APS Abstract of Presentation

Combining sanitation practices with timing of scab sprays in organic apple production
I. J. HOLB (1)
(1) University of Debrecen, Centre of Agricultural Sciences, P.O. Box 36, H-4015 Debrecen, Hungary
Phytopathology 98:S68

The aim of this study was to evaluate scab control efficacy in integrated approaches of i) three sanitation treatments (fallen leaf removal combined with winter pruning and non-sanitized control), ii) three onsets of first fungicide sprays (dormant bud, early tight cluster and pink bud stage), and iii) three final dates for finishing fungicide programs (mid-July, mid-August and mid-September) in an organic apple orchard on two cultivars. Results on scab resistant cultivar Prima indicated that sprays against scab could be omitted before pink bud stage and after mid-July by holding the threshold of 1% fruit scab incidence. On moderately scab susceptible cultivar Jonathan, a delay in the onset of first spray until pink bud stage resulted in higher scab incidences on both leaves (16.6–20.6%) and fruits (13.1–15.3%) compared with the non-delayed spray treatments (5.2–8.3% and 6.7–9.4%, respectively). Final leaf and fruit scab incidence increased significantly when sprays were omitted after mid-July compared to spray treatments finished at mid-August or mid-September. A combination of leaf removal with pruning resulted in lower scab incidence (5.2–11.8%) compared with the non-sanitized plots (6.7–14.7%) when spray treatments were finished at mid-August or mid-September. Results on cultivar Jonathan suggested that sprays against scab could only be omitted before early tight cluster stage and after mid-August if leaf removal combined with pruning was applied.