A Tactical War with Pests

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Win it to make your house allergen-free

On a pest control call, Ranjan Sapra did a recce of a bungalow in Delhi. The director of Pest Cure, a private pest control service provider, checked the manhole, the racks, old furniture pieces and the dustbin in the backyard leading out of the kitchen. He instructed his applicator, who quickly mixed insecticide malathion and water in the spray cylinder, masked face and began spraying.

But Neena Makan, owner of the house, asked him to limit the chemical to the exteriors, and use neem-based pesticides in the rooms and the kitchen. "In the past, the smell of insecticides left us with headache and nausea," she said. Using natural pest control techniques, such as herbal pesticide and traps, alongside chemicals is called integrated pest management (ipm). But what Sapra and Makan did not know was that the ipm would protect the family from allergens released by cockroaches that are often blamed for causing asthma.

After a six-month study, entomologists at North Carolina State University in the US concluded ipm is more effective in controlling cockroaches than conventional methods such as spraying insecticides.

Since ipm involves cleanliness and carefully looking for both live and dead cockroaches, it also leads to a long-term reduction in the allergens that persist in the dust after cockroaches are dead.

The entomologists studied allergens released by the German cockroach (Blattella germanica) native to American and European countries, which causes asthma among 43 per cent of Americans. According to a national health survey, 26 per cent Americans are sensitive to the allergens.

Since children are more susceptible, the entomologists studied public schools in North Carolina between November 2003 and May 2004. Six schools were using conventional pest management methods and seven, the ipm method. The researchers set cockroach traps to assess the level of infestation. They also collected dust samples from canteens, classrooms and other areas in the school to quantify the allergens.

The difference was significant, they said in the May issue of journal Medical Entomology. No cockroach was trapped in schools that followed the ipm method and the allergen concentration was 2.8 units per gramme of dust. In schools that sprayed insecticides, on an average 82 cockroaches were caught in each trap a week and the allergen concentration was about 18 times. The absence of allergens in other schools also confirms that cockroaches were not present in the surrounding and that it was not by chance that they were not trapped.

"ipm is effective in killing roaches," said Godfrey Nalyanya, lead author of the paper. In the ipm method, the ingredients are changed regularly. This delays the onset of resistance among roaches, Nalyanya added.

The study is relevant to India. Deepak Nama of the department of respiratory diseases, Fortis Hospital, Delhi, said, "Allergies caused by cockroaches are prevalent in India, but there is no data available."


Down To Earth, July 2009