As any parent knows, poor midterm grades present a dilemma. Is it better to be encouraging and positive, or to get outraged and impose punishment? Lean too far one way and you're a softie, the other and you may face only resistance and obstinacy.

Such is the case with the two-year milestones set last year toward the cleanup of the Chesapeake Bay by the states whose rivers drain into the estuary and the U.S. Environmental Protection Agency. At the midway point, the results are a mixed bag at best. In some categories, the performance is disturbingly low.

Environmental activists sounded some alarm as Gov. Martin O'Malley and officials from Virginia, Pennsylvania and other states met in Baltimore on Thursday and declared their performance to be good and generally on track. While that's true by some measures, it isn't by most.

In Maryland, for instance, the amount of farmland where cover crops have been planted to reduce soil erosion and runoff is less than one-fifth of what it should be. Virginia has fallen woefully short of its target for erecting fences to keep cattle and other livestock out of freshwater streams. Not nearly enough farmers in Pennsylvania have adopted nutrient management plans to keep manure and fertilizer from pouring into the Susquehanna River and its tributaries.

Advocates estimate that states are probably going to meet no more than one-third to one-half of pollution-reduction goals next year. That already has the environmentalists thinking about sanctions and whether the EPA shouldn't be reading them the riot act right now — spelling out the specific consequences of failure in the form of tighter federal regulations and/or the loss of federal funds.

That's something the governors don't want to hear, particularly in an election year. And they have a ready excuse: Tight state budgets and the possibility of further job losses in a fragile economy have caused them to regulate with caution.

Certainly, there's some truth to that. Maryland's voluntary cover crop program lacks sufficient funding to give farmers an adequate incentive to put land out of production. The state could mandate fall cover crops instead (or at least ban fall fertilizer applications), but farmers say now is not the time to raise their costs.

But that kind of logic overlooks the considerable benefits of the Chesapeake Bay to the region's economy, not just in seafood production but in tourism and land value. Just ask residents of the gulf states about what happens when a region's greatest natural resource becomes overwhelmed by pollution. An oil spill merely accomplishes more quickly what the relentless tide of nitrogen and phosphorus is gradually doing to the health of the Chesapeake Bay.

Farmers are not the only ones to blame. States have done just as poorly at retrofitting towns, cities and other developed areas to reduce polluting storm-water runoff. But developers and the real estate industry are just as likely to cry foul to state and local governments when regulations are tightened or fees are raised.

Now is not the time for direct EPA intervention; it's simply too early in a process that began in 2009. But if two-year milestones are not met in 2011, it will be occasion for something more than stern conversation. The region's governors may be proud of what has been accomplished (and the latest technological doodads, such as a website to help track the cleanup's progress), but tough decisions need to be made involving a broad spectrum of polluters, from the failing backyard septic tanks to poultry farms.

With the Gulf oil mess unlikely to end in a happy result, President Barack Obama may well be looking for an opportunity to restore public confidence in his administration's stewardship of the nation's waters. The Chesapeake Bay could prove a shining example of what a firm federal hand can do to force errant parties with failing grades into action.