Evaluating the Current Weed Community in Wild Blueberry Fields and IPM Strategies for Spreading Dogbane (Apocynum Androsaemifolium)
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The University of Maine DigitalCommons@UMaine Electronic Theses and Dissertations Fogler Library Winter 12-18-2020 Evaluating the Current Weed Community in Wild Blueberry Fields and IPM Strategies for Spreading Dogbane (Apocynum androsaemifolium) Anthony G. Ayers University of Maine, [email protected] Follow this and additional works at: https://digitalcommons.library.umaine.edu/etd Part of the Agricultural Science Commons, Agronomy and Crop Sciences Commons, Botany Commons, Horticulture Commons, Plant Pathology Commons, and the Weed Science Commons Recommended Citation Ayers, Anthony G., "Evaluating the Current Weed Community in Wild Blueberry Fields and IPM Strategies for Spreading Dogbane (Apocynum androsaemifolium)" (2020). Electronic Theses and Dissertations. 3321. https://digitalcommons.library.umaine.edu/etd/3321 This Open-Access Thesis is brought to you for free and open access by DigitalCommons@UMaine. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of DigitalCommons@UMaine. For more information, please contact [email protected]. EVALUATING THE CURRENT WEED COMMUNITY IN WILD BLUEBERRY FIELDS AND IPM STRATEGIES FOR SPREADING DOGBANE (Apocynum androsaemifolium) By Anthony Ayers B.A. SUNY College of Environmental Science and Forestry, 2012 A THESIS Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science (in Plant, Soil and Environmental Sciences) The Graduate School The University of Maine December 2020 Advisory Committee: Lily Calderwood, Extension Wild Blueberry Specialist and Assistant Professor of Horticulture, Advisor Eric Gallandt, Professor of Weed Ecology Seanna Annis, Associate Professor of Mycology EVALUATING THE CURRENT WEED COMMUNITY IN WILD BLUEBERRY FIELDS AND IPM STRATEGIES FOR SPREADING DOGBANE (Apocynum androsaemifolium) By Anthony Ayers Thesis Advisor: Dr. Lily Calderwood An Abstract of the Thesis Presented in Partial Fulfillment of the Requirements for the Degree of Master of Science (in Plant, Soil and Environmental Sciences) December 2020 Lowbush blueberry (Vaccinium angustifolium) is Maine’s third largest-yielding crop (USDA 2020 a). From 2017 – 2019 the three season average yield was 57 million pounds which was harvested from 19,500 acres for a value of $22,468,000 (USDA 2020 c). A common challenge for farmers is the presence of weeds within their fields. Weeds take up valuable water, shade, nutrients and space that would otherwise be utilized by the lowbush blueberry. Weeds can reduce yield, increase disease incidence and interfere with harvest operations. Up to 84% of yield can be lost because of weed cover (Yarborough 2009; Yarborough and Mara 1997). There has not been a weed survey of lowbush blueberry fields in the state of Maine since 1980 (Yarborough and Bhowmik, 1989). We surveyed twenty fields in the field seasons of 2019-2020. Survey methods were similar to McCully et al. (1991) and used the Daubenmire Cover Rating System to measure surface area (Daubenmire 1959). Additionally, we interviewed farmers to learn how they have been managing weeds and to learn how they perceive their weeds. We ranked weeds by their frequency and surface area for both organic and conventional fields, allowing us to compare notable weeds and trends between the two systems. Our survey found more species and genera of weeds present in fields than Yarborough and Bhowmik (1989). Interview results showed that most farmers were able to correctly estimate the severity of weed coverage in their fields. The most frequent method of weed control was mowing, followed by string trimmer mowing. One of the most difficult weeds to manage within wild blueberry fields is spreading dogbane (Apocynum androsaemifolium). It resists at least six common herbicides (NBDAAF 2017) and can form dense patches through its rhizomes (Niering et al. 2001). Yarborough and Marra (1997) found that if left untreated, spreading dogbane patches reduced yield by 74%. Because of its resilient nature and negative effects on yield, research on spreading dogbane management is a priority. One facet of weed management is the use of biocontrol. While weeds in other agricultural systems have been managed through the use of pathogenic fungi, no research has been published on the use of fungi to manage spreading dogbane. The periodic mowing of woody weeds throughout the growing season has been found to significantly reduce patches of willow (Salix spp.) and white birch (Betula papyrifera Marshall). We considered if the same cutting strategy could show similar success on dogbane patches. In the summer of 2019, dogbane leaves with leaf spots were collected, and the fungi on these leaf spots were grown on potato dextrose agar. Spores were identified to genus using Malloch (1981). To measure the effectiveness of string trimmer mowing, sixteen patches of dogbane were mowed at different frequencies. Stem height, patch area, and number of stems per patches were collected before each cutting event. Two genera of fungi were found from the leaf spots: Ulocladium and Alternaria. Mowed patches of dogbane grew wider and had more stems than those that were not mowed. DEDICATION I’d like to dedicate this thesis to everyone that believed in me. My parents, my friends, and my mentors. Your support means the world to me. i ACKNOWLEDGEMENTS I’d like to thank the following for helping me directly with this thesis: Dr. Lily Calderwood, Dr. Seanna Annis, Dr. Eric Gallandt, Brogan Tooley, Mary Michaud, Becky Gumbrewicz, Bill Halteman, Greg Kornelis, Will Peterson, Dr. Henri Vanhanen, Louis Morin, Dr. Robert Causey, Dr. Bryan Peterson, Sydney Abramovich and Aidan Lurgio. Thank you to the following funders for contributing to my research assistantship and research activities: National Institute of Food and Agriculture (NIFA MAFES), University of Maine School of Food and Agriculture, University of Maine Cooperative Extension, and the Maine Food and Agriculture Center. ii TABLE OF CONTENTS DEDICATION .................................................................................................................................................................... i ACKNOWLEDGEMENTS .................................................................................................................................................. ii LIST OF TABLES .............................................................................................................................................................. v LIST OF FIGURES .......................................................................................................................................................... vii LIST OF EQUATIONS ...................................................................................................................................................... ix 1 EVALUATING THE CURRENT WEED COMMUNITY IN LOWBUSH BLUEBERRY FIELDS .............................................. 1 1.1 Abstract ........................................................................................................................................................... 1 1.2 Introduction .................................................................................................................................................... 1 1.2.1 Lowbush Blueberry Background ..................................................................................................... 1 1.2.2 Weeds and Weed Surveys in Lowbush Blueberry Fields ................................................................. 2 1.3 Materials and Methods.................................................................................................................................. 4 1.3.1 Weed Survey ................................................................................................................................... 4 1.3.2 Data Analysis ................................................................................................................................... 6 1.3.3 Farmer Interviews ........................................................................................................................... 7 1.4 Results .......................................................................................................................................................... 8 1.4.1 Weed Survey Results ....................................................................................................................... 8 1.4.2 Farmer Interview Results .............................................................................................................. 16 1.5 Discussion ................................................................................................................................................... 18 1.5.1 Weed Survey Discussion................................................................................................................ 18 1.5.2 Farmer Interview Discussion ......................................................................................................... 19 1.6 Conclusions ................................................................................................................................................. 20 2 EXPLORING IPM TOOLS FOR SPREADING DOGBANE (Apocynum androsaemifolium) MANAGEMENT IN LOWBUSH BLUEBERRY FIELDS .................................................................................................. 21 2.1 Abstract........................................................................................................................................................