Agriculture Reference
In-Depth Information
in reducing the amount of hand thinning needed. For large commercial orch-
ards, reducing the amount of labor required to thin fruit often makes a large
economic difference.
Shakers and string thinners.
Commercial growers are adopting shakers and
string thinners for peach production. In research trials, these methods pro-
duced more consistent and effective results than did the chemical thinners
tested, and they increased fruit size and greatly reduced the amount of
follow-up hand thinning that was needed. In Pennsylvania trials, the drum
shaker reduced crop load more than all of the other treatments, produced
fruit of a similar size to the fruit that was string thinned, and required about
15 worker hours per acre for follow-up hand thinning. The string thinner also
increased average fruit size and reduced the variability in fruit size. About 22
worker hours per acre were required for hand thinning after using the string
thinner. Blocks that were thinned only by hand required about 40 worker
hours per acre of thinning.
So far, researchers have noted little damage to the trees when using
mechanical thinners, except for damage done by string thinners to large
limbs sticking out into the alleys. Most of the trials have involved relatively
flat canopies, primarily quad-V and perpendicular-V training systems. The
overhead string thinner can be used with any training system, but it will not
be effective in thinning fruit in the lower canopy. For large peach and nec-
tarine orchards, the most effective approach will probably involve using a
combination of a vertically mounted string thinning at 20 percent bloom fol-
lowed by shaker thinning 40 to 55 days after full bloom.
Chemical sprays.
Chemical thinning in research and commercial orchards
has proven less reliable with stone fruits than with apples and pears, al-
though recent research shows some promise for developing effective chem-
ical thinners that can be used in organic orchards. Vegetable oil emulsions
applied to the dormant buds have produced some thinning and increased
fruit size. In Pennsylvania research trials, a caustic fertilizer (ammonium
