Pesticide and Environmental Update
New Control for Whiteflies Discovered
Whiteflies are very, very tiny. Under a magnifying glass, they resemble
moths—but from afar they look like wispy snowflakes.
While whiteflies may be small in stature, they can be deadly as a pest.
They suck and feed on the juices of hundreds of host plants—crops,
ornamentals, and weeds. Heavy feeding can give plants a yellow, mottled
look and eventually kill them.
cause major crop losses, both directly by feeding, and indirectly by
transmitting plant viruses. Use of pesticides to control them is
unsatisfactory because of their built-in natural resistance, the need for
repeated applications, and the potential hazard some insecticides may pose
to other living things or to the environment.
Fortunately, ARS scientists, led by Enrique Cabanillas, an entomologist
in the Beneficial Insects Research Unit (BIRU), at Weslaco, Texas, may be
on the verge of a major biological control breakthrough. Working under the
supervision of Walker Jones, entomologist and former research leader of
BIRU, Cabanillas has discovered a promising anti-whitefly fungus.
Isolated by Cabanillas in 2001 from infected whiteflies feeding on
eggplants, the fungus kills both larvae and adults of the silverleaf
whitefly, Bemisia argentifolii. Since 2001, it has periodically wiped out
whiteflies at the ARS insect-rearing facilities in Weslaco. This new
fungal species, Isaria poprawskii, was named in memory of the late Tadeusz
Poprawski, a former BIRU scientist known worldwide for his work on insect
pathology for microbial control of crop pests. He worked on whiteflies and
other target hosts in the region.
Detailed morphological, molecular, pathological, and ecological studies
have shown this fungus to be an entomopathogenic species—that is, one
that can parasitize insects and then kill or disable them. This work was
done by Cabanillas; Jones, currently director of the European Biological
Control Laboratory at Montpellier, France; microbiologist Richard Humber
of the Plant Protection Research Unit at Ithaca, New York; molecular
biologist Jesse de León of BIRU; and molecular biologist Dan Murray of
the Honey Bee Research Unit at Weslaco.
Further studies conducted by Cabanillas and Jones indicate that I.
poprawskii also harms larvae and adults of the glassy-winged sharpshooter,
Homalodisca vitripennis, the main vector of the bacterium that causes
Pierce’s disease, which is destroying grapevines in parts of California.
In addition to its potential to fight two major insect pests, other
remarkable features of this fungus include its natural establishment in a
semiarid region where temperatures reach 107°F; its persistence even in
the absence of insect hosts; and its high spore production in common
culture media, which makes it comparatively easy to grow in the
laboratory. These features suggest that the fungus could be a promising
candidate for practical biological control of the silverleaf whitefly and
the glassy-winged sharpshooter.—By Alfredo Flores, Agricultural Research
Service Information Staff.