New Fungal Finding Could Mean Better
Bio-Insecticide By Jan Suszkiw September 4, 2008
A method of culturing the beneficial fungus Metarhizium anisopliae so
that it churns out billions of tightly bundled cells, called "microsclerotia,"
could mean even more moldy mayhem for soft-bodied ticks, termites and crop
pests including sugar beet root maggots.
Until 2004, Metarhizium wasn't known to produce the
microsclerotia--among the toughest forms this fungus can take to tolerate
adverse conditions. Indeed, only plant-disease fungi were thought to produce
these sturdy cells. But now that the "secret" is out,
Agricultural Research Service (ARS)
scientists aim to exploit the information to develop new, improved
bio-insecticide formulations containing the fungus.
For more than a decade, bio-insecticide makers have formulated
Metarhizium using conidia or other spore forms. But mass-producing them has
been time-consuming and labor-intensive. Conidia-based formulations have also
suffered from poor shelf life and field survival once applied, according to
Jackson. He works at the ARS
Center for Agricultural Utilization Research in Peoria, Ill.
Jackson's studies with ARS entomologist
Jaronksi show that using microsclerotia instead of conidia can cut the
costs and time involved in formulating the fungus and can significantly improve
its shelf life and pest-fighting performance.
For example, in studies led by Jaronski at the ARS
Management Research Unit in Sidney, Mont., conidia-only granules of
Metarhizium germinated seven to 10 days after being applied, versus four days
with microsclerotia-based formulations. The scientists were also able to
produce the microsclerotia in four days, compared to two weeks for conidia. And
during 2007 field trials, sugar beet root maggots inflicted far less feeding
damage to microsclerotia-treated beets than to ones treated only with conidia.
Another advantage, according to Jaronski, is that the microsclerotia
can be formulated into granules and sized more easily than other spore forms.
This should make the microsclerotia more compatible with farmers' seed planters
and pesticide granulate applicators.
The fungus infects and kills only certain insect hosts, and is never
harmful to people, pets or livestock.
about this research in the September 2008 issue of Agricultural Research
ARS is a scientific research agency of the
U.S. Department of Agriculture.