My winterberry plant has become infested with what appears to be web forming mite (?). Infestation was quick. The plant appeared normal just last week. I plan to remove the webs now because I don't want to leave them on the plant. Please advise on what they are and how I should treat the shrub. Should I prune it? I have two more winterberries next to the infested one - both look normal. What should I do to prevent infestation - thinking horticultural ?oil. Thanks very much.
We viewed your photos. This looks like fall webworm. This is a late season caterpillar that usually does not do a lot of damage. Here is more information on our website http://extension.umd.edu/hgic/fall-webworm-trees
We do not recommend control unless the shrubs are young and the infestation is heavy. There are predators and parasitoids that attack and kill fall webworm.
You can open the webbing with a pole pruner and expose the contents to birds. Larvae are or will be getting ready to pupate and no chemical control is recommended. Your shrub should be fine next season. Prune dead wood. Keep the shrub well watered during dry periods.