Bacillus thuringiensis (B.t.)

B.t. is a naturally occurring soil bacterium that causes disease on insect pests. It is accepted as an alternative in organic farming and is considered ideal for pest management because it is host specific and is non-toxic on natural enemies and on humans. B.t. is commercially available in most agricultural suppliers. It is sold in various formulations (spray, dust, and granule) and strains (Bt tenebrionis, Bt kurstaki, Bt israelensis, Bt aizawai, Bt san diego).

How it works?

An insect pest must ingest Bt before it is killed. When B.t. is ingested, it produces proteins that react with the cells of the stomach lining. These (proteins) poison and paralyze the insect's digestive system causing the insect to stop feeding within hours. A B.t.-infested insect will live for several days but will cause no further damage to the plant. It will die eventually from starvation.

How to use?

1. Spray thoroughly, covering all the plant surfaces.
2. Apply when larvae are less than 5 mm long or when the eggs begin to hatch. B.t. works best on young larvae.
3. In the hot tropics, it is more effective to spray B.t. in the late afternoon as there are longer and cooler hours ahead. This enables B.t. to remain longer on the leaves' surfaces. B.t. survives better in cooler temperature. Whereas, spraying in the morning provides a shorter and hotter environment.
4. Do not mix the B.t. concentrate with alkaline water (pH 8 or higher). Alkalinity reduces its effectiveness. To make the water acidic, add a few tsp of white vinegar in a gallon of water before adding B.t.

Pests controlled

1. Alfalfa caterpillar
2. Alfalfa webworm
3. Armyworm species
4. Cabbage looper
5. Cabbage webworm
6. Cabbage white butterfly
7. Colorado potato beetle
8. Corn borers
9. Cutworm
10. DBM
11. Grubs
12. Leaf beetles
13. Most caterpillars

Reminders

1. Buy the right B.t. strain for the insect pest you want to control.
2. Read the label and follow the instructions carefully .
3. Do not spray B.t. on wet days or when rain is expected.
4. Keep B.t. formulation in cool storage places.
5. Ask for advice from your local agriculturist office, when using B.t. for the first time.

External links

• UCSD. Bacillus thuringiencis. http://www.bt.ucsd.edu/index.html
• NPTN. Bacillus thuringiensis. http://npic.orst.edu/factsheets/BTgen.pdf
• EXTOXNET. Bacillus thuringiensis. http://extoxnet.orst.edu/pips/bacillus.htm
• Colorado State University Cooperative Extension. Bacillus thuringiensis. http://www.ext.colostate.edu/pubs/insect/05556.html
• Cornell University. Bacteria. http://www.nysaes.cornell.edu/ent/biocontrol/pathogens/bacteria.html
• The Ohio State University. Insect and mite management alternatives. http://ohioline.osu.edu/b504/b504_6.html

References

• Brooklyn Botanic Garden. (1999): Natural insect control: The ecological gardener's guide to foiling pests. Handbook # 139. Brooklyn Botanic Garden, Inc. Washington Avenue, Brooklyn, NY.
• Daxl, R.; von Kayserlingk, N.; Klien-Koch, C.; Link, R.; Waibel, H. (1994): Integrated pest management: Guidelines. Deutsche Gesellschaft fur Technische Zusammenarbeit. Eschborn,
• Gilberg, L. editor. (1993): Garden pests and diseases. Sunset books. Sunset Publishing Corporation, California.