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8/01 10/01 12/01 2/02 4/02 6/02 8/02 9/02 11/02 1/03 4/03 5/03 7/03 9/03 11/03

mea

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)

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11: def Fall 01

12: def Fall 01, Fall 02

21: def Fall 01, Spring 02

22: def Fall 01, Spring 02, Fall 02, Spring 03

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0: control

11: def Fall 01

12: def Fall 01, Fall 02

21: def Fall 01, Spring 02

22: def Fall 01, Spring 02, Fall 02, Spring 03

Effect of defoliationEffect of defoliation on growth and fruit production on growth and fruit production of Brazilian pepper tree, of Brazilian pepper tree, Schinus terebinthifoliusSchinus terebinthifolius

Raddi (Anacardiaceae)Raddi (Anacardiaceae)

Lucinda W. Treadwell and James P. CudaUniversity 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:

trt n no. def/yr no. yrs defoliation datesa

control 12 0 0 ----

11 6 1 1 Fall 01

12 6 1 2 Fall 01, Fall 02

21 6 2 1 Fall 01, Spring 02

23 6 2 3 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

aab

a

b

c

a

b

b

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c

sequences with different letters are statistically different at α = .05 (SAS PROC MIXED)

1

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control 11 12 21 22

treatment groups

num

ber

s of

fruit

,fr

uit

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(gm

) (l

og s

cale

)

no. of fruits

fruit dry weight

1

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control 11 12 21 22

treatment groups

Fruit output of Brazilian pepper trees subjected to 100% defoliation 1 or 2 times/year for 1 or 2 years

2003

2004

1 defoliation

4 defoliations