The strong invasion of tent caterpillars that has swept Orange County is not danger ous, according to, Robert W. Langlois, associate county agricultural agent. Most commercial fruit trees have been protected from these uninvited guests by spraying, he said. For private owners who may not have been ready for them, Mr. Langlois advises spraying with DDT. ‘‘Don’t burn them,' Mr. Langlois said, ‘It could harm the tree or start a fire. Or if you must burn them, cut them off firat and burn them in a protected place.'’ Most of the trees being attacked, he said, are wild apple and cherry. Record Photo by Edwin J. Safford. Don't burn them Ki