four-replicate randomized block design. The Rome trees used in the test had not been treated in 2011 to allow powdery mildew inoculum to stabilize in the 2012 test trees. Fungicide treatments were applied to the point of runoff with a single nozzle handgun at 450 psi as follows: 30 Mar, Trt #1-9 (Rally on # 9, pink-king bloom); 13 Apr, Trt #1-9 (No Rally on #9, Rome-pink, Golden Delicious pink-bloom, Red Delicious-petal fall); 25 Apr, (Rally on #9, Rome-late petal fall); 9 May, (1st Cover, 1C; Trt #1-9, Rally on #9); 24 May (3rd Cover, 3C; Trt #1-9, no Rally on #9); 4th-8th Covers (4C-8C) on 7 Jun, 20 Jun, 11 Jul, 27 Jul, 15 Aug, respectively. Inoculum placed over each Golden Delicious test tree included: cedar rust galls placed 22 Mar, and wild blackberry canes with the sooty blotch and flyspeck fungi and bitter rot mummies placed 10 Apr. Other diseases developed from inoculum naturally present in the test area, including cedar-apple rust inoculum from redcedars in the vicinity. Insecticide and fruit thinning sprays, applied separately to the entire test block with a commercial airblast sprayer, included: Asana XL + oil, Altacor, Assail, Calypso, Imidan, Lannate LV, Provado, Delegate, and Retain + Fruitone + Silwet. Foliar data represent averages of counts of ten cluster leaf sets or shoots per Golden Delicious tree 8 May and Red Delicious cluster leaves 11 May, or ten terminal shoots 25 Jun (Golden Delicious) and 23 Jul (Rome). Fruit ratings are means of 25-fruit samples picked from each of four single-tree reps 11 Sep (Golden Delicious), 16 Sep (Red Del.) or 26 Sep (Rome), placed in cold storage at 39°F and rated after 37 days (Rome), 31 days (Golden Del.), and 32 days cold storage (Red Delicious). After initial fruit evaluation, fruit were incubated at ambient warm temperatures 67-88°F before final storage rot assessment. Percentage data were converted by the square root arcsin transformation for statistical analysis using Waller-Duncan K-ratio t-test (p=0.05).