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Encarsia
perniciosi was introduced to New Zealand
accidentally. It was already present in the country in
1959 when an attempt was made to supplement its
effectiveness by introductions of Californian and Russian
strains of E. perniciosi via India. It is an
endoparasite, developing inside the host scale insect. It
is probably one of the more important natural enemies of
San Jose scale in New Zealand, being common throughout
the country and causing high parasitism in some
populations. New Zealand populations are almost entirely
female. A study in Nelson indicated that this species
became the dominant parasitoid in an apple orchard over
several seasons after the cessation of spraying. The
importance of E. perniciosi in the biological
control of San Jose scale is recognized in many
countries, and attempts have been made to breed it for mass release.
Most organophosphate and carbamate insecticides are known
to be toxic to E. perniciosi, whereas a number
of fungicides have been shown to be safe or of low
toxicity.
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