AROUND THIS time every year, Maryland’s farmers spray pesticides on their lands to prepare for the growing season, and plenty of the stuff ends up in the Chesapeake Bay. But The Post’s Darryl Fears reports that scientists can’t gauge the effects of this on the marine environment with much certainty — could pesticides, perhaps, explain the bizarre appearance of intersex fish in the area? — in part because they don’t know how much of which chemicals farmers are spraying. A bill in Maryland’s General Assembly would change that.

The Environmental Protection Agency (EPA) rates pesticides based on the risks they pose to people and wildlife, and only certified applicators are allowed to use restricted-use chemicals, the most concerning type. But these regulations can’t prevent runoff — and a recent EPA report on toxic contaminants in the bay found that they did not in the case of pesticides such as atrazine, with uncertain effects on the life that depends on the Chesapeake’s waters, including the humans who drink from it.

So some Maryland lawmakers want to require those who spray restricted-use pesticides to report what they use and when to the state. Maryland law already obliges these farmers to keep records. All they would have to do is report their records to the state’s Agriculture Department. With access to the database, scientists would have a better sense of what chemicals to look for; they could better sort out which chemicals tend to flow into the bay at high rates and which stay on land; and they could construct geographically exact maps of chemical use and entry points into the water. That will help them tease out what’s disrupting the marine environment — not just intersex fish but also thin-shelled waterfowl eggs and tumor-ridden bottom feeders.

Naturally, though, farmers aren’t excited about a new rule. They complain that it will cost money to computerize their records and send them to Annapolis. They also worry that a centralized database with information on the use of only one class of agricultural chemicals — not others used in homes — will lead some to jump to conclusions about pesticides’ effects on the environment. The Maryland Department of Agriculture, meanwhile, seems uninterested in collecting the data.

But the EPA closely regulates the chemicals in question for a reason: They are the most dangerous. Therefore they are the first that scientists should study. If Maryland farmers are already putting in the effort to keep records, it’s hardly outrageous for state lawmakers to push its Agriculture Department to collect that information and then to provide it to scientists. It will then be on the scientists to use that information responsibly. Who knows: They might even find that pesticides aren’t to blame for some of the bay’s maladies.