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ISHS Acta Horticulturae 1137: International Symposium on Innovation in Integrated and Organic Horticulture (INNOHORT)

Non-target impacts of agricultural biostimulants compared with sulfur-based fungicides on pest and beneficial arthropods on three cultivars in a certified organic apple orchard in Vermont, ME, USA

Authors:   A.L. Hazelrigg, L.P. Berkett, H.M. Darby, J.H. Görres, R.L. Parsons
Keywords:   integrated pest management, 'Ginger Gold', 'Honeycrisp', 'Liberty', European red mite, two-spotted spider mite
DOI:   10.17660/ActaHortic.2016.1137.23
Growers and researchers are searching for suitable alternatives to sulfur-based fungicides for disease control in organic apple orchards. Agricultural biostimulants, used alone or in combination with fungicides, may offer new, low environmental-impact options for disease management. The objective of this two-year study was to evaluate the non-target or unintended effects of an organic disease management system containing agricultural biostimulants compared to two sulfur-based systems on pest and beneficial arthropod populations on three cultivars in a certified organic orchard. This research was part of a comprehensive project; the impacts of the systems on diseases, tree growth, and fruit yield and quality have been previously reported elsewhere in this publication. All research was performed on the same trees, using the same experimental design and three disease organic management systems. The use of the agricultural biostimulants had very limited non-target effects; when present, they were beneficial in suppressing insect pest incidence and/or damage on foliage, compared to one or both of the sulfur-based fungicide systems. However, many insect pests or their damage were not observed on the foliage or had an incidence of less than 1% in any of the systems. The biostimulant system suppressed European red mites (Panonychus ulmi) in both years compared to both sulfur-based systems when data were averaged across cultivars. On fruit, no differences in non-target impacts from the major insect pests were observed among any of the three systems except for surface-feeding Lepidoptera damage. In summary, the organic disease management system containing biostimulants did not have different non-target impacts for almost all of the pest and beneficial arthropods evaluated in this study (vs. sulfur-based systems). Before this novel disease management approach in commercial orchards is adopted, the effects of the biostimulants on important diseases, in addition to the effects on tree growth, yield and fruit quality must be considered.

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