Common causes of dying conifers include dehydration, pests, chemical poisoning and diseases such as diplodia tip blight and phomopsis. Other conditions turn conifer needles brown or yellow but do not kill the trees. Periodic dropped needles and episodic color changes are also part of the normal conifer growth cycle.
Careful examination often reveals the cause of alarming symptoms and indicates the severity of the problem. The first step is to identify the tree species. This is essential information because it determines what is considered normal. Other important factors include the age of the tree and the season.
Many conifers shed their interior needles every autumn. This makes room for new growth and is a natural aspect of the conifer life cycle, but individuals unfamiliar with these trees frequently fear that the they are dying or seriously ill.
Color changes in exterior needles are abnormal and often symptomatic of diplodia tip blight, a fungal infection that manifests in springtime and kills new needles. Trees suffering from diplodia tip blight also develop tiny black dots on their branches. The most effective strategy for preventing this condition is to prune wounded and infected branches so the fungus does not incubate in the tree throughout the winter. Sterilizing pruning tools also prevents fungal transmission.