AMERICAN BLACK NIGHTSHADE (Solanum americanum MILL.) INTERFERENCE IN WATERMELON (Citrullus lanatus L.) By CELESTE ALINA GILBERT A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2006 Copyright 2006 by Celeste Alina Gilbert This thesis is dedicated to my grandmother, Claire K. Gilbert, who inspired me to pursue a degree in science through her love and support. ACKNOWLEDGMENTS First and foremost I wish to thank my advisor, Dr. William M. Stall, for all the help and guidance he has given me throughout my time at the university and especially throughout the writing process. Without his patience and guidance I would not have been able to write this thesis. I would also like to thank my committee members for their assistance and support throughout my program. I am extremely grateful to Dr. Eric Simonne, whom I consider a mentor and a friend throughout my time in Gainesville. For their assistance in the field and with my research I would like to thank the farm crews at the NFREC and PSREU, especially Berry Tanner and Darrel Thomas, for their friendships and support. I would also like to thank Aparna Gazula for both her help with statistics and her wonderful friendship, without which I would have struggled. For all their wonderful support and kindness I wish to thank all my friends here in Florida; they have provided me with support and generosity throughout my time in Gainesville. Finally, I wish to thank my parents, Donna and John Gilbert, for their interest and underlying support for my research, my brother and sister Chaz and Carolina Gilbert for their encouragement and love, and my grandmother Claire Gilbert, whose faith in me has given me strength through the tougher times. iv TABLE OF CONTENTS page ACKNOWLEDGMENTS .......................................................................................iv LIST OF TABLES ............................................................................................... viii LIST OF FIGURES ...............................................................................................ix ABSTRACT ..........................................................................................................xi CHAPTER 1 LITERATURE REVIEW.................................................................................. 1 Competition.................................................................................................... 1 Economic Impact ..................................................................................... 2 Designs for Studying Competition in Agriculture...................................... 3 Additive studies ................................................................................. 3 Substitutive studies (replacement series).......................................... 4 Systematic studies ............................................................................ 4 Neighborhood (area of influence) studies.......................................... 5 Review of American Black Nightshade and the Nightshade Complex ........... 5 Origins and Distribution of American Black Nightshade (S. americanum) .................................................................................. 6 History ..................................................................................................... 6 Vegetative Characteristics of Solanum Americanum............................... 7 Black Nightshade Biology ........................................................................ 7 Germination of Black Nightshade Seed................................................... 8 Temperature...................................................................................... 8 Other treatments to promote germination.......................................... 9 Osmotic pressure and pH................................................................ 10 Critical Weed-Free Periods and Densities for Nightshade..................... 11 Control of Black Nightshade......................................................................... 12 Mechanical Control................................................................................ 12 Cultural Control...................................................................................... 12 Chemical Control ................................................................................... 14 Biological Control................................................................................... 14 Review of Watermelon (Citrullus lanatus) .................................................... 14 Watermelon Taxonomical Description ................................................... 14 Watermelon Production in Florida.......................................................... 16 v Weed Studies in Watermelon ................................................................ 17 Watermelon Nutritional and Cultural Requirements ..................................... 18 Nutrition ................................................................................................. 18 pH.......................................................................................................... 19 Temperature .......................................................................................... 20 Mulches and Growth: High and Low Maintenance ................................ 21 Mulches........................................................................................... 21 Plant spacing................................................................................... 22 Water and nutrients......................................................................... 23 Transplants versus seeded ............................................................. 23 2 SEASON-LONG INTERFERENCE BETWEEN WATERMELON AND AMERICAN BLACK NIGHTSHADE ............................................................. 25 Introduction .................................................................................................. 25 Objectives .................................................................................................... 25 Materials and Methods................................................................................. 26 Measurable Variables ............................................................................ 27 Experimental Design and Statistical Analysis ........................................ 28 Results ......................................................................................................... 29 2005....................................................................................................... 29 2006....................................................................................................... 30 Nightshade Dry Weight.......................................................................... 31 PAR. ...................................................................................................... 31 Plant Measurements.............................................................................. 32 Discussion.................................................................................................... 32 3 SPATIAL DISTANCE STUDY BETWEEN AMERICAN BLACK NIGHTSHADE (Solanum americanum Mill.) AND WATERMELON (Citrullus lanatus L.) ..................................................................................... 46 Objective ...................................................................................................... 46 Materials and Methods .......................................................................... 46 Measurable Variables ............................................................................ 47 Experimental Design and Statistical Analysis ........................................ 48 Results and Discussion................................................................................ 48 4 SEED GERMINATION TRIALS USING AMERICAN BLACK NIGHTSHADE SEED................................................................................... 51 Objectives .................................................................................................... 51 Material and Methods................................................................................... 51 Bleach treatment ............................................................................. 52 Pre-germination treatment............................................................... 52 Germination trials ............................................................................ 52 Statistical Analysis................................................................................. 53 Results ......................................................................................................... 53 vi Trial 1: September 8-22, 2005 ............................................................... 54 Trial 2: November 3-17, 2005 ................................................................ 54 Trial 3: January 29- Febuary 12, 2006................................................... 55 Discussion.................................................................................................... 55 5 SUMMARY AND CONCLUSIONS ............................................................... 59 APPENDIX ENVIRONMENTAL CONDITIONS FOR EACH YEAR AND SITE...................... 62 REFERENCES................................................................................................... 63 BIOGRAPHICAL SKETCH ................................................................................