The only US Bt company that manufactures its own products

Bacillus thuringiensis Life Cycle: Production of Spores and Crystals

Vegetative

Bt cells

10 m

Sporangium

Sporulation

Spore

Crystal

Spore Free spores &

crystals

Crystal

Lysis

“Bipyramidal”

crystal

(Typical of Btk; other

Bt’s may have

different crystal

types.)

Bt 101

Mode of Action of

Bacillus thuringiensis subsp. kurstaki

1

(Note: Not to scale)

4

3 6

5

pH=10 2

1. Larva ingests Bt.

2. Toxin crystals dissociate in alkaline midgut.

3. Protoxin molecules are released from dissociated crystal.

4. Protoxin molecules “activated” by the insect’s digestive enzymes.

5. Activated -endotoxin molecules bind to receptors on midgut cells.

6. Toxin destroys the cellular lining of the midgut.

7. Gut is paralyzed, insect stops feeding.

8. Death from osmotic shock, septicemia (spores germinate), or starvation.

Bt 101

Re

lative

To

xic

ity o

f

Ind

ivid

ua

l C

ry T

oxin

s

Spodoptera

Plutella

Trichoplusia

Heliothis

Toxicity of -endotoxins of Bacillus thuringiensis

to Important Lepidoptera pests Bt 101

Endotoxin Profiles of Bt spray products

for control of Lepidoptera

Deliver Bt kurstaki products

Javelin

DiPel

Biobit

Agree

XenTari Bt aizawai products

Mattch

CryMax

MVP

Lepinox

Genetically engineered products

Re

lative

% C

ry T

oxin

Co

nte

nt

Bt 101

The Cry Toxin “Spectrum”

BASICS Bt

Re

lati

ve

To

xic

ity o

f

Ind

ivid

ua

l C

ry T

ox

ins

Bt aizawai products

Bt kurstaki products

Re

lati

ve

% C

ry T

ox

in C

on

ten

t Product

profiles

Pest

Activity

Deliver

Dipel

Javelin

Xentari

Agree

Crymax

Cabbage Looper

Lepinox

Corn Earworm

Diamond

Back Moth

Fall & Beet Armyworm

• Broadest spectrum of high activity Cry1Ac

• Best Spodoptera activity Cry1C

• DBM resistance management Cry1C, Cry1D

Important Cry Toxins for Control of

Lepidoptera in Agriculture

Trichoplusia ni

Spodoptera exigua

Plutella

xylostella

Helicoverpa (Heliothis) zea

Bt 101

Label potencies of some Btk products

0

10

20

30

40

Deliver

41 BIU

CryMax

29 BIU

Javelin

17 BIU

DiPel

2X/DF

14.5 BIU

Agree

11 BIU

DiPel ES

8 BIU/pt

BIU = Billion International Units

Bt 101 B

IU p

er

po

un

d

• Cry toxin complement and concentration

• Presence/absence of other potency factors

Synergists (spores, zwittermycin, VIP’s)

Centrifugation vs. spray drying

• Formulation quality

Suspensibility

Particle size

“Inert” ingredients (UV screens, surfactants)

Performance Characteristics of

Sprayable Bt Products Bt 101

Physical Characteristics of Some Commercial

Bacillus thuringiensis Formulations

Certis USA

Javelin® WG

Deliver® WG

Agree® WG

Valent BioSciences

DiPel® 2X WP

XenTari® WG

Ecogen

Lepinox® WDG

CryMax® WDG

87.4

86.5

80.4

79.1

75.7

74.4

53.7

Manufacturers

& Products

5.1

5.9

30.1

37.7

45.9

83.5

86.4

Suspensibility

(%)

Median particle

diameter (m)

Bt 101

Potential for Cross-Resistance of Diamondback Moth

(Plutella xylostella) to Different Insecticides

Shelton et al., J. Econ. Entomol. 93:931-936 (2000).

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Corr

ela

tion b

etw

een tole

rance r

atios

(Pe

ars

on

’s c

orr

ela

tio

n c

oe

ffic

ien

t)

Em

am

ectin b

enzoate

(P

rocla

im®)

Chlo

rfe

napyr

(Ale

rt®)

Spin

osad (

Success

®)

Em

am

ectin b

enzoate

Chlo

rfenapyr

Spin

osad

Em

am

ectin b

enzoate

Chlo

rfenapyr

Spin

osad

Strong correlation Weak correlation No correlation

Btk (Javelin®)

Methomyl (Lannate®)

Permethrin (Pounce®)

Bt 101

Potential for Cross-Resistance of Diamondback Moth

(Plutella xylostella) to Different Insecticides

Shelton et al., J. Econ. Entomol. 93:931-936 (2000).

CONCLUSIONS:

Some “new” insecticides may not

appear so new to the insect pest!

Threat of cross-resistance may already

be limiting the life of new insecticides.

The foundation of

Resistance Management

programs!

Little or no risk of nontarget effects

No risk of cross-resistance

Bt 101