Holly Tree

Q: We have a 30 foot holly tree that is probably more than 40 years old. We live in Lynn Valley in North Van. About 3 years ago it started losing leaves. At first the barren area was in the shape of a small bell from the bottom up about two feet. The barren area is now all the bottom and up to about six feet. I have talked to an arborist and various nurseries on the North Shore. With their advice I have raked the dead leaves away and fed a fertilizer (18-4-8) at the drip line but it keeps getting worse. The leaves that fall off or are soon to fall off curll up, some have black spots and most have sort of brown burn marks on their edges. The tree is at the end of a hemlock/cedar hedge so I realize it must compete for food. There is also another holly tree further up the hedge also suffering the same leaf losses. Is there a disease hitting the holly trees as I heard there are other hollies that someone working in the tree cutting business told me he had seen? Is there anything you could advise that I do? This is a beautiful tree that we don't want to lose it.
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A: It sounds like your Holly tree is definitely suffering from a disease or a bug. Holly Trees are prone to getting scale insects. These are insects that are secured to smaller branches and create this protective barrier over themselves. The best way to describe it is they look like little warts on the tree. They suck the nutrition and moisture that would otherwise go to the leaves causing the leaves to yellow and curl. The insecticide to control Scale insect is Malathion. The organic alternative is to spray the tree as well as applying a soil drench with Neem oil. There are also a number of fungus problems that can infect holly trees with very little means of control.

Based on scale being so prevalent on Holly I would suggest that you very closely examine the tree in May when scale becomes very active to see if they are the culprits, particularly as the tree is showing the results of scale infestations. One last tip. Make sure that the tree gets regular deep watering through the dryer part of summer.