Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2019 Disease and insect pest management in organic cucurbit production Hayley Nelson Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Agriculture Commons, and the Plant Pathology Commons Recommended Citation Nelson, Hayley, "Disease and insect pest management in organic cucurbit production" (2019). Graduate Theses and Dissertations. 17066. https://lib.dr.iastate.edu/etd/17066 This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Disease and insect pest management in organic cucurbit production by Hayley Marie Nelson A thesis submitted to the graduate faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Major: Plant Pathology Program of Study Committee: Mark L. Gleason, Major Professor Gwyn A. Beattie Erin W. Hodgson Ajay Nair Alison E. Robertson The student author, whose presentation of the scholarship herein was approved by the program of study committee, is solely responsible for the content of this thesis. The Graduate College will ensure this thesis is globally accessible and will not permit alterations after a degree is conferred. Iowa State University Ames, Iowa 2019 Copyright © Hayley Nelson, 2019. All rights reserved. ii TABLE OF CONTENTS ABSTRACT ........................................................................................................................................ iv CHAPTER 1. GENERAL INTRODUCTION ........................................................................................... 1 Thesis Organization ..................................................................................................................... 1 Literature Review ........................................................................................................................ 1 Cucurbits ................................................................................................................................. 1 Organic cucurbits .................................................................................................................... 2 Major pest and disease complexes of cucurbit crops in the Upper Midwest ........................ 3 Bacterial wilt and cucumber beetles ...................................................................................... 3 Squash bug and CYVD ............................................................................................................. 5 Squash vine borer ................................................................................................................... 6 Organic pest management...................................................................................................... 6 Organic weed management and soil health ......................................................................... 12 Case-based teaching ............................................................................................................. 13 Thesis Objectives....................................................................................................................... 15 Literature Cited ......................................................................................................................... 15 CHAPTER 2. COMPARISON OF ROW COVER SYSTEMS FOR PEST MANAGEMENT IN ORGANIC MUSKMELON AND ACORN SQUASH ............................................................................................. 21 Abstract ..................................................................................................................................... 21 Introduction .............................................................................................................................. 22 Materials and Methods ............................................................................................................. 25 Results ....................................................................................................................................... 31 Discussion.................................................................................................................................. 34 Conclusion ................................................................................................................................. 37 Acknowledgements ................................................................................................................... 37 Literature Cited ......................................................................................................................... 38 Tables ........................................................................................................................................ 41 Figures ....................................................................................................................................... 45 iii CHAPTER 3. COMPARISON OF MULCHES FOR WEED MANAGEMENT IN MESOTUNNELS IN ORGANIC MUSKMELON AND ACORN SQUASH ............................................................................ 47 Abstract ..................................................................................................................................... 47 Introduction .............................................................................................................................. 48 Materials and Methods ............................................................................................................. 50 Results ....................................................................................................................................... 55 Discussion.................................................................................................................................. 57 Conclusion ................................................................................................................................. 58 Acknowledgements ................................................................................................................... 59 Literature Cited ......................................................................................................................... 59 Tables ........................................................................................................................................ 62 CHAPTER 4. SOLVING A DISEASE MANAGEMENT PUZZLE IN ORGANIC MUSKMELON ................ 65 The Case .................................................................................................................................... 65 Discussion Questions ................................................................................................................ 70 Disease Management ............................................................................................................... 71 Discussion Questions ................................................................................................................ 75 Background ............................................................................................................................... 76 Instructor Resources ................................................................................................................. 84 CHAPTER 5. GENERAL CONCLUSIONS ........................................................................................... 87 APPENDIX. ADDITIONAL DATA ...................................................................................................... 90 iv ABSTRACT Organic production of cucurbit crops in the Midwest is limited by several insect pests (e.g., striped cucumber beetle, spotted cucumber beetle, squash bug, squash vine borer) and the bacterial diseases they vector (e.g., cucurbit bacterial wilt and cucurbit yellow vine disease (CYVD)). Current management strategies – low tunnels and insecticides – fail to provide reliable protection, are not durable, and are harmful to beneficial insects such as pollinators. Organic producers in the Midwest need more effective pest management options to consistently produce cucurbit crops. A 3-year field experiment aimed to develop new row cover strategies for full-season, organic control of cucurbit insect and disease pests. The objectives were to evaluate traditional and modified row cover strategies for differences in incidence of disease and insect pest damage, number of insecticide applications, number and weight of marketable fruit, and maximum temperatures inside tunnels. Full-season “mesotunnels” – nylon-mesh fabric supported by 3.5-foot-high conduit hoops - resulted in the lowest incidence of disease and insect pest damage in muskmelon and acorn squash, and no disease or insect pest damage in muskmelon. Full-season mesotunnels required no insecticide applications, whereas a noncovered control treatment required the most insecticide applications and part-season mesotunnels and low tunnels were intermediate. The weight of marketable muskmelon in full- season mesotunnels was higher than in the noncovered control for all 3 years and higher than in the low tunnels and part-season mesotunnels for 1 of 3 years. The weight of marketable muskmelon