Home Depot and Lowe’s are being swamped by calls and e-mails from worried gardeners responding to unfounded rumors quickly spreading on the Internet that mulch made from house debris and fallen trees in New Orleans after Katrina contains highly aggressive Formosan termites.

“The rumors are false and very misleading,” said Karen Cobb, a Lowe’s spokeswoman in Mooresville, N.C. “But we can’t provide a rationalization to why people believe things that circulate electronically.”

Lowe’s and Home Depot said they only buy mulch from known sources, which follow industry association guidelines that prohibit the shipment of untreated bales containing termites. Neither gets mulch products from damaged areas of Louisiana, they said.