1. Effect of defoliation on growth and fruit production of Brazilian pepper tree, Schinus terebinthifolius Raddi (Anacardiaceae) Lucinda W. Treadwell and James P. Cuda University of Florida Heteroperryia hubrichi: 1 major, 1 minor population peak/year in native Brazil often attack the same small tree year after year An attractive but highly aggressive and competitive ornamental that has invaded all of South Florida OBJECTIVES To simulate defoliation of Brazilian pepper tree (BP) by specialist larvae of the sawfly Heteroperreyia hubrichi (Hymenoptera: Pergidae), a candidate for classical biological control of BP To measure the effect of that defoliation on growth and reproductive output of BP, in terms of: height and canopy diameter seed output: dry weight and numbers METHODS and MATERIALS One row of 12 small trees, 8 m apart, along each of 3 irrigation canals at Indian River Research and Education Center, Fort Pierce, in early June 2001 Treatments randomly assigned among each subblock of 6 trees to minimize effects of site variability: 3 100% defoliation incidents (0, 1, or 2) per year Defoliation in 1 year only, with monitoring for long-term effects, or over the course of 2 years Heights and N-S and E-W canopy diameters measured every 4 weeks Fruit from all branches of all female plants harvested in November 2002, counted, dried, and weighed Height and diameter data analyzed by SAS PROC MIXED Fruit data analyzed by SAS PROC GLM, LSMeans comparison Experimental Design: trtnno. def/yrno. yrs defoliation dates a control1200 ---- 11611 Fall 01 12612 Fall 01, Fall 02 21621 Fall 01, Spring 02 23623 Fall 01, Spring 02, Fall 02, Spring 03, Fall 03 a specific dates of defoliations: Fall 01 = 8/27/01, Spring 02 = 5/11/02, Fall 02 = 9/27/02, Spring 03 = 4/26/03, Fall 03 = 9/22/03 RESULTS and CONCLUSIONS Multiple defoliations significantly reduced height and canopy growth throughout the 2 years; trees in this treatment actually lost height because top growth died back Trees defoliated 2 times in 1 year or 1 time in each of 2 years trended smaller than controls; 2 defoliations also trended toward decreased fruit production in comparison to controls in the first year Trees defoliated only 1 time, in the fall, had significantly wider canopies than controls and were significantly taller than the other defoliation treatments, 2 years later A single defoliation also produced significantly more fruit, in terms of numbers as well as dry mass, than the controls and the other defoliation treatments in the first year Fruit data were extremely variable in both years, with standard errors (not shown) approximately equal to or greater than means; analysis for significant differences is not yet completed. ACKNOWLEDGMENTS We are grateful for the field assistance of Bancroft Whitely. This research was funded by grants from South Florida Water Management District, Florida Department of Environmental Protection, and Florida Exotic Pest Plant Council. Background: Brazilian pepper as far as the eye can see, in the Florida Everglades. Photo courtesy D. Schmitz, FDEP Heights of Brazilian pepper trees subjected to 100% defoliation 1 or 2 times/year for 1 or 2 years Canopy diameters of Brazilian pepper trees subjected to 100% defoliation 1 or 2 times/year for 1 or 2 years a ab a b c abbbcabbbcb sequences with different letters are statistically different at α =.05 (SAS PROC MIXED) Fruit output of Brazilian pepper trees subjected to 100% defoliation 1 or 2 times/year for 1 or 2 years 20032004 1 defoliation 4 defoliations