decline during the fourth growing season may have been
infected prior to or after planting in the orchard. Those
declining in later years were infected after the trees were
planted.

Nectarine Pest Control

Nectarines are identical to peaches except that they
lack pubescence (fuzz). Most management practices are
similar with peaches and nectarines. Pest control with
nectarines is frequently more difficult than with peaches.
Pests, which attack the fruit, are generally the ones
causing most concern, but those attacking the foliage may
also be more difficult to control. The two diseases that
are more troublesome on nectarines are brown rot and
bacterial spot. Similarly, Thrips, aphids, and Japanese
beetles are frequently more troublesome on nectarines.
Russet of the fruit skin is also much more of a
problem on nectarines. The smooth skin of the nectarine
subjects the fruit to considerable russet in most years. The
causes of russet are similar to that which causes russet on
Golden Delicious, i.e., cold weather from pink into the
early cover sprays when the fruit have a coating of
moisture. Russet is related to both weather conditions and
the pesticides used during this sensitive period. Most of
the russet is superficial and the fruit is graded as U.S.
Fancy.
There are probably many reasons why many nectarine
varieties are more susceptible to pest attack. The
principal ones appear to be an increased genetic
susceptibility to somepests and the absence of the
protection that fuzz provides. The principles and control
strategies discussed for brown rot are probably applicable
to the other pest problems encountered in nectarine
production.
A partial explanation of the increased susceptibility of
many nectarine varieties is that many of the higher quality
nectarines were developed in California where brown rot is
not a serious problem. Thus, these varieties were
probably not rigorously screened for brown rot tolerance.
The nectarine fruit, being smooth, does not have a great
amount of surface area, as do peaches with their hairy
surface. Thus, the fruit surface cannot retain rates of
pesticides, to provide the protection against pest attack,
that the peach does. This deficiency can probably be
corrected through the use of effective spreader-sticker and
improved spray practices to ensure better coverage and
retention.
Nectarine fruit, like all smooth-skinned members of
the genus Prunus, are subjected to "latent infections,"
whereas peach fruit have never been shown to be similarly
affected. Latent infections generally occur during the
bloom period and remain confined to a tiny number of
cells beneath the skin surface for extended periods. As the
fruit increases in size, the chemical composition changes.
The chemical changes occurring in the fruit result in
susceptibility to the brown rot fungus. At this time, the
fungus starts to grow and soon becomes visible as a
brown rot infected fruit.

This is generally the time that growers become more
concerned about brown rot and they initiate a more
vigorous spray schedule. Unfortunately, sprays are much
less effective, since the infection occurred in the bloom
period. A more effective approach would include the use of
highly effective fungicides from pink through petal fall,
together with better spray coverage and timing.
Russet of the fruit also contributes to increased brown
rot, since nutrients are exuded through the cracks in the
skin. The spores of the brown rot fungus will not
germinate without an external supply of nutrients, and the
cracks in the skin provide all that is needed for spore
germination and infection.
Blossom blight and early fruit infections with the
brown rot fungus generally result in extreme difficulty in
control of the disease just before and after harvest. In a
casual evaluation of the peach and nectarine variety block
at Cream Ridge during the spring of 1987, several
varieties of nectarines had more than 80 percent of the
blossoms infected with blossom blight, while none of the
peach varieties had more than 25 percent blighted
blossoms. Further, when examined during the summer,
the cankers produced from infected blossoms on nectarine
varieties appeared to be actively sporulating all summer
long, whereas those on peaches appeared to become
inactivated by mid-summer. These observations suggest
that some nectarine varieties may prove to be a better host
for overwintering of the fungus.
Similar principles and altered control practices could
be provided for others pests, but to conserve space they
will not be listed. To prevent pest problems from
developing on nectarines, consider the following
suggestions.
[!]Where possible, select varieties with high levels of
resistance to pests. See list of varieties in "Peaches
and Nectarines" section.
[!]Use the most effective pesticides at the proper rate and
proper time from pink through petal fall.
[!]Employ practices, which will improve spray coverage
and retention, including the use of spreader stickers.
[!]Attempt to evaluate and delete pesticides, which
increase fruit russet.
Many growers are successfully producing high quality
nectarines at the present time. Such growers are
encouraged to continue utilizing those practices that have
proven successful.

Nematode Control

Detecting. Whenever nematode damage is suspected
and especially before planting young trees, an examination
of both soil and roots is recommended. Soil and root
samples must be adequate in size and collected in a
manner that will make evaluation possible. The following
suggestions are made so those samples will be collected
properly and arrive at the Nematode Detection Laboratory
in good condition.
Samples for nematode analysis will not be processed
unless the following instructions are observed:

1998 New Jersey Commercial Tree Fruit Production Guide

109