Girdling: What is girdling? A Sustainable Method for Increasing Fruit Tree Yield Dr. Lauren C. Garner Horticulture and Crop Science Department California Polytechnic State University San Luis Obispo The Trunk What is girdling? What is girdling? Why girdle? Influencing fruit set, size, total yield, harvest date… Grapes Peaches Apples Removal or restriction of a strip of bark Citrus 1 What about the avocado? Avocado Girdling Study Objective determine effects of girdling on growth and physiology of ‘Hass’ avocado Treatments Control (no girdling) Girdled pre-bloom (November) Girdled at full bloom (March/April) Girdled at peak fruitlet abscission (June/July) Effect of Girdling at Full Bloom on Final Percent Fruit Set 1 0.9 Seeded Fruit All Fruit 0.8 0.7 0.6 0.5 Untreated 0.4 Girdled Fruit set (%) set Fruit 0.3 0.2 0.1 0 Trial 1 Trial 2 Trial 1 Trial 2 α = 0.50 0.07 0.07 0.01 α value for 2-sample Wilcoxon rank sum tests 2 Effect of Girdling at Peak Fruitlet What DIDN’T Happen in Response to Abscission on Final Percent Fruit Set Girdling ? 16 Girdling did not result in a reduction in 14 Seeded Fruit All Fruit fruit size in terms of mass, length or 12 diameter. 10 8 Untreated Girdling did not result in a change in Girdled Fruit set (%) set Fruit 6 seed size in terms of mass or diameter. 4 There was no inverse correlation 2 0 between fruit size and fruit number per Trial 1 Trial 2 Trial 1 Trial 2 branch. α = 0.01 0.30 0.001 0.01 α value for 2-sample Wilcoxon rank sum tests What DIDN’T Happen in Response to Girdling ? Indeterminate Inflorescences The treatment did not significantly affect fruit size or retention of the preceding year’s crop. Uses in Sustainable Agriculture Spatial and temporal changes in resource allocation due to girdling result in increased avocado yields without detrimental side effects. Applications… 3.