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Peach tree fungal gummosis caused by Botryosphaeria dothidea [(Moug.:Fr.) Cos & de Not.] is widespread throughout the southeastern United States. Until recently, its economic impact on peach [Prunus persica (L.) Batsch] has been impossible to estimate, since no effective controls were known. Significant, though not total, suppression of gummosis on `Summergold' peach trees was achieved with an intensive 5-year spray program with captafol. Captan was far less effective than captafol. Both trunk diameter and fruit yield were negatively correlated with disease severity. After eight growing seasons, trees treated with captafol were 18% larger than the untreated trees. Yield of mature captafol-treated trees was 40% to 60% high er than that of untreated ones. Following termination of the spray program after 5 years, disease severity gradually increased on both captafol- and captan-treated trees. However, through eight growing seasons, disease severity was significantly lower on captafol-treated trees. This study demonstrates that peach tree fungal gummosis significantly depresses tree growth and fruit yield on susceptible peach cultivars.
Five years of testing found equal damage on peaches from trees sprayed with an air-blast sprayer or with a PASS. A PASS is a modified boom sprayer mounted on the lower truss of a center-pivot. A PASS and an air-blast sprayer apply the same chemical formulations at the same rates per ha. Because a PASS injects no chemicals into the center-pivot, it is not chemigation. Unlike an air-blast sprayer that sprays out and up, a PASS sprays down, which should result in less spray drift. Because a PASS sprays over the tops of the trees, it places no restriction on row or tree spacing. Also, a PASS eliminates the pesticide exposure of a tractor driver spraying with an air-blast sprayer. Comparing capital costs of a PASS and an air-blast sprayer showed projected savings for the PASS of from $128/ha to over $248/ha as the orchard size increased from 7 ha to 29 ha. A PASS is much simpler than an air-blast sprayer which is pulled by a tractor, so the operating and maintenance costs for a PASS should be lower.