The best control is raising the lawn soil's pH level. The best time to dethatch is in late spring. Don't do it during midsummer, when the lawn may be stressed, or when the lawn is wet. Hand raking is less harsh but can be impractical and back-breaking work for large lawns. Molasses diluted with hot water and sprayed on the lawn can help stimulate natural organisms to eat the thatch layer.
Aeration also helps.
Some catalogs sell aerating sandals with long spiked soles. Gardeners are meant to strap these scary-looking things to their feet and walk around on the lawn. Users claim, however, that they take far too much weight and leg strength to be effective. Get to work in the spring or whenever compacting and thatch seem to be a problem. Yankee Publishing Inc. All rights reserved.