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Darwin Mechanical Blossom Thinning Update

Several peach orchards in Ontario were blossom-thinned in the Spring of 2009. Data was collected with positive results removing 30-40% of the bloom on average.

Goals of the project were to:

• Analyze and compare the effectiveness of the Darwin to remove peach blossoms using different orchard training systems, tractor speed, string orientation, rotation speed of the strings, etc.
• Record the economic benefit for thinning peaches comparing the Darwin to hand thinning
• Measure any differences in yield, fruit size and number of split pit fruit per tree
• Follow-up harvests and hand thinning times were recorded later on in the summer. Highlights include:
• At one site, a section of 5 trees from two rows was hand-thinned 5 weeks after bloom. The hand thinners from the Darwin row removed only 469 fruit compared to 743 from the adjacent hand row (37% less fruit needed to be removed). The average fruit weight of the Darwin- thinned fruit was 9.37 grams compared to 8.77 grams from the hand thinned row (6% larger).
• Thinning times at most sites were reduced by about 40% per tree.
• At one site, Garnet Beauty trained to open center in a side by side demonstration, produced almost exactly the same yields per 25-tree row, but the fruit size on the Darwin-thinned trees was 140 grams per fruit compared to 126 grams per fruit (an 11% increase).
• However, the number of split spit fruit was 4.7% compared to the hand thinning at 2.3% during an unusually wet growing season.
• At another site, "Allstar™" peach was trained to a high density spindle vertically trained system in a replicated trial. Yields were almost identical per tree but fruit size was 159 grams for the Darwin treatment (18 strings at 180 rpm) and 145 grams for the hand-thinned treatment. The percent split pit fruit was almost identical 7.2% for hand versus 7.4% for Darwin. 3 other Darwin treatments with different string arrangements also had larger fruit but were over-thinned resulting in 9 to 18% less yield and 7.6% to 13.4% split pits.

Most of the results have been positive for growers using the Darwin in commercial orchards. Future peach trials will continue in 2010 as growers look forward to new technology to reduce labour costs in the orchard and increase profitability. Look for more information in newsletter updates and at the Ontario Fruit and Vegetable Convention 2010.