A temporary restraining order obtained by local pesticide and lawn care companies has blocked new regulations in Montgomery and Prince George's counties requiring the posting of warning signs before pesticides are spread.

U.S. District Court Judge Herbert F. Murray, who issued the 10-day restraining order Friday night in Baltimore, scheduled a hearing on the case June 12.

The request for the order was made in a suit filed Friday by two industry groups, the Maryland Pest Control Association and the Maryland Alliance for Responsible Regulation of Pesticides. They asked that the county ordinances be set aside as unlawful, saying that a federal law preempts local regulation of pesticide use.

They cited an opinion to that effect issued in October by Maryland Attorney General Stephen H. Sachs before the Montgomery regulation was passed.

The Prince George's statute, which was passed last fall and was scheduled to go into effect today, requires the posting of warning signs 48 hours in advance of any application of a toxic chemical on lawns, golf courses or rights of way. The signs, which must specify what chemicals the pesticides contain, are to remain up for 48 hours after the application.

The Montgomery ordinance, passed in February and in effect since May 15, is similar but does not include the 48-hour advance notice provision. Violators in both counties are subject to maximum $50 fines.

Environmental groups contend that warnings need to be posted by lawn care companies because substances found in weed- and insect-killers may be carcinogenic or dangerous to children or pregnant women.

Officials in each county said they will seek to get the injunction dissolved.

Prince George's County Attorney Thomas P. Smith said it is the county's contention that the Sachs opinion does not apply to the Prince George's law.

"Our bill does not regulate pesticides at all," he said. "It does not prohibit any types of pesticides. It simply says that before applying pesticides, you must put up a sign telling people what pesticide you are putting on."

Bruce Bereano, an attorney and lobbyist representing the industry groups, said his clients do not oppose posting signs but would prefer a statewide law instead of local ordinances.

"It is very diffcult to be regulated differently in different counties, and there's no need for it," he said.

Bereano said the organizations were forced into filing the suit because lawmakers who supported the sign-posting laws were "unreasonable and not willing to negotiate" for a statewide bill.

This year, the pesticide industry lobbied for a bill in the Maryland House of Delegates that would have nullified the local ordinances. The groups also supported a bill that would have replaced the local laws with a weaker statewide law. Both bills were defeated.

Lawn care companies and pesticide manufacturers say that the chemicals they use are safe when applied professionally, and that having to follow different local ordinances would be confusing and time-consuming.

James Doyle, a lobbyist who represents ChemLawn, a large lawn service company, said the restraining order "puts everything on hold" until Murray can hear the industry's case.