7898

• UCREFRP Catalog Number: 7898
• Author: Swadener, C.
• Title: Insecticide Fact Sheet,
• USFW Year: 1994
• Copyright Material: YES

.;

.JOURNAL OF PESTICIDE REFORM1FALL 1994. VOL.14. NO.3

magnitude after 2 weeks, but then remained
constant for 8 months following applica-
tion.49
B.t. does not appear to move readily in
soil. In one study, two varieties of B.t. were
applied in adjacent plots, but did not be-
come cross-contaminated, indicating that
B.t. does not move laterally in soil.2.8 Other
studies found that B.t. was not recovered
past a depth of 6 centimeters after irrigation,
and that movement beyond the application
plot was less than 10 yards.7,50
Foliage: B.t. deposited on the upper side
of leaves (exposed to the sun) may remain
dFecrive for only 1-2 days, but B.t. on the
underside of leaves (Le. protected from the
sun) may remain active for 7-10 days.2.8 It
is possible for it to be significantly more
persistent, however. Viable spores of B.t.k.
were recovered from white spruce foliage
one year after application.51 In one experi-
ment conduaed in Japan, B.t. persisted for
two years in a citrus orchard and remained
toxic to caterpillars.52
Water: B.t:k. has been recovered from
rivers and public water distribution systems
after an aerial application ofThuricide 16B.
Standard water treatment processes are not '
adequate to destroy B.t.k. spOres.53
B.t.i. spores and cryscils bind readily to
sediments in the water column,54.55 which
reduces their efficacy by making them inac-
cessible to mosquito and blackfly larvae.
In one test, B.d. was applied to water,
then allowed to contaa mud parrides. Over
99 percent of the B.t.i. spores were found
in the mud, rather than in the water, after
45 minutes. The B.t.i. retained viability and
toxicity for at least 22 days, killing 90 per-
cent of the mosquito larVae when the mud
was stirred and reintroduced to the water
column. 54
In another experiment, viable cells were
recovered from the water for up to 200
days and in the sediment for up to 270
days after application.55
Air: B.t.k. has been found to drift over
3,000 meters downwind during an aerial
application. The distance B.t.k. is capable
of drifting depends upon the amount and
method of application,56 as wdl as the di-
matic conditions. B.t. thuringimsis was
measured in air for up to 17 days following

an application.4

Biotechnology

Examples of generic manipulation and
genetic engineering with B.t. include the
following:7 .
· In the agricultural produa Foil, the
gene for a toxin with activity against beetles
was transferred through conjugation (sexual
reproduction in bacteria) to a B.t.k. cell
that only affected butterflies and moths. The
resulting cell showed insecticidal properties
against beetles, butterBies, and moths. Since

" During the 1992
Asian gypsy moth
spray. program in
Oregon., a woman
who was exposed to
Foray 488 had a
preexisting allergy
to a carbohydrate.
that was present as
an inert ingredient.
Within 45 minutes of
exposure, the
woman suffered
from joint pain and
neurological
symptoms."

EP A considers the organisms resulting from
conjugation to be generically manipulated
rather than genetically engineered, Foil was
registered for use in the U.S. in 1990.
· PSroMmonas jlUOfflCens cells can be
engineered to produce the B.t. ddta-endot-
oxin without produaion of a spore. The
crystal protein remains inside the P.
fluorescens cell wall. In the products MVP
and M-Trak, the P. fluorescenscell is killed
after it produces the crystal protein. When
the produa is applied, the ddta-endotoxin
remains protected within the now dead cell
wall. In this way, the B.t. ddta-endotoxin
retains its effectivencss for two to three rimes
longer than other B.t. formulations. MVP

and M-Trak were the first genetically engi-
neered products to be registered by EP A,
since the transgenic organism was not alive
when rdeascdinto the environment.
· B.t.i. used ro control mosquito and
blackBy larvae that live on the water surface
begins to sink, away from the target Iarvae.
within 24 hours. Bacteria that nacurally live
on the water surface (in the same environ-
ment as mosquito or blackBy larvae), have
been engineered to produce the B.d. crys-
tal proteins.
· . Over thirty different crops have been
engineered to produce the B.t. crystal pro-
tein throughout their plant structure. Any
pcscthat feeds on any part of these plants
will be exposed to the B.t. delta-endotoxin, .
and those susceptible to the toxin will be
killed.
dearly. the possibilities for the genetic
engineering of B.t. ddta-endotoxins seem
endlcss. However, researchers know so little
about the ecology and genetic stability of
B.t., that the potential ecological effects of
these cransgenic organisms are impossible
to predia with certainty.

Resistance

Scientists once thought that the mode
or action of B.t, was complex enough to
prevent the devdopment of pest insect re-
sistance. However, rime and further research
proved this to be untrue. Eight insect species
have been studied because of their. ability
to devdop resistance to B.t.57 The Indian
meal moth, a pest of grain storage areas,
was the first insect to devdop resistance to
B.t.k.58 in laboratory experiments. Resistance
progresses more quickly in laboratory ex-
periments than under fidd conditions due
to higher sdecrion pressure in the labora-
tory.59 No indications of insect resistance
to B.t. were observed in the fidd, until the
devdopment of resistance was observed in
the diamondback moth in crops where B.t.
had been used repeatedly. Since then, resis-
tance has been observed in the laboratory
in the tobacco budworm, the Colorado po-
tato beetle and other insect speciesY The
gypsy moth also shows potential for devd-
oping B.t. resistance. 60 Some insects, such
as the diamondback moth and the tobacco
budworm, eXhibit resistance to multiple B.t.

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