7
14 days. If there are three thrips per
trap each week, there is a 50/50
chance mite populations will be
the same or lower in 14 days.
Necessary treatments? Apply
with caution
Growers now have a number of
reduced-risk, selective miticides
available, and Almond Board-funded
research has led to the development
of presence/absence monitoring
thresholds for both mites and their
natural predators to help almond
growers understand exactly when they
need to pull the trigger on treatment.
When treatment is required, a single
miticide application that is tank mixed
at hullsplit, or two weeks after, is
typically sufficient for seasonal control.
Lightweight oil can also be a good
IPM substitute in mite tank mixes.
In their efforts to preserve predators
of mites, growers should be cautious
about insecticides used against
navel orangeworm. Broad-spectrum
insecticides, such as pyrethroids,
can disrupt a wide range of natural
enemies. Care should also be taken
to avoid selective insecticides
and miticides that are known to
impact thrips. The use of selective
insecticides that do not affect natural
enemies can ensure that natural
enemies provide maximum mite
control during harvest, long after the
residual impacts of miticides are gone.
Roseman said ongoing research will
continue to refine treatment thresholds
and recommendations based on the
presence or absence of mites and
six-spotted thrips.
Dust's role in mite control
Because dust can exacerbate
mites, managing dust at harvest is an
important component of mite control.
To reduce the risk of aggravating
mites, growers should maintain a
ground cover or clean orchard floor
to increase the efficacy of specific
strategies for reducing harvest dust,
strategies that have been developed
through ongoing research funded by
the Almond Board. These dust control
tactics include:
Reducing blower passes
where possible
Setting sweeper heads to an
optimum height so that the tines
are 0.125 inch off the ground
Reducing harvester ground speed,
particularly in orchards with
loose soils
Reducing separator fan speed to
the lowest extent possible
For more information on how
to reduce dust during harvest to
strengthen mite control, visit
Almonds.com/HarvestDust and check
out the University of California's Year-
Round Almond IPM Program at
IPM.UCANR.edu/Agriculture/Almond.
Managing dust at harvest is key to controlling mite levels. Growers and custom harvesters should set their sweeper heads to an optimum
height to prevent unnecessary dust kick-up as they make their passes.
1
https://www2.ipm.ucanr.edu/agriculture/
almond/Webspinning-Spider-Mites/
