This document discusses Bt rice, which has been genetically modified to produce Bacillus thuringiensis (Bt) toxins that target stem borers and leaf folders, major rice pests. Bt is a natural pesticide used in organic farming. The document explains that Bt rice reduces pesticide usage and costs while being safe for the environment, farmers, and non-target organisms. Studies in China found Bt cotton seeds cost similar to non-Bt seeds but required less pesticide. The document concludes by encouraging support of Bt rice to protect crops and reduce pesticide use.

1. What does Bt rice have to
do with me?
Christie BirkleandAndrea Arriaga

2. What is bt rice?
• Bt refers to Bacillus thuringiensis which
is a gram positive bacteria that lives in
the soil.
• Bt has a toxin (Cry toxin) that is used in
the fight against pests such as
caterpillars, moths and butterflies.
• Since it is a natural pesticide, scientists
decided to insert the gene that makes
the Cry toxin into the plant genome.

3. What pests does the Bt toxin protect against?
• Stem borers and leaf
folders (Chen et al.2006)
• Still have to spray for other
pests not effected by the
Cry toxin but spraying is
much less.
*The pictures show the life
cycle and damage leaf folders
and stem borers cause to rice
when not controlled. It is easy
to see if they are not
controlled, the whole harvest
can easily be consumed by
pests.
http://takingroots.in/ipm_rysb

4. It is already used as a pesticide?
• Yes… In the 1920s farmers recognized that the Bacillus thuringiensis
spores and proteins could be used against pests eating their crops.
• Today they are used as insecticidal liquid sprays that go by the names of
Dipel and Thuricide.
• Since they use Bt extracts, they are regarded as environmentally friendly
that have little or no effect on humans, wildlife and pollinators.
• They are safe (and allowed) for use on organic farms.

5. How to make the Bt rice plant…
http://www.ctu.edu

6. How is the Cry toxin effective?
• When bacteria spore due to unfavorable conditions as a survival tactic
they produce crystal proteins called Delta endotoxins that have
insecticidal properties against insects.
• When insects ingest the toxin crystals, the alkaline pH of their gut
interacts with the crystals making them soluble, allowing the protein to
become active in the gut.

7. What does the active protein do?
• Once the protein is
in its active form it
will be absorbed by
the cells lining the
gut and form a pore.
• This will cause the
cell to burst.
• When enough cells
burst, the insect will
die.
Formation of a pore results in the unregulated influx of
fluid, causing cell lysis.

8. What are the benefits of using Bt rice?
• Its already used as an organic pesticide.
• With the increasing resistance of pesticides,
genetically modified foods might be the only
option.
• Decreases pesticide use.
• It costs about the same to plant both Bt and non-
Bt rice.
• No harm to water living creatures that live in rice
fields.
• Its ecofriendly!

9. How much pesticides are really used?
The market price of Bt cotton seed was more than US$ 4.85/kg in 1999.
Because some farmers in the sample villages were contractors of Bt cotton
seed reproduction, and some farmers saved seed or exchange seed after Bt
cotton was adopted in the villages, on the average, farmers spent only US$
1.77/kg on Bt cotton seed and US$ 0.78/kg on non-Bt cotton seed.
-This graph represents pesticide
use in China, while the pesticide
use in the Philippines is less,
pesticide use for non-Bt varieties is
still high.
-The study by Huang and
colleagues also said that Bt
varieties seemed to promote the
reduction of pesticide use.
-Slow degrading pesticides also
remain on the plants longer and led
to poisonings when they were
eaten.
-Pesticide inhalation also causes
poisonings and long term health
problems.
*This study was a study on Bt
cotton in China in 1999 (Huang et
al. 2003).

10. How much do Bt seeds cost compared to non-Bt?
Bt Non-Bt
33B GK-12 GK-321 other
seed cost (US $) 66 44 69 69 63
pesticide used (kg/ha) 10.5 15 4.4 18.6 60.7
pesticide cost (US $) 30 41 16 40 178
fertilizer cost (US $) 1306 1089 2134 997 988
The table describes the total observations of
382 because some of the 282 households
planted more than one variety. The sample
distributions are 178 for SSB, 77 for GK-12, 42
for GK-321, 40 for other Bt, and 45 for non-Bt
(Huang et al. 2003).
It is interesting to note that while seed price is
the same and pesticide use is lower, the use
of fertilizer is a little more.
*Note: these are Bt cotton seed prices studied by
Huang and associates in 2003. The study says
that rice pesticide use is lower.

11. Eco-friendly how?
A study looking at the local rice fields showed that even the predators that ate the stem borers
and leaf folders were not affected by the Cry toxin (Chen et al. 2003).
There is no run off from spraying pesticides because the Cry toxin is inside the skin of the
plant.
The use of the Bt rice varieties also discouraged spraying later on in the year of pests that are
not effected by the Cry toxin such as spiders, mites and bollworm (Huang et al. 2003).
Since farmers are not mixing the highly toxic pesticide chemicals themselves the risk of
poisoning is much lower.

12. Protect non-stem
borers and leaf
folders by
supporting the
cultivation of Bt
rice and reduce
pesticide use.
Thank you for your
time and happy
planting!
References:
Huang, J.; Hu, R.; Pray, C.;
Qiao, F. and S. Rozelle.(2003)
Biotechnology as an
alternative to chemical
pesticides: a case study of Bt
cotton in China.Agricultural
Economics 29 :55–67.
Chen, M.; Ye, G-Y.; Liu, Z-C.; Fang, Q; Hu, C.; Peng, H-F. and A.M.
Shelton (2009). Analysis of Cry1ab toxin bioaccumulation in a
food chain of Bt rice, an herbivore and predator. Ecotoxicology
18: 230-238.