Organic Peaches in Virginia?
Issues:
No harvest in previous year due to: Brown Rot, Peach Tree borer,
Lesser Peach Tree borer, Plum curculio and Black knot
Actions taken in 2009:
Cultural:
-
Pruned only branches showing
disease (black knot) or insect infestation (lesser peach tree
borer).
-
Removed ground cover from beneath
tree to allow for clean-up of spore-producing waste.
-
Removed mounded soil from around
trunk, added layer of compost for nutrient value and as mulch, and
restricted play area from under tree to avoid additional compaction.
-
Lightly raked soil under tree at
regular intervals to break up any bacterial strands.
-
Watered during periods of low
rainfall.
-
Thinned crop to reduce number of
fruit but increase the size and health of remaining fruit. Guideline
was 1 peach per 6 inches on a branch, no two peaches on adjoining
branches closer than 2.5 inches. Removed approximately 4 five-gallon
buckets of green fruit.
Organic Chemical Treatment:
-
Sprayed with dormant oil in late
winter for general insect suppression.
-
To control brown rot and plum
curculio: Began spraying at Pink stage (buds just turning pink).
Sprayed with mixture of 3 TBS. wettable sulfur plus 3 Cups
Surround* per gallon of water. Sprayed top and underside of
leaves and also covered branches and fruit. The sulfur is a
fungicide and the Surround provides a barrier against insect and may
help prevent the spread of disease organisms.
-
To control peach tree borer: Hung
sticky traps with pheromones to attract clear-winged wasps which lay
eggs of peach tree borer.
Results:
The tree was covered with peaches
of good size. Quite a few peaches with brown rot were removed during
the season to slow the spread of the disease. Peaches were harvested
while still somewhat hard because it appeared that the brown rot was
beginning to spread. Peaches were still delicious.
76 pounds of peaches were delivered to Interfaith
Relief. All the garden workers enjoyed snacking on the
less-than-perfect peaches
*Surround
is the trade name for kaolin clay.
Kaolin is naturally occurring clay resulting from weathering of
aluminous minerals such as feldspar with kaolinite as its principal
constituent (ATTRA 2004). Kaolin is a common mineral, considered
“generally regarded as safe” (GRAS) by the U.S. Food and Drug
Administration. It is used as an anti-caking agent in processed foods
and an additive to cosmetics, toiletries and health products. It is
also used as an “inert” carrier in some pesticides, and enhances the
performance of some microbial products (Rasad and Rangeshwaran 2000).
This material has several modes of activity (Stanley 1998). Kaolin
acts as a physical barrier preventing insects from reaching vulnerable
plant tissue. It acts as a repellent by creating an unsuitable surface
for feeding or egg-laying. The uniform white film may also disrupt the
insect’s host finding capability by masking the color of the plant
tissue. Furthermore, particles of kaolin act as an irritant to the
insect. After landing on a treated surface, particles of kaolin break
off and attach to the insect’s body triggering an excessive grooming
response that distracts the pest.
Kaolin formulations have also been shown to suppress diseases in
greenhouse and field studies (Haggag 2002, Puterka et al. 2000, Glenn
et al. 1999), and to kill insects in stored grain (Mostafa and Al
Moajel 1991). Labeled products for these purposes are not currently
available in the US.
The use of Surround® (a trade name for kaolin clay) can increase
overall fruit yields in regions with high light and temperature levels
(Puterka et al. 2000). In these situations, it can act as an anti-transpirant,
reducing stress on the plant.
Material fact sheet, Kaolin clay, Cornell University.
http://www.nysaes.cornell.edu/pp/resourceguide/mfs/07kaolin.php
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