Control of peach scab with reduced midseason fungicide programs

The effectiveness of reduced fungicide programs, using either extended appl ication intervals or alternate-row middle (ARM) spraying of wettable sulfur or captan, on infection of peach fruit by Cladosporium carpophilum was inv estigated in a 2-year study in Georgia. Fungicide reductions focused on the midseason cover spray period when scab pressure is typically reduced and w hen growers would be most likely to adopt reduced spray programs because of the potential for fewer insecticide applications at the same time. In an e xperimental orchard, sulfur was applied at calyx split and calyx fall, foll owed by another application of sulfur or captan at first cover. Subsequent midseason applications consisted of sulfur at 12- to 14-day intervals (stan dard); sulfur at extended 24- to 28-day intervals; or either sulfur or capt an applied via ARM spraying at 12- to 14-day intervals at reduced sprayer s peed. Plots without midseason sprays after first cover also were included. Fruit scab severity was reduced by all fungicide programs compared with the untreated control. Disease severity with sulfur applied at extended interv als and with ARM spraying of sulfur or captan was not significantly differe nt from that of the standard (P > 0.05) in both years, suggesting that appl ication intensity during midseason can be reduced without compromising scab control. By contrast, plots that did not receive any midseason sprays afte r first cover had significantly more disease. Reduced midseason application s of sulfur were further evaluated in two commercial orchards. In one orcha rd, fruit scab control achieved with extended-interval or ARM spraying duri ng midseason was not significantly different from that of the grower standa rd. In the second orchard, higher disease severity resulted from midseason ARM applications compared with the standard, presumably because of the long er (14- to 18-day) spray interval used by the cooperating grower for ARM sp raying. Reduced midseason fungicide programs did not lead to an increased c arryover of inoculum as determined by conidial counts on overwintered twigs at petal fall in the following year.