New York - An innovative cockroach control strategy that keeps pesticide use to a minimum is much more effective than the standard approach -- regular, massive sprays of powerful bug-killers -- for wiping out the pests, a new study conducted in schools shows.

Exposure to cockroach allergens contributes to the development and worsening of asthma in children. Dr. Coby Schal of North Carolina State University in Raleigh and colleagues previously demonstrated that a strategy known as integrated pest management (IPM) works better than indiscriminate, regular spraying to control cockroach infestations and reduce levels of cockroach allergen in apartment buildings.

This was a major breakthrough, Schal noted in an interview, because efforts to control the insects have had disappointing results.

The IPM approach involves inspecting and monitoring cockroach populations, identifying "hot spots" of infestation, and applying pesticides as needed; the pesticides used are more specifically targeted to the insects and less likely to harm people compared to broad-spectrum pesticides used in standard pest management. For example, sticky traps may be placed inside cabinets, out of children's reach. Cockroach allergen is then removed from the area by vacuuming up dust and dead insects and their droppings and cleaning any other surfaces that may harbor the allergen.

In standard pest control, powerful pesticides are sprayed in certain areas -- for example, along baseboards -- in hopes that the insects will walk across the residue when they come out at night looking for food. But this method can expose people, especially young children, to pesticide as well.

In the current study, Schal and his team compared six schools in two different school districts that used conventional pest control methods and seven in a district using IPM.

They found that schools using IPM caught zero cockroaches in pre-set traps and they also had much lower concentrations of cockroach allergens.

While cockroach allergen was virtually undetectable in dust from the IPM schools, it averaged about 30 particles per gram of dust in the standard pest control schools. This is still fairly low, Schal said; dwellings with active cockroach infestations may have concentrations in the hundreds or even thousands of particles per gram, and a single cockroach can produce 1,500 units of allergen in a day.

In North Carolina, all schools must convert to IPM by 2011, while several other states have similar rules on the books, the investigators note.

Schal said he and his colleagues were pleased to see that the IPM schools were implementing the strategy very effectively, without any help from scientists or agricultural extension agents. "In the hands of the public sector, integrated pest management is actually working quite well."

While IPM is initially more costly than standard pest management techniques, he added, the expenses are well in line with school budgets.

SOURCE: Journal of Medical Entomology, May 2009