WASHINGTON (AP) _ Agriculture Department researchers think they have found a solution to the pesky problem of cockroaches: a gout medicine called allopurinol that wipes out entire roach populations in four to six weeks.

Agricultural Research Service entomologists say the medication prevents the manufacture of uric acid in both humans and roaches. In humans, the acid contributes to the painful joint condition. In roaches, it is needed by inseminated females to develop embryos.

''Without the crucial uric acid, females simply can't reproduce,'' said Daniel R. Suiter, who works at the ARS Medical and Veterinary Entomology Laboratory in Gainesville, Fla.

He and colleagues have conducted tests on thousands of German cockroaches, ''the type city dwellers know so well,'' according to a USDA announcement of their findings. The cockroaches were fed plain rat chow and chow laced with the drug. In four to six weeks, the population feeding on the treated rat chow died off, Suiter said.

ARS and the University of Florida share a patent on the new use for allopurinol. Several companies have expressed interest in developing a commercial cockroach exterminator using their technology.

The drug has been used safely by people for over 30 years, so a company interested in marketing it as a cockroach control can rely on the toxicological studies that have already been conducted, the announcement said.

''When you're looking at the development of a new compound, one of the biggest costs is toxicological data,'' Suiter said.

But additional studies proving environmental safety may be needed for Environmental Protection Agency approval for the new use of allopurinol, he said.

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WASHINGTON (AP) - The Agriculture Department is removing some parts of Florida from the list of citrus canker survey areas.

Regular inspections for citrus canker will no longer be required of trees, plants and groves producing regulated fruit in the areas removed from the list, the department announced this month.

Florida is the only state where citrus canker currently exists. To prevent the disease from spreading, certain areas have been placed under quarantine, and regulated articles are subject to interstate movement restrictions.

Survey areas are outside the quarantine areas and serve as containment or buffer zones.

Removed from the survey areas are parts of Hillsborough and Manatee counties and all of Sarasota County.

''We are pleased that no infestations have been found in these areas since they were placed under observation,'' said B. Glen Lee, deputy administrator for plant protection and quarantine with the Animal and Plant Health Inspection Service.

''There has been a significant reduction in new citrus canker outbreaks in recent years,'' he said. No citrus canker has been detected in Florida since January.