In order to reduce the number of rodents in the city, the Cambridge City Council has decided to change its rules about garbage collection and storage.

After April 3, residents will not be allowed to leave plastic garbage bags outside overnight for morning collection. According to notifications received by Cambridge residents over the weekend, plastic garbage bags will be allowed on the streets in the morning, but only before the 7 a.m. collection time.

Cantabrigians who want to put their trash out the night before collection day will have to do so in garbage containers with tight-fitting lockable lids. Even in these containers, the trash will only be allowed out on the streets after 6 p.m. the night before collection.

Every Cambridge resident received a postcard in the mail detailing the new regulations and including a coupon for a $12 sealable trash can, redeemable at five of Cambridge’s hardware stores.

“Eliminating plastic bags overnight—that will really make a difference in terms of controlling rodents,” said Commissioner of the Department of Public Works Lisa Peterson.

However, City councillor Henrietta Davis said that although focusing on trash collection day is a start, the new regulations do not tackle all the trash issues.

“Trash collection only covers twelve hours but the other six and a half days of the week are the real problem,” since people may store trash in their yards on those days, Davis said.

Keeping trash in yards is against state sanitary codes.

Residents who violate the new overnight-garbage rules will be fined $25 for every day unauthorized garbage is left on the streets.

In an Oct. 2005 proposal to City Manager Robert W. Healy, the council requested that he “consider significantly increasing fines for garbage that is put out at the wrong time or in improper containers.”

The city had attempted to address the rat problem in a proposal last September requiring that rat traps be set out and rat holes sealed.

Last December, Healy proposed tackling the rodent problem by focusing on regulating trash collection rules.

“One theory of the City’s rat infestation problem is that there are more rats because of a good food supply and, in order to reduce the epidemic, the food supply needs to be reduced,” an Oct. 17 resolution said.

In November, the City Council’s Ordinance Committee held a public hearing on the rat problem.

At the hearing, a Cambridge resident, Wanda Queen, said “she caught five rats in her home in one day,” according to the hearing minutes.

Economy Hardware and Home Center on Mass. Ave., which agreed to sell sealed containers for a reduced price of $12 each, has seen a spike in sales during the past week since the city council sent out the coupons, according to store manager Heidi Kiwel.

The general manager of Tags Ace Hardware on 29 White St., Peter Albrecht, said that his store decided to participate in the coupon program because it wanted “to help the town out.”

Harvard has also attempted to address rat infestation for the past three years, according to Rob Gogan, waste manager at Facilities Maintenance Operations.

But the University has been working on prevention by trying to dispose of food separately from non-edible trash, reducing the amount of food in the waste.

“The main reasons neighborhoods have rats is because there is food,” Gogan said. “People don’t eat all their food.”

Custodians and yard garbage collectors will see a rat every two or three months, according to Gogan.

They “learn to go around and kick the barrels before they dump them” to scare away rats, he said.

—Staff writer Shifra B. Mincer can be reached at smincer@fas.harvard.edu.