It's an Internet rumor that is spreading like wildfire: Wi-Fi signals can make trees and other plants sick. Wi-Fi signals wirelessly connect computers and other devices to the Internet. The radio signals are similar to that employed by other, decades-old technologies such as television and cell phones, said Marvin Ziskin, a professor of radiology and medical physics at Temple. "Scientifically there's no evidence to support that these signals are a cause for concern."