Seed Beetle May Check Spread of Jerusalem
Thorn By Jesús García
December 28, 2000
Service scientists in Argentina have recently completed basic research on
the usefulness of the Parkinsonia seed beetle as a biological control agent for
Parkinsonia aculeata--the Jerusalem Thorn tree.
Researchers at ARS
South American Biological
Control Laboratory in Buenos Aires, Argentina, have found that the
Parkinsonia seed beetle--Penthobruchus germaini--may be able to control
the spread of this invasive tree by depositing its eggs in the trees
seedpod. Once the eggs hatch, the larvae burrow into the trees seeds to
feed and complete their development.
The Jerusalem Thorn tree is native to northern Argentina, where
natural controls keep it in check. In the southwestern United States, however,
it has no natural enemies and has spread across rangelands from southern Texas
to Arizona and northern Mexico. In Australia, the tree was imported as an
ornamental. Now its become an invasive weed in Australian pastures and
rangelands, as well as in the countrys most productive grasslands in low
areas and along streams.
Preliminary indications are that P. germaini appears to
have the necessary characteristics to be an effective biological control agent
for the Jerusalem Thorn tree. In field studies, the beetle was found to infest
one out of every four seeds in one season.
Since P. germaini develops in the relatively short time
period of 48 days, two generations of beetles would be available as biological
control agents each year. Its cold tolerance, high egg fertility and low rate
of natural parasitism are also highly desirable attributes. The tests also
indicate that the beetle is host specific to Parkinsonia aculeata.
Preliminary field evaluations in Australia--where P. germaini was
introduced in 1995--indicate that the beetle is destroying a high percentage of
P. aculeata seeds.
This study is part of the Agricultural Research Services
effort to find nonchemical pest control alternatives. ARS is the
U.S. Department of Agricultures chief
scientific research agency.
Scientific contact: Juan Briano, USDA-ARS South American
Biological Control Laboratory, Buenos Aires, Argentina, phone 54-11-4662-0999,
fax ext. 104, email@example.com