A major pesticide company has agreed voluntarily to stop marketing a chemical shown to cause birth defects in laboratory animals and has promised the Environmental Protection Agency that it will not ask for repayment if the agency bans the chemical.

The action, which EPA officials called "quite unusual," was taken earlier this month, at the agency's suggestion, by Rohm & Haas Co., the nation's only manufacturer of the pesticide dinocap.

Dinocap, sold under the trade name Karathane, primarily is used to control fungus diseases and mites on apples. It also is used in lesser quantities on a variety of other commercially grown fruits, vegetables and floral crops, and is found in some pesticide sprays intended for use in home gardens and on house plants.

Although the chemical has been on the market about 30 years, the EPA only recently asked Rohm & Haas to test the chemical's ability to cause chronic diseases and genetic damage. One of those tests found that dinocap caused birth defects when fed to rabbits.

The EPA has asked for more tests to determine if skin contact with the chemical produces the same effect, a critical piece of information in determining whether the pesticide poses a risk to those who handle or apply it.

Rohm & Haas agreed to stop distributing the chemical until the agency has had a chance to examine the additional tests. The firm also promised to "caution its customers" against using dinocap products until April 1, when the EPA is expected to complete its evaluation.

The suspension is not expected to present much immediate hardship to major agricultural users. The pesticide typically is applied only at apple blossom time, late spring. That means it will be available in orchards next year unless the EPA decides a ban is warranted.