EVALUATION OF PECAN SCAB DISEASE MANAGEMENT STRATEGIES TO IMPROVE ORCHARD PRODUCTION AND REDUCE PESTICIDE INPUTS By ANDREA F. PAYNE Bachelor of Science in Microbiology Oklahoma State University Stillwater, OK 2007 Master of Public Health in Epidemiology Tulane University New Orleans, LA 2009 Submitted to the Faculty of the Graduate College of the Oklahoma State University in partial fulfillment of the requirements for the Degree of MASTER OF SCIENCE May, 2011 EVALUATION OF PECAN SCAB DISEASE MANAGEMENT STRATEGIES TO IMPROVE ORCHARD PRODUCTION AND REDUCE PESTICIDE INPUTS Thesis Approved: Dr. Damon L. Smith Thesis Adviser Dr. John Damicone Dr. Michael Smith Dr. Mark E. Payton Dean of the Graduate College ii ACKNOWLEDGMENTS I would like to thank my advisor Dr. Damon L. Smith for not only accepting me as his first graduate student, but also being such a strong leader and role model over these past 2 years. He took a large leap of faith accepting a student from the medical field who had no background in horticulture and limited experience in agriculture and has turned her into a plant pathologist. For that faith and patience I will also be indebted. I would also like to thank the remaining members of my committee, Dr. John Damicone and Dr. Michael Smith. Their guidance has been incredibly helpful throughout my studies. With so many different ways of designing studies and analyzing their results having such a diverse committee was my greatest asset. A special thanks to the Oklahoma Pecan Growers Association for partially funding this project and allowing me the opportunity to speak at their annual meetings and gain those experiences. Finally, I would like to thank my family for all their support and words of encouragement during my graduate studies. It’s been a long and arduous road that will continue, but with my family and friends behind me I know I’ll make it. iii TABLE OF CONTENTS Chapter Page I. REVIEW OF LITERATURE .....................................................................................1 Definition of Epidemiology .....................................................................................1 Background and Breeding of the Pecan Tree ..........................................................3 Nutritional Requirements of the Pecan Tree ............................................................5 Common Diseases and Insect Pests of Pecan Trees ................................................6 Taxonomy of Fusicladium effusum .........................................................................7 Occurrence of Pecan Scab .......................................................................................9 Pecan Scab Disease Cycle .......................................................................................9 Factors affecting Conidial Dispersal ......................................................................12 Isolate variability within F. effusum populations ...................................................13 Timing of Fungicide Applications to Manage Pecan Scab ....................................13 Fungicide use in Pecan Production ........................................................................17 Statistical Techniques Logistic Regression ..........................................................................................19 Generalized Estimating Equations ...................................................................21 Literature Cited ......................................................................................................24 II. INDUCING SPORULATION BY THE FUNGUS FUSICLADIUM EFFUSUM IN VITRO ....................................................................................................................31 Abstract ..................................................................................................................31 Introduction ............................................................................................................32 Materials and Methods ...........................................................................................33 Results ....................................................................................................................35 Discussion ..............................................................................................................36 Literature Cited ......................................................................................................39 III. DEVELOPMENT AND EVALUATION OF PECAN SCAB PREDICTION MODELS USING REPEATED MEASURES LOGISTIC REGRESSION ANALYSIS ............................................................................................................46 Abstract ..................................................................................................................46 Introduction ............................................................................................................47 Materials and Methods ...........................................................................................52 Results ....................................................................................................................57 iv Chapter Page Discussion ..............................................................................................................60 Literature Cited ......................................................................................................66 IV. FIELD EVALUATION OF ABBREVIATED FUNGICIDE PROGRAMS FOR CONTROL OF PECAN SCAB………………………………………………………80 Abstract ..................................................................................................................80 Introduction ............................................................................................................81 Material and Methods ............................................................................................84 Results ....................................................................................................................85 Discussion ..............................................................................................................87 Literature Cited ......................................................................................................89 APPENDICES .............................................................................................................97 v LIST OF TABLES Table Page 1 Composition of media used in this study ................................................................41 2 Analysis of variance (ANOVA) of main and interactive effects of media and isolate on percent sporulating area. ....................................................................................42 3 Analysis of variance (ANOVA) of main and interactive effects of media and isolate on estimation of total spore production. .................................................................43 4 Effects of weather-based advisory programs on levels of pecan scab during 2009 and 2010 growing seasons in Madill, OK .....................................................................71 5 Single-effects models describing the probability of a scab event greater than 25% fruit severity using either dew point (DP), air temperature (T), relative humidity (RH), total solar radiation (SR), rain events (R where 1=rain event ≥ 2.5mm; 0=0 to < 2.5mm), and total rainfall (TR) as independent variables ......................................72 6 Evaluation of models predicting the probability of a scab event greater than 25% fruit severity using air temperature (T), relative humidity (RH), total solar radiation (SR), rain events (R where 1=rain ≥ 2.5mm; 0= < 2.5 mm), and total rainfall (TR) as independent variables ..............................................................................................73 7 Best fitting multivariable models describing the probability of a scab event using, dew point depression (DPD), dew point (DP), binomial output of rain events (R where 1=rain event ≥ 2.5mm and 0 < 2.5 mm), rain accumulation (TR), and total solar radiaiton (SR) as independent variables .........................................................74 8 Monthly accumulated scab hours for Perkins, Oklahoma during the 2009 and 2010 growing seasons .....................................................................................................92 9 Effects of fungicide programs on levels of pecan scab during 2009 and 2010 growing seasons in Perkins, OK ...........................................................................................93 vi LIST OF FIGURES Figure Page 1 A sigmoidal curve demonstrating the probability of an event (response) on the y- axis in response to the independent parameter (Dose) on the x-axis. .................30 2 Means of percent sporulating area of isolates on Potato Dextrose Agar, Potato Carrot Agar amended with 50% Lactic Acid, Malt Extract Agar, and Sabouraud Dextrose Agar. ....................................................................................................44 3 Main effects of media and isolates on spore production. ....................................45 4 Pecan yield during the 2009 and 2010 growing seasons for plots sprayed with fungicide according to the Oklahoma Agweather Pecan Scab Fungicide Advisory - using five combinations of air temperature and relative humidity thresholds to calculate ‘scab hours.’ .........................................................................................75 5 Evaluation of best fitting T/RH based