Poster: Biology & Disease Mgmt: Chemical Control
Contribution of protectant fungicides applied as mid-season cover sprays to management of peach brown rot at harvest
N. LALANCETTE (1), N. Lalancette (1), L. Blaus (1), J. Gager (1), K. McFarland (2) (1) Rutgers University, Agricultural Research & Extension Center, U.S.A.; (2) Rutgers University, Agricultural Research & Extension Center, U.S.A.
Protectant fungicides are routinely applied to peach trees during the period from shuck-split through early preharvest. These cover sprays are usually applied to control peach scab, rusty spot, and anthracnose. However, results from fungicide treatments in 2010, which lacked the typical preharvest applications, indicated that these mid-season sprays may also provide control of brown rot at harvest, caused by Monilinia fructicola. To confirm these observations and determine the mechanism of control, a field study was conducted from 2012-2015 in an experimental peach orchard. In each year, four protectant fungicides (captan, sulfur, ziram, and thiram) were applied from shuck-split through sixth cover. Captan and thiram in 2012 and captan in 2013 and 2015 significantly reduced brown rot at harvest. Estimation of fungicide levels on fruit in 2013 to 2015, using an in vivo bioassay based on M. fructicola spore germination, showed that residual activity was the primary mechanism for control. Results also showed that captan may have a higher intrinsic efficacy than the other protectants, thereby allowing extended control through the preharvest period. These findings indicate that residual activity from mid-season applications of protectant fungicides (i) can contribute significantly to the efficacy of preharvest programs and (ii) may play an important role in reducing selection for resistance among site-specific fungicides typically applied during the preharvest period.