Washington-area food prices rose 0.5 percent last month, a much smaller increase than the total 4.1 percent rise of the previous two months, following the end of the local supermarket price war.

Fresh and processed fruits and vegetables led the increase at 2.2 percent. Other increases were in candy, margarine and noncola carbonated drinks.

Prices declined locally on beef, cola drinks, eggs, pork and poultry. Nationally, food prices declined by 0.4 percent last month.

"Processed vegetables are going up nationally as well as locally because of seasonal smaller supplies and higher processing costs," said Floyd Rabil, a Labor Department economist. Meat prices are down because farmers generally slaughter large parts of their herds this time of year and demand is sluggish, Rabil said.

Another reason grocery prices leveled off was that the end of the supermarket price war that lasted through spring and part of summer brought about the return of the usual pricing policies--and a sharp increase in food costs--in August and September, Rabil said. Food prices rose 0.3 percent in July after dropping in each of the previous four months.

Before the price war began last spring, grocery store prices had risen 1.5 percent in December and January and one-half of one percent in February and March.

Giant introduced a "warehouse pricing" campaign in April and cut the prices of about 1,500 items, setting off what the company called a "wave of competitive price-cutting in the Washington and Baltimore markets."

Local supermarkets said they no longer could remain profitable with "warehouse prices" and began increasing prices in July to catch up with the rest of the nation.

The Labor Department said that during October, the cost of cereal and bakery products rose by 0.7 percent and the price of dairy products rose by 0.4 percent. Other food costs increased 1.2 percent.

The prices of meats, poultry, fish and eggs dropped by 0.9 percent.

The food price index stands at 282.0, which means groceries that cost $100 in 1967 now cost $282.