I growing tips of all my tomatoes and the top foliage has become curled in on itself. Some leaves have rolled into a ball. Other than this they look perfectly healthy. I have read about the leaf hopper showing the virus when nibbling plants but the advice seems contradictory as to whether this would spread. Some sites say it will only spread to plants that are nibbled. Others say to destroy all plants at the first sign of it. Any ideas what I should do?