on each tree with pest mites and their eggs, and the
number of leaves with predators. There is no need to
count the mites. Once completed, compare the numbers
with the guidelines provided in the “Don't Treat” and
“Treat” columns on the sampling form provided at the
webspinning spider mite link of the UC Almond Pest
Management Guidelines (link above).
Many miticide options exist for cases where a
treatment is required. Each miticide has its strengths and
weaknesses, and for that reason options should be
discussed with a pest control advisor. More details on
miticide options can be found in the UC Almond Pest
Management Guidelines.
Final Thought
Sampling leaves to determine nutrient status for the tree
should occur after the onset of hull-split. This is usually
timed for mid-July. This timing has established critical
values based on monitored long-term tree performance
and identification of nutrient deficiency symptoms.
Pulling samples earlier (e.g. May or June) may help
identify micronutrient deficiencies, but do not provide
an understanding of tree macronutrient status. Mid-July
samples should be taken regardless of other leaf tissue
sampling periods.
An infestation of spider mites. Once webs begin to form, it is very challenging to reduce spider mite populations. Presence/absence
sampling should be done through May and June to determine most effective spray timings. Photo courtesy of David Doll.
David Doll,
UCCE Pomology
Farm Advisor
Merced County
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