IN YOUR ORCHARD
TIME TO CONSIDER
Kernel fill for Nonpareil will be completed by late May
to early June in the northern San Joaquin Valley. This
suggests that hull-split and harvest will occur in early to
mid-July, like last year, but later than the 2014-16 seasons.
This will impact nutrient, irrigation, and insecticide timings.
Every orchard will progress differently depending on
location and varieties, so it is important to monitor the
progression on an orchard basis.
Disease Management
By mid-May, the ability to control most diseases is
not possible. Summer foliar diseases such as rust and
Alternaria, however, may require treatment. A spray
model has been developed to assist in managing
Alternaria. It has been shown to be very effective in
and makes use of temperature and periods of leaf
wetness. Disease severity values (DSV) are assigned
for specific ranges of average temperatures during leaf
wetness periods during a day. Fungicides applications
occur if the accumulated index values over a seven day
period reach a value of 10 or higher. A weather station
and a leaf wetness sensor should be installed to help
calculate the DSV. More information can be found at
ucipm.ucdavis.edu.
Rust problems have increased over the past years due
to tighter spacings, later rainfalls, and more frequent
irrigations. Earlier applications of fungicides are the
most effective, but early June timed sprays may be
needed – especially if late rains occur. Most fungicides
are effective in controlling rust. Applications should
be made before symptoms are found throughout the
orchard – the earlier the better. Sprays made after July
usually have no effect in reducing the occurrence of rust.
Treatment for other diseases such as anthracnose,
bacterial spot and scab are not effective at this time.
These applications should have occurred earlier in the
season to reduce populations. Applying material now
for these diseases may help with sleep but will provide
no reduction of crop loss or leaf drop. If these diseases
are observed, take note and address them in the
dormant or in-season of 2019.
Irrigation Prior to Hull-Split
Research has shown that a mild to moderate water
stress applied prior to and maintained through the first
week of hull-split may help with harvesting and reduce
hull rot. This practice is known as regulated deficit
irrigation (RDI). Irrigation durations should be reduced
and plant stress should be monitored using the pressure
chamber until a stem water potential of -15 bars is
achieved. Depending on soil and irrigation practices,
this may take a few days to several weeks and may
require a 10 to 50 percent reduction in water applied.
The moderate stress should be maintained for two
weeks before the onset of hull-split. Once hull-split is
progressing, then full irrigation should resume until the
pre-harvest programs begin.
Operations successful with the application of RDI
typically begin to cut water at a small percentage
(10 to 20 percent) after the completion of kernel fill and
three to four weeks prior to hull-split. As stress and soil
moisture levels are monitored, the water reduction is
adjusted. Heavy soils may require a larger initial reduction
and a longer duration of curtailment. Soils with a lower
water holding capacity or under-irrigated orchards may
have a smaller or shorter period of reduction.
Almond kernel development nearing completion within a
'Nonpareil' almond. Photo courtesy of David Doll.
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A L M O N D F A C T S
