Violent crime declined sharply in Prince George's County during the first half of 1982, according to statistics released yesterday. The drop is in line with recent declines in other Washington area suburbs and despite increasing unemployment caused by the recession.

There were 2,493 violent crimes through June this year as against 2,754 for the same period last year, a 9.5 percent decline. Violent crimes include murder, rape, armed robbery and assault. Overall crimes against property dropped 6.3 percent, although auto theft and nonresidential burglary rose 12 and 10 percent respectively.

County Executive Lawrence J. Hogan, who is seeking the Republican Senate nomination, credited increases in police manpower during his tenure for the drop in crime. The number of police officers has increased from 856 in July of 1978 to the current 892, a new high for the county.

Police union president Mal Curran, who has been sharply critical of Hogan, disputed the claims. "The additional manpower he's hired has not hit the streets. I don't think crime is down, it's up," Curran said. He said Hogan "is just doing what he has to do to get elected."

Police Chief John McHale said neighborhood watch programs are also a factor. "It's very encouraging. Crime has been down for 11 of the last 12 months. It shows me that citizens have gotten tired of crime and are banding together to stop it," he said.

McHale and Hogan also said the end of the baby boom generation is helping since most crimes are committed by people 15 to 30 years old.

"Up until now we have had a surplus of people in that age group," McHale said. "I think we're seeing the leading edge of this age drop."