Pheromones - the trappings of sustainable pest control?

Sustainable control of the yellow stem borer, a pest that is threatening Bangladesh's rice crop and food security, may be possible through the use of pheromones and traps.

According to scientists from three organisations working in collaboration to find a sustainable control method, sleeve traps with a pheromone lure are both effective and cost-efficient in controlling the insect which is responsible for 70 to 80 per cent of pest damage to rice crops. The Natural Resources Institute (NRI), the Bangladesh Rice Research Institute and the multinational agrochemical company Syngenta are all involved in the project that is being funded by the Crop Protection Programme of the UK's Department for International Development (DFID).

credit: NRI, Sustainable Agriculture Group

Pheromones are used to lure the male stem borers into the trap where they eventually die thus preventing females from reproducing, explained J. C. Saha Choudhury of Syngenta-Bangladesh. "We trialed five different types of traps, but came to the conclusion that sleeve traps are the most appropriate for our country," he explained. The traps used in the trials are being imported from India but could easily be made locally when demand develops. "We have had a good response from the farmers. They were very interested because in one treatment we saw about 175 male moths caught in one trap," he said.

There are 10 major pests threatening rice production in Bangladesh, but the yellow stem borer (Scirpophaga incertulas) is the most damaging. Overall damage from pests and disease currently creates losses of 10 to 40 per cent of Bangladesh's rice yield.

With the current 130 million population set to increase to 160 million by 2010, alongside decreasing amounts of land available for rice production, the existing rice deficit can only get bigger said Mr Saha Choudhury. "By making crop protection measures you cannot increase the yield but you can save the damage," he explained.

And there are reasons other than food security to investigate alternative methods: "Economically this is a terribly important pest," said Dr Alan Cork from NRI. "Because the larva is actually inside the stem of the rice it is well protected from pesticides. So farmers in Bangladesh have to use fairly toxic granular pesticides to control the pest. These pesticides are becoming redundant because of the development of resistance to them, but more importantly because governments are becoming aware of the negative environmental and health aspects associated with the use of these compounds, so there is a now an urgent need for the development of alternative control technologies."

Disseminating the idea to farmers is already underway through local demonstrations, explained Dr Nazira Kamal, head of entomology at the Bangladesh Rice Research Institute. "We have some participating farmers and are working in their fields already to demonstrate how to use it," she said. It is also important that neighbouring farmers are prepared to work together if the technology is to work.

"If the farmers are illiterate they can still learn the benefits of using the lures around the traps through demonstrations. They know that the natural enemies [of stem borers] are saved, that the danger of insecticide use is avoided, their environment is safe and that they can have a good crop." And the money that farmers save in reducing their use of pesticides can be spent instead on herbicides which are less toxic and give a more effective return, says Mr Saha Choudhury.

Work continues to test the effectiveness of the pheromone lures over comparatively small areas. If individual or small groups of farmers can use the technology to protect their own crops, this would take care of the problem of encouraging large groups of farmers to collaborate in mass trapping. This is an interesting project, not only because of the technology involved but because it involves partners from both the public and the private sector. As Sarwar Ahmed, Managing Director of Syngenta-Bangladesh, points out: "If the objective is the same, then the collaboration can be very well coordinated. The public institutions want to bring in benign technologies for crop protection. We also want to do the same thing because, in the long run, it's in our interest that we look into the interests of farmers today."

For further information:
www.cpp.uk.com
www.syngenta.com
Email: syndhaka@bol-online.com