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How to Manage Pests
UC Pest Management Guidelines
Pistachio
Pistachio Seed Chalcid
Scientific name: Megastigmus pistaciae
(Reviewed 2/07,
updated 2/07)
In this Guideline:
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DESCRIPTION OF THE PEST
The pistachio seed chalcid overwinters as a diapausing larva in infested nuts.
In spring the larva pupates, and the pupa transforms to an adult that chews a
tiny (1 mm) exit hole through the hard nut shell and emerges as the adult wasp.
Female wasps lay their eggs in the hardening shells
of maturing nuts in May and June, and the second adult generation emerges in
mid- to late-summer. Some of the larvae of this generation do not emerge as
adults the same year but remain in the nuts as mature larvae until the
following spring. Adult female wasps that do emerge in August and September are
able to oviposit through the hard shells of mature nuts, producing
overwintering larvae.
DAMAGE
Although the seed chalcid is not a pest of commercial plantings of pistachios
in California, it does occur throughout the Central Valley and is a pest in
other areas of the world where pistachios are grown. Growers should be aware of
this insect because it feeds directly on the pistachio nut and has the
potential to reduce yields. It has become a serious pest in some areas of
California where Pistacia seeds are produced for nursery rootstocks and in ornamental
pistachios planted in urban areas.
MANAGEMENT
Examine nuts for small holes that indicate a seed chalcid has emerged
from the nut. Adults can also be monitored by the use of yellow
sticky traps that are
placed in orchards in early August. Control of this pest consists primarily of
orchard sanitation: remove and destroy nuts left on the tree following harvest
as well as those that have fallen on the ground.
![[UC Peer Reviewed]](/IMAGES/logo-ucpeerreviewed.jpg)
UC IPM Pest Management Guidelines: Pistachio
UC ANR Publication 3461
Insects and Mites
W. J. Bentley, Kearney Agricultural Center, Parlier
R. H. Beede, UC Cooperative Extension, Kings Co.
K. M. Daane, Biological Control, UC Berkeley/Kearney Agricultural Center, Parlier
D. R. Haviland, UC Cooperative Extension, Kern Co.
Acknowledgment for contributions to the insect and mite section:
R. E. Rice, Kearney Agricultural Center, Parlier
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