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SCIENCE-AUSTRALIA: Optimal Pesticide Use Can Save Cotton Farmers
By Neena Bhandari
MELBOURNE, Jun 7 (IPS) - A relatively low-tech approach to managing pesticides promises to help hundreds of thousands of cotton farmers across Asia raise yields and reduce environmental contamination.
Melbourne scientists are already collaborating with groups across Asia to combat the cotton bollworm (Helicoverpa armigera), an agricultural pest that causes five billion US dollars worth of crop damage each year and serious distress to farmers in countries like India.
Helicoverpa armigera is a major pest prevalent in 29 cotton producing
countries across Asia, Australia, Africa and Southern Europe. Besides
cotton, this moth attacks more than 100 different commercial crops including
maize, wheat, sorghum, sunflower, chickpea, lupins, soybeans, tobacco,
tomato, lettuce, sweet corn, capsicum and beans and flowers including
chrysanthemums, gladioli and roses.
Derek Russell and Philip Batterham, professors at the ‘Bio21 Institute' of the University of Melbourne have been working closely with Keshav Kranthi of the Central Institute of Cotton Research in Nagpur (India) and a number of other groups in India, China and Pakistan, to develop technologies to aid farmers in their fight against this destructive moth.
About 40 percent of the annual cost of growing cotton is spent on insecticides by the eight million cotton farmers spread across 11 states in India, while still failing to control the caterpillars. Cotton bollworm has often caused total crop loss driving hundreds of farmers in India to suicide.
Besides making the pest resistant, indiscriminate spraying of insecticides has created ecological havoc. Russell says, "By the mid 1990s, Indian cotton farmers were spending 43 percent of the variable costs of cotton production on insecticides, around 80 percent of that being for cotton bollworm control. Insecticide use on cotton was 50 percent of all
insecticide use in the country and it was increasing at seven percent per annum. For many, perhaps even most, cotton production was being rendered
uneconomic."
"In 1998-99, 14.6 percent of Indian cotton production was lost to insect -
mainly cotton bollworm - damage. The Green Revolution had increased the area
of more susceptible cotton bollworm hosts and the intensification of
cropping patterns meant that these hosts were available all year round." he
adds.
Kranthi and his collaborators, supported by Russell, have implemented a
control programme in thousands of Indian villages, slashing insecticide use by 50 percent, which has led to increase in yields by 11 percent and profitability by 75 percent. In the Wardha district of central Maharashtra, where the programme was introduced in 1997, common insecticides once again kill cotton bollworms easily.
According to official figures maintained by the provincial government of Maharashtra, close 1,500 farmers, most cotton growers, committed suicide in 2006 and the trend has continued this year in spite of attempts at intervention by the government.
Apart from higher yields, selective use of insecticides has major benefits for the environment and human health. A 2004 survey found that under the programme the number of farmers poisoned by insecticides had decreased roughly tenfold.
Russell says, "There were seven major groups of insecticides being used.
Now farmers are using four groups and rotating them intelligently, keeping
human and environmental health in mind." The strategy is implemented in an
integrated pest management context, not using insecticides that kill the
biological control agents or disrupting control of other pest species in the
cotton. The group has had some major successes, recently identifying
resistance genes for two important classes of insecticides, the
neonicotinoids and the spinosyns.
The collaborators have developed a number of test kits, similar to home
pregnancy test kits, which allow the farmer to determine if an insecticide
will be effective against the moth. It is now possible to test the quality or identity
of the insecticide, thereby allowing a farmer to check whether he is getting what he paid for. Another test detects whether a population of moth will be affected by a particular insecticide.
As farmers' spraying habits tend to be heavily influenced by their
neighbours, the scheme is introduced to whole villages at a time. The
programme tells farmers how to check whether insecticides are needed and if
so which type of insecticide to use and when best to use it, so that during
each of the four month-long "windows" of the growing season, only one type of
insecticide is used. The life cycle of the Helicoverpa armigera is about one
month, so the offspring of any resistant insects that survive one round of
insecticide are killed by a different one the next month.
Some aspects of the programme have been introduced in China and Pakistan. In Uganda, they have taken a different approach says Russell. "There is no effective agricultural extension support structure in Uganda, so, with donor and national collaborator support we have been running 9,000 demonstrations per year. By the end of 2007 we would have contacted every cotton grower in Uganda."
A similar test has been developed by Kranthi to check the integrity of
Bt cotton - a transgenic form of cotton that contains a bacterial
insecticide. Seeds can be ground up and a dip-stick style test used to
detect the presence of the toxin. Undoubtedly, Bt cotton has been a huge
success with widespread adoption in a number of countries including
Australia, China, India and the U.S, but public opposition to the genetic
modification of food crops means that in the short-term genetically modified
Bt plants are not a viable alternative for controlling the moth on the
majority of the crop species it attacks.
The next crucial step is to sequence the moth's genome, to find its Achilles
heel.
Prof. Philip Batterham from the Bio21 Institute wants to extend the kit technology by determining the full range of genes that can be involved in insecticide resistance. He says, "With this knowledge it will be possible to develop a diagnostic to predict the usefulness of different insecticides. We will be able to prescribe the best possible control treatment regime to control this pest."
"We believe it will be possible in the future to manage or prevent
resistance so that farmers can keep their produce in the market. To maximise
control over insect pests, we are working towards next generation
solutions - pest-specific insecticides," Batterham adds.
(END/2007)
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