NORFOLK (AP) — States in the Chesapeake Bay Watershed have collectively fallen behind in implementing a plan to reduce nitrogen pollution in the country's largest estuary, the Environmental Protection Agency said Friday.

Pennsylvania was mostly to blame in part because not all of its farms are using the best practices to prevent nitrogen runoff, which often comes from animal waste, according to EPA reports.

Excess levels of nitrogen in the bay can stimulate the overgrowth of algae, creating so-called "dead zones" that have too little oxygen to support wildlife. The EPA wants states in the watershed to implement 100 percent of a long-term pollution-reduction plan by 2025.

When it comes to nitrogen pollution, the agency said its goal of having 60 percent of the plan in place by 2017 will not be met. Instead, only about 46 percent of those strategies will have been employed.

Besides Pennsylvania, the states in the Chesapeake's watershed are Delaware, Maryland, New York, Virginia and West Virginia as well as the District of Columbia. The EPA's long-term plan also focuses on pollution from sediment and phosphorous, for which the states and the District will be on track to addressing in 2017.

Neil Shader, press secretary for the Pennsylvania Department of Environmental Protection, acknowledged in an email that "significant work remains" when it comes to addressing nitrogen. But he said Pennsylvania has made strides to address pollution in the watershed after "years of inaction by state leaders."

He said Pennsylvania is "committed to making progress toward 2025 goals for all pollutants."

In the wake of the EPA's report, U.S. Senator Ben Cardin of Maryland praised his state's progress toward reducing nitrogen and phosphorus emissions from sewage plants.

"We have reached our target for nitrogen emissions from the wastewater sector much earlier than expected," said Cardin, a Democrat.

Rebecca LePrell, Virginia executive director for the Chesapeake Bay Foundation, also noted progress in her state but said it "cannot slow down its efforts."

"In fact, our biggest challenge lies ahead when it comes to reducing polluted runoff from cities and suburbs," she said in a statement. "The importance of strong state funding, regulatory oversight, and local leadership cannot be ignored."

___

This story has been corrected to show that states in watershed won't to meet the goal of implementing 60 percent of pollution-reduction plan by 2017, not a goal of reducing nitrogen levels by 60 percent.