A student helps himself to a meal at Cabot House yesterday. This spring fruit flies have infested the Cabot dining hall, taking advantage of what Harvard’s pest-control office says was a “compost-like situation.”

A fruit fly infestation that became noticeable in Cabot House after Spring Break has been traced to the existence of “a compost-like situation” in abandoned dumbwaiter shafts and trap doors in the dining hall, Harvard officials said yesterday.

The problem originated in a closed-off area under the conveyor belt that transports students’ trays back into the kitchen, said Gary D. Alpert, Harvard’s chief pest-control official.

“There was an old drain where food has been collecting long enough to cause fruit flies to breed,” Alpert said.

The team of workers working to repair the infested area “are going to clean old food that was not washed out and has collected in the area,” he said. That old food has been creating the “compost” environment for flies to breed.

Alpert, an entomologist with Harvard’s Office of Environmental Health and Safety, said he has discovered two abandoned shafts but that there may be more.

Alpert said he was confident the fruit flies are a result of the environment under the conveyor belt and are not due to anything in the food preparation itself.

Cabot House resident David J. Zimmer ’04 said he thought the delay in finding the cause was “disturbing.”

“It’s the sort of thing that you would hope would have been noticed quicker since the fruit flies have been around for a while,” he said.

Alexandra McNitt, director for marketing and communications at Harvard University Dining Services (HUDS), said fruit flies are not unusual at this time of year.

Alpert and other specialists from the Department of Environmental Health and Safety have been working with HUDS to determine whether the fruit flies present a health risk, McNitt said.

She said they have concluded that the fruit flies are “pesky, but no health risk.”

Though the fruit flies may not be physically harmful, Cabot House Master James H. Ware said he has called on students to take “collective responsibility” for some of the behavior in the dining hall that may lead to fruit flies.

Ware said students should be responsibile for disposing of their food during hours when there are no HUDS staff in the dining hall. Cabot’s dining hall is open 24 hours a day.

The fruit fly infestation compounded the recent bad luck of Cabot House residents, who also came back from Spring Break to find that the dining hall’s main dishwasher was broken—forcing residents to eat off paper plates for a few days.

While most students were annoyed—and Ware said he was too—some students found the paper plates bearable.

Milton E. Otto ’03 likened the experience to “having a picnic every day.”

McNitt said HUDS repaired the dishwasher instead of replacing it in light of the fact that all Quad dining halls will undergo major renovations this summer.