What does Bt rice have todo with me?Christie BirkleandAndrea Arriaga
What is bt rice?• Bt refers to Bacillus thuringiensis whichis a gram positive bacteria that lives inthe soil.• Bt has a toxin (Cry toxin) that is used inthe fight against pests such ascaterpillars, moths and butterflies.• Since it is a natural pesticide, scientistsdecided to insert the gene that makesthe Cry toxin into the plant genome.
What pests does the Bt toxin protect against?• Stem borers and leaffolders (Chen et al.2006)• Still have to spray for otherpests not effected by theCry toxin but spraying ismuch less.*The pictures show the lifecycle and damage leaf foldersand stem borers cause to ricewhen not controlled. It is easyto see if they are notcontrolled, the whole harvestcan easily be consumed bypests.http://takingroots.in/ipm_rysb
It is already used as a pesticide?• Yes… In the 1920s farmers recognized that the Bacillus thuringiensisspores and proteins could be used against pests eating their crops.• Today they are used as insecticidal liquid sprays that go by the names ofDipel and Thuricide.• Since they use Bt extracts, they are regarded as environmentally friendlythat have little or no effect on humans, wildlife and pollinators.• They are safe (and allowed) for use on organic farms.
How to make the Bt rice plant…http://www.ctu.edu
How is the Cry toxin effective?• When bacteria spore due to unfavorable conditions as a survival tacticthey produce crystal proteins called Delta endotoxins that haveinsecticidal properties against insects.• When insects ingest the toxin crystals, the alkaline pH of their gutinteracts with the crystals making them soluble, allowing the protein tobecome active in the gut.
What does the active protein do?• Once the protein isin its active form itwill be absorbed bythe cells lining thegut and form a pore.• This will cause thecell to burst.• When enough cellsburst, the insect willdie.Formation of a pore results in the unregulated influx offluid, causing cell lysis.
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 onlyoption.• 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 ricefields.• Its ecofriendly!
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 cottonseed reproduction, and some farmers saved seed or exchange seed after Btcotton 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 pesticideuse in China, while the pesticideuse in the Philippines is less,pesticide use for non-Bt varieties isstill high.-The study by Huang andcolleagues also said that Btvarieties seemed to promote thereduction of pesticide use.-Slow degrading pesticides alsoremain on the plants longer and ledto poisonings when they wereeaten.-Pesticide inhalation also causespoisonings and long term healthproblems.*This study was a study on Btcotton in China in 1999 (Huang etal. 2003).
How much do Bt seeds cost compared to non-Bt?Bt Non-Bt33B GK-12 GK-321 otherseed cost (US $) 66 44 69 69 63pesticide used (kg/ha) 10.5 15 4.4 18.6 60.7pesticide cost (US $) 30 41 16 40 178fertilizer cost (US $) 1306 1089 2134 997 988The table describes the total observations of382 because some of the 282 householdsplanted more than one variety. The sampledistributions are 178 for SSB, 77 for GK-12, 42for GK-321, 40 for other Bt, and 45 for non-Bt(Huang et al. 2003).It is interesting to note that while seed price isthe same and pesticide use is lower, the useof fertilizer is a little more.*Note: these are Bt cotton seed prices studied byHuang and associates in 2003. The study saysthat rice pesticide use is lower.
Eco-friendly how?A study looking at the local rice fields showed that even the predators that ate the stem borersand 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 theplant.The use of the Bt rice varieties also discouraged spraying later on in the year of pests that arenot 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 ofpoisoning is much lower.
Protect non-stemborers and leaffolders bysupporting thecultivation of Btrice and reducepesticide use.Thank you for yourtime and happyplanting!References:Huang, J.; Hu, R.; Pray, C.;Qiao, F. and S. Rozelle.(2003)Biotechnology as analternative to chemicalpesticides: a case study of Btcotton in China.AgriculturalEconomics 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 afood chain of Bt rice, an herbivore and predator. Ecotoxicology18: 230-238.