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Schematic diagram of pear psylla populations showing importance
of reducing overwintering populations before egg laying occurs
in late January to early February.
Broken line represents a good IPM program
where dormant treatments were used to bring populations down below 1 adult
per 100 beats before egg laying. Populations can be maintained
below economic levels with normal summer sprays and naturally
occurring biological control.
Solid line represents a program
where at least 5 adults per 100 beats remained at egg laying time.
Populations can not be reduced even with additional sprays.
Substantial economic loss occurs (shaded area).
Illustration from Integrated Pest Management for Apples and Pears.
UC ANR Publication 3340.
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