String Blossom Thinner Designed for Variable Tree Forms Increases Crop Load Management Efficiency in Trials in Four United States Peach-growing Regions

Abstract

<jats:p>Hand thinning is a necessary and costly management practice in peach (<jats:italic>Prunus persica</jats:italic>) production. Stone fruit producers are finding it increasingly difficult to find a workforce to manually thin fruit crops, and the cost of farm labor is increasing. A new “hybrid” string thinner prototype designed to adjust crop load in vase or angled tree canopies was evaluated in processing and fresh fruit plantings in varying production systems in four U.S. growing regions in 2009. Data were uniformly collected across regions to determine blossom removal rate, fruit set, labor required for follow-up green fruit hand thinning, fruit size distribution at harvest, yield, and economic impact. String thinner trials with the variable tree forms demonstrated reduced labor costs compared with hand-thinned controls and increased crop value due to a larger distribution of fruit in marketable and higher market value sizes. Blossom removal ranged from 17% to 56%, hand thinning requirement was reduced by 19% to 100%, and fruit yield and size distribution improved in at least one string-thinning treatment per experiment. Net economic impact at optimum tractor and spindle speeds was $462 to $1490 and $264 to $934 per acre for processing and fresh market peaches, respectively. Case study interviews of growers who thinned a total of 154 acres indicated that commercial adoption of string-thinning technology would likely have positive impacts on the work place environment.</jats:p>

Peach Blossom String Thinner Performance Improved with Selective Pruning

“…Follow-up thinning time for hand-thinned control trees was 78.3, 36.6, 30.7, and 19.3 hÁha -1 in the same trials. The follow-up hand-thinning data, along with bloom and fruit set data, confirm previous reports indicating the importance of careful assessment of bloom density to determine best use of mechanical thinning tech-nology (Baugher et al, 2009(Baugher et al, , 2010aSchupp et al, 2008).…”

“…1B) was used to thin open centertrained peach trees. This thinner, designed to thin peach trees of variable forms (Baugher et al, 2010a), has a 2.5-m-long spindle that tilts from 120°to 270°from vertical and can thus be oriented in either a vertical or a horizontal position. On both string thinner models, the spindle is powered by a hydraulic motor and speed is adjusted by a proportional flow control valve.…”

“…A 2008 prototype designed to operate in a horizontal position had similar effects on peach trees trained to an opencenter system (Baugher et al, 2009). The next year, a string thinner was manufactured that operated in either a vertical or horizontal position, and trials conducted in four peachproducing regions on both narrow vertical and open-center canopies demonstrated reductions in follow-up hand-thinning requirement and increases in yield and fruit size (Baugher et al, 2010a). Pennsylvania trials conducted with the hybrid thinner on both perpendicular V-and open center-trained trees at various bloom stages showed that the window for thinning peach and nectarine trees ranges from the pink to the petal fall stage of bloom development (Baugher et al, 2010b).…”

The use of agricultural robots in orchard management

“…String thinners were developed in the 2000s to mass remove flowers in high density fruit production systems (Baugher et al, 2010). String thinners are composed of a rotating spindle with plastic strings; the system is attached to a tractor which navigates through the rows in orchards.…”

Remote Sensing Techniques for Assessing Water Deficits and Modeling Crop Response

“…Comments from this survey confirm that tree fruit growers want to see technological benefits through on-farm trials, particularly in the eastern United States. Case studies of growers who borrowed machinery are generally positive and can help prioritize needs in overcoming adoption problems (Baugher et al, 2010;Llewellyn, 2007). Growers who use the equipment may also serve as reliable sources of first-hand knowledge, which will quickly diffuse information among members of local grower groups (Lamb et al, 2008).…”