Agriculture Reference
In-Depth Information
thiosulfate) and various surfactants normally used in pesticide applications
were tested and found to produce less consistent results than mechanical
thinners. Organic oils applied with synthetic surfactants have shown prom-
ising results, but these materials cannot be used in organic orchards. While
ongoing research shows some promise, no effective chemical thinners are yet
available for organic peach and nectarine production.
Hand thinning.
Hand and pole thinning, whether used alone or as a follow-up
to mechanical thinning, remains the standard for peach and nectarine pro-
duction. Begin hand and pole thinning after June drop, which is usually about
5 to 8 weeks after full bloom. Start with the earliest-maturing varieties.
apart (6 to 12 fruits per 36 inches of fruiting wood), although you can find
other recommendations for wider spacings up to 8 inches apart. Much de-
pends on the intended use of the fruits and the variety. Although counterin-
tuitive, small-fruiting varieties require wider spacing than varieties that nat-
urally set larger fruit. You might want to space fruit intended for fresh use
somewhat farther apart than fruit intended for processing. Vigorous, well-
exposed 1-year-old wood produces the largest and best fruits. Remove most
or all of the fruits from thin and shaded wood.
In general, try to leave 30 to 40 full-sized leaves for each peach or nectar-
ine on the tree. With a little counting and practice, you can visually estimate
the numbers of fruit to leave. If the load is unbalanced and only part of the
branches bears heavy crops, you might need to do little or no thinning. The
goal is to adjust the crop load for the entire tree.
In commercial orchards, hand thinning is complex and based on total crop
load, leaf surface, tree spacing, and tree health. The science behind the pro-
cess is that it takes a certain amount of leaf surface to set and fully mature
a high-quality peach of a given size. The process is very sophisticated in the
clingstone peach industry, where the fruit is destined for canning.
Experienced growers of commercial processing peaches, for example, can
accurately develop uniform peaches of a particular size by leaving a certain
