Not much bothers old fashioned junipers. They tolerate heat and frost, and anything else the weather throws at them. They do not appeal to many troublesome insects. Once established, they do not mind if they do not get much water. So, aside from over-watering and bad pruning, they are pretty indestructible. Yet, once in a while, otherwise healthy junipers die suddenly and mysteriously.
Sometimes, entire plants die. Sometimes, only big pieces of them die. The foliage is intact, but dried to a nice light brown. The roots are firm. In fact, the damage that caused such efficient death might not become apparent until the dead stems get dismantled and removed. It might even get overlooked because it is not the sort of damage that we expect to find in our tame home gardens.
Rats! They sneak in under the dense foliage to chew the bark from the main stems. The thicket of rigid stems protects them from cats and dogs. They can kill both shrubby and ground cover junipers, as well as ivy, ceanothus, cotoneaster, firethorn, . . . and nearly any sort of shrubby plant that they feel safe from predators in. They also eat vegetables and fruits, particularly citrus fruits.
The damage should be rather distinct. Bark is missing. Bare wood is exposed. Squirrels sometimes cause the same sort of damage, but usually on smaller stems in trees. Gophers do their dirty work underground by eating roots. If they kill junipers or other shrubbery, the dead plants can be pulled up from the soil relatively easily, and fresh gopher ‘volcanoes’ should be evident in the area.
Protecting stems and roots from rodents is more difficult than protecting developing fruit. The rodents know that they are concealed by the dense growth that they chew the bark or roots from, so fake owls are not much of a threat. Poisons are very unpleasant for the targeted rodents (duh!), and very dangerous to cats and dogs that might catch the poisoned rodents. Traps are effective and safe (except for the rodents . . . duh!) but take serious dedication to empty and reset!