Raleo De Durazno

Use of a String Blossom Thinner in Canning Peaches: Year One
Roger Duncan & Maxwell Norton
University of California Cooperative Extension

Hand thinning can cost $1200 per acre or more in extra early varieties Ladder falls are very common workers’ comp claim

Darwin String Thinner
•Developed in Germany for blossom thinning apples •Penn State CE tried it in peaches with some success•Multi-state research project funded by the Specialty Crops Research Initiative & the CA Canning Peach Association

Molded plastic cords can be removed or cut for different thinning effects

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Preliminary Trials in 2009
• Nine “demonstration” trials in Stanislaus County • Two in Merced County
– Single row or four row “picking units”

• Two fully replicated, intensive field trials– Six replications of 10 ten trees each

Participating Stanislaus County Growers
• Norman Kline
– Loadel (replicated and demo trials)

• Derk & Paul Van Konynenburg
– – – – Tuolumne (replicated & demo trials) Loadel Carson Ross

• Sid & Scott Long
– Reigel

• John and Chris Miller
– Bowen

• Kevin Voss
– Loadel – Stanislaus

Replicated Trials

Hangers were tagged to countflowers before and after blossom thinning and again after fruit set

Crews were timed to determine the time required to hand thin in blossom-thinned and unthinned trees

Fruit were collected at hand thinning time to determine number of fruit thinned and measure fruit size

B-VK Tuolumnes
• • • • • • • • Perpendicular “V” 6’ x 18’ ~ 10 years old “Renewal pruned” Thinned tops & both sideswith string thinner Tractor speed: 1.5 MPH Spindle speed: 200 RPM Bloom stage: late petal fall

B-VK Tuolumnes

B-VK Tuolumnes

Bloom stage of B-VK Tuolumnes when thinned

Effect of Darwin String Thinner on Hand Thinning Costs
B-VK Tuolumnes. April 30, 2009.
Thinning Time (hours / acre) Check Darwin Thinning Cost ($ / acre)* Check Darwin Reduction in thinning costs $$

118.592.0

$1328

$1031

$297

Effect of Darwin String Thinner on Hand Thinning Costs
B-VK Tuolumnes. April 30, 2009.
Thinning Time (hours / acre) Check Darwin Thinning Cost ($ / acre)* Check Darwin Reduction in thinning costs $$

118.5

92.0

$1328

$1031

$297

*Hand thinning costs based on $11.20 per hour ($8.00 + 40%)

Effect of Darwin String Thinner on Hand Thinning CostsB-VK Tuolumnes. April 30, 2009.
Thinning Time (hours / acre) Check Darwin Thinning Cost ($ / acre)* Check Darwin Reduction in thinning costs $$

118.5

92.0

$1328

$1031

$297

*Hand thinning costs based on $11.20 per hour ($8.00 + 40%)

Harvest Evaluations •Fruit Size •Yield

Harvest Evaluations
•Determine fruit size, percent #1, #2, undersize, total yield

B-VK TuolumneHarvest Data
July, 2009

No. 1 Check 24.3

Tons per Acre No. 2 Smalls 1.2 (5.1%) 0.3 (1.3%)

Total salable* 25.5

*Total salable = number 1 fruit + < 5% number 2 fruit

B-VK Tuolumne Harvest Data
July, 2009

No. 1 Check Darwin 24.3 28.0

Tons per Acre No. 2 Smalls 1.2 (5.1%) 0.7 (2.4%) 0.3 (1.3%) 0.1 (0.4%)

Total salable* 25.5 28.7

*Total salable = number 1 fruit + < 5% number2 fruit

Preharvest Fruit Counts B-VK Tuolumnes
Average number of fruit per tree Darwin Check 360 359
*Target ~ 275 – 300 fruit / tree Counted 24 trees in each treatment

Effect of Darwin String Thinner on Yield & Gross Income
Yield (tons per acre) Gross Income ($ / acre)*
Difference in Gross $$

Check Darwin Check Darwin Tuolumne 25.7 28.7 $8173 $9127 +$954

*Based on price of $318/ ton for Tuolumnes

Kline Loadels
• • • • • • • • Perpendicular “V” 6.5’ x 18’ 9 years old “Renewal pruned” Thinned tops & both sides with string thinner Tractor speed: 1.5 MPH Spindle speed: 200 RPM Bloom stage: 50-60% bloom

Norman Kline Loadels

Norman Kline Loadels

Bloom stage of Kline Loadels when thinned

Effect of Darwin String Thinner on Hand Thinning Costs
Kline...