Effectiveness of ProPhyt used alone or with other fungicides to control summer diseases of apples, 2007

摘要

A 3x4 factorial design was used to compare effectiveness of Captan, Topsin M, and Pristine applied either alone or with two different rates of ProPhyt. The commercial standard of Topsin M 4 oz/100 gal plus Captan 80WDG 10 oz/100 gal was included as a13th treatment but was not included in the statistical analysis. All treatments were replicated four times in three-tree plots that contained one tree of each cultivar. The test orchard was planted in 2001 and contained Cameo trees on Bud.9 rootstocks and Honeycrisp and Royal Court trees on EMLA.111 rootstocks with M.9 interstems. Trees in this orchard were maintained during the early part of the season using standard combinations of DMI and mancozeb fungicides applied with an airblast sprayer. The lastfungicide spray applied to the entire block was on 17 May and consisted of 2.2 lb/A Dithane, 3.7 oz/A Nova, 9 oz/A FireWall, 16 fl oz/A Regulaid. Test treatments were applied using a high-pressure handgun at 250 psi on 7 Jun, 3 Jul, 23 Jul, and 14 Aug.Fruit were harvested at commercial maturity as follows: 40 Honeycrisp fruit per tree on 5 Sep, 75 Royal Court fruit per tree on 18 Sep, and 40 Cameo fruit per tree on 29 Oct. Accumulated rainfall between the last spray on 14 Aug and harvest dates for therespective cultivars totaled 1.0, 3.0 and 7.5 in. The accumulated hours of leaf wetting for those same preharvest intervals were 97, 184, and 454, respectively. Both the Honeycrisp and Royal Court fruit were rated for sooty blotch, flyspeck, and summerfruit rots or lenticel spots immediately after harvest. Fruit with rots or lenticel spots were discarded. Twenty-five Honeycrisp and 50 Royal Court fruit from each tree were then wounded and incubated to allow infection by surviving wound-decay pathogenspresent on the fruit surface at harvest and development of flyspeck and sooty blotch infections that were not yet visible. Fruit were wounded on a single face using a cork with three nails three-eighth in. apart in a triangular pattern that created wounds approximately one-eighth in. deep by one-sixteenth in. diameter. The wounded fruit were placed into plastic crates, water-soaked paper towels were added, the crates were enclosed in polyethylene bags, and fruit were incubated at 100% relative humidityand 70 °F for 14 (Royal Court) or 18 (Honeycrisp) days to allow development of incubating infections on the fruit surface and/or of wound decays from naturally occurring inoculum present on fruit surfaces. At the end of the incubation period, disease incidence was evaluated again. Cameo fruit were harvested several weeks later than normal commercial harvest dates and were not incubated after harvest.