Early season disease control by combined fungicides on Red Delicious, Golden Delicious, and Rome apples, 2009.

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. Treatments were evaluated on 21-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 2008 to allow powdery mildew inoculum to stabilize in the 2009 test trees. Unused border Rome trees were uniformly treated with Rally 1 oz per 100 gal on 15 May and 29 May to suppress disease pressure for 2010. Dilute treatments were applied to the point of runoff with a single nozzle handgun at 400 psi as follows: App. #1= 9 Apr, (Trts. 1 & 2 only, Rome, ” greentip, Red & Golden Delicious, open cluster); #2=16 Apr (all treatments, Rome, tight cluster; Golden Delicious tight -open cluster; Red Delicious, pink); #3= 24 Apr, (Rome, pink; G. Del., 30% bloom; R. Del., full bloom); #4= 5 May, (petal fall,); and #5-11 (1st–7th covers) on 19 May, 2 Jun, 16 Jun, 30 Jun, 14 Jul, 30 Jul, and 20 Aug. Cover sprays (#10-11) were applied uniformly to all treatments by dilute airblast instead of by handgun on 30 Jul and 20 Aug. Maintenance sprays, applied separately to the entire test block with a commercial airblast sprayer, included Supracide, Assail, Imidan, Provado, Intrepid, Lannate LV, Delegate, Calypso, and Altacor. Inoculum over each Golden Delicious test tree included cedar rust galls, placed 3, 8, and 28 Apr; and wild blackberry canes with the sooty blotch and flyspeck fungi, and bitter rot mummies, placed 28 Apr. Other diseases developed from inoculum naturally present in the test area, including cedar-apple rust inoculum from red cedars in the vicinity. Foliar data represent averages of counts of 10 terminal shoots from each of four single-tree reps on 19 Jun (Golden) or 20 Jul (Rome), or 10 Red Delicious spur cluster leaf sets on 4 Aug. Postharvest fruit counts are means of 25-fruit samples picked from each of four single-tree reps on 22 Sep (Red Delicious and Golden Delicious) or 28 Sep (Rome), placed in cold storage at 4degC, and rated after 16 to 30 days in cold storage. Following initial evaluation, fruit were incubated at a mean temperature of 70degF for 17 to 20 days before final storage rot assessment. Percentage data were converted by the square root arcsin transformation for statistical analysis.