25% setback on Bt cotton/Bt Corn More Susceptible to Aphids
2.Bt Corn Is More Susceptible to Aphids, Swiss Researchers Report
1.Pest attack: Punjab Bt cotton crop may be set back by 25%
By Padmaparna Ghosh
The Wall Street Journal, 31 August 2007
After a bumper cotton crop last year, this year has come has a shock to Punjab farmers, especially since 80% of the cotton acreage in Punjab falls under Bt crop
New Delhi: The cotton crop in Punjab, grown from the Bt cotton seed, has suffered a setback following attacks by a pest known as the mealy bug.
"According to the (Punjab) agriculture department, even though more area is under the cotton crop this year, production will be approximately 20-25% less," says a government official who did not wish to be identified.
After a bumper cotton crop last year, this year has come has a shock to Punjab farmers, especially since 80% of the cotton acreage in Punjab falls under Bt crop. Bt cotton seed is genetically modified to repel attacks by bollworms, a common cotton pest.
The districts of Mansa, Bhatinda, Muktsar and Ferozepur are the worst-hit by this pinhead sized insect, which feeds on plant sap. The last major attack of mealy bug was in 1978 with few and sporadic attacks since then.
Meanwhile, many of the farmers who didn’t plant Bt crop this year appear to be unaffected.
“The reason has nothing to do with Bt or non-Bt crop,” said A.K. Dhawan, cotton expert at the Punjab Agricultural University. “The reason is organic farmers (those who use indigenous seed varieties) practice multi-cropping. Mealy bugs don’t fly. They attack row after row of cotton crop. In multi-cropping, various vegetables and cereals are sown in rows next to each other so mealy bugs die when they hit another crop row.”
Some organic farmers are glad. “I have five acres and I sow maize, lobia, soybean, cotton and vegetables. Though my neighbour’s crop (also five acres) has been badly affected by the insect, my crop is intact,” says Amarjeet Sharma, an organic farmer.
Agricultural experts agree that when the focus is on controlling one pest, secondary pests can take over. “There have been numerous cases in China of such attacks on Bt cotton,” says Kavitha Kuruganti of the Centre for Sustainable Agriculture, a lobby group for organic farmers. “In Gujarat, the agriculture department has even set up a committee to look into the matter of attacks of mealy bugs and other pests on Bt cotton. The crop also requires high amounts of fertilizer inputs, which increases sugar content, thereby attracting sucking pests.”
Meanwhile, an association that represents seed sellers such as Monsanto-Mahyco Biotech Ltd, Rashi and Ankur notes that the problem is “not Bt related. Bt is only specific for bollworms. This has taken farmers by surprise. Not that they are not aware that they need to use pesticides with Bt cotton seed,” said R.K. Sinha, executive director, All India Crop Biotechnology Association, the umbrella organization for manufacturers of genetically modified seeds.
“It has been observed that when 100% of a region goes under Bt cultivation, it becomes susceptible to pests,” says a pesticide company official who did not wish to be identified. “The best example is Gujarat. We expected this to happen in Punjab too as more than 80% is under Bt and it did.”
This year’s attack will not only reduce cotton yield but it has pushed up input costs of farmers as well. “The cost to farmers has increased by Rs2,500 per acre on account of pesticides to contain the attack,” the pesticide official said. He added that because of this attack, his company had in the last few weeks sold additional pesticide worth Rs300 crore. Input costs for Bt cotton farmers is higher to begin with as each seed packet costs around Rs750. Moreover, Bt can be grown only in intensively irrigated areas as opposed to indigenous seeds, which are hardier. Irrigation pulls up input costs for farmers because they have to run pumps.
2.Bt Corn Is More Susceptible to Aphids, Swiss Researchers Report
Press Release -- Aug 29 2007
The environmental consequences of transgenic crops are the focus of numerous investigations, such as the one published in the journal PloS ONE, which was carried out by Cristina Faria and her colleagues, under the supervision of Ted Turlings, professor in chemical ecology at the University of NeuchÃ¢tel. The researchers observed that most transgenic maize lines were significantly more susceptible to the aphid Rhopalosiphum maidis than their conventional equivalents. "We have studied six lines of Bt maize containing an insecticidal gene derived from the bacteria Bacillus thuringiensis. The toxin produced by these genes is very specific and only affects the caterpillars feeding on the plants, not the aphids. Five of the lines contained up to twice the number of aphids", states Cristina Faria. She does, however, go on to clarify what seems, at a first glance, detrimental to the plant.
PAID ADVERTISEMENT "It all depends on the economic threshold for aphids in the region where maize is being grown. If these insects are not a major problem, then it is rather good news." In fact, aphids produce honeydew, a sugar-rich substance that can be used as a food source by beneficial insects, such as the parasitic wasp Cotesia marginiventris. This parasitoid helps the plant when it is attacked by caterpillars. It kills these pests by laying its eggs in them. In cages with aphid-infested Bt maize, Cotesia wasps lived almost twice as long and parasitized 37.5% more caterpillars. Hence, an increase in the number of aphids might help to control caterpillars in areas where these are a major problem. "However, in regions where aphids are considered to be a pest, growing Bt maize could be problematic," adds the biologist. Aphids mainly damage plants by transmitting viruses and using Bt maize might amplify this problem.
So where does this unexpected difference between conventional and Bt maize come from" The insertion of the Bt gene could have an effect on other genes, but the NCCR Plant Survival researchers rather think that by producing Bt toxin the plant's chemistry is otherwise altered. In Bt plants, they measured slightly higher concentrations of amino acids, which are essential nutrients for aphids. Moreover, the plant may mobilise energy resources for the production of the Bt toxin at the cost of producing substances that it normally uses in defence against aphids.
Disclaimer The following press release refers to an upcoming article in PLoS ONE. The release has been provided by the article authors and/or their institutions. Any opinions expressed in this are the personal views of the contributors, and do not necessarily represent the views or policies of PLoS. PLoS expressly disclaims any and all warranties and liability in connection with the information found in the release and article and your use of such information.
Citation: Faria CA, Wäckers FL, Pritchard J, Barrett DA, Turlings TC (2007) High Susceptibility of Bt Maize to Aphids Enhances the Performance of Parasitoids of Lepidopteran Pests. PLoS ONE 2(7): e600.doi:10.1371/journal.pone.0000600
PLEASE ADD THE LINK TO THE PUBLISHED ARTICLE IN ONLINE VERSIONS OF YOUR REPORT: http://www.plosone.org/doi/pone.0000600