TIME TO CONSIDER
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Almond Facts
MAY | JUNE 2016
Time To Consider
DAVID DOLL, UCCE Nut Crop Pomology Farm Advisor, Merced County
Almond kernel development is ahead of schedule. Kernel fill for Nonpareil was completed in many
locations of the northern San Joaquin Valley around mid-May, suggesting that the season is progressing
two to three weeks ahead of “normal.” This means that hull-split and harvest will occur earlier than
normal, impacting 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.
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. 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.
Be careful not to over-stress the trees. Too much stress
during the hull-split period can decrease kernel weights and
cause “textured” kernels. If trees have been deficit irrigated
through the season due to drought conditions, RDI is not
advised. More information can be found in Publication
#8515, “Drought Management for California Almonds,”
available for free at
/.
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. Applications
for alternaria should follow the DSV model highlighted
at ucipm.ucdavis.edu. This model takes into account
leaf wetness and duration to time preventative sprays.
It has been shown to be very effective in high alternaria
occurring areas. Rust problems have increased over the
past years due to tighter spacings and more frequent
irrigations. Earlier applications of fungicides are the most
effective, and summer sprays are typically only needed
when rain occurs or early infections are observed. Most
fungicides are effective in controlling rust.
Figure 1: Almond kernel development
nearing completion within a ‘Nonpareil’
almond.
Photo Credit: David Doll.
Continued on page 34.
