After-infection control of quince rust on Red Delicious and Golden Delicious apples, 2014

摘要

Quince rust overwinters in perennial cankers on Eastern Red Cedar and can produce an abundance of inoculum each year, but quince rust has a rather narrow infection window —just from about pink stage until shortly after petal fall. Because of this narrow infection window and the need for infection periods >55°F, quince rust occurs only sporadically, with serious outbreaks in 2000, 2003, 2008 and 2014. Most of the infection in 2014 occurred during a 67-hour wetting period with a total of 1.8 in. of rain near mid-bloom, 28 April-1 May. Two apple blocks had not received any fungicides prior to this extended wetting period and treatments were applied in the following week or two. These were the only fungicides applied through the test period. The primary objective was to test half rates of SI fungicides, but also to test the combination of Regalia + JMS Stylet-Oil which has shown promise for cedar-apple rust control for organic production. Dilute rates were based on 400 gal/A. Both test blocks were set up with four randomized blocks. In Golden Delicious, treatments were applied dilute to runoff 2 May (#1-5) or 5 May (#6-8), approximately three and six days post-infection. Treatments were applied to Red Delicious 16 May, approximately 17 days post-infection. Quince rust infection was rated on 100 Golden Delicious fruit per tree 3 Jun and on 50 Red Delicious fruit per tree 3 Jul.