Black Gummy Coating on the Stems of my White Weeping Pine

(Question)

I have a small white pine that weeps over my pond that is infected with a black gummy substance along its stems. I first noticed it when I saw swarms of flies and ants on the stems that were feeding on it.
I treated it last fall with a copper sulphate solution which seems to have helped somewhat, but there is still some infection of new growth and it’s overall colour is poor/yellowish tone, not the healthy green it should be. I fertilized it and tried feeding with a tonic in the spring. I would hate to lose it to this gunk….any suggestions for me that will restore this beauty?
Thank You
Cheryl

(Answer)

The symptom of ‘black gummy substance’ on the stems of your eastern white weeping pine (Pinus strobus ‘pendula’) is a very general one that does not readily lend itself to a definite identifcation of the pest or disease that has been affecting your plant. Without a photograph or additional information, I am not able to offer a diagnosis, but here are some general suggestions.

First of all, if possible, remove all sections of the branches that are affected, cutting back into healthy wood. Before you begin pruning, thoroughly sterilize your pruners, and in addition, sterilize in between every cut, in order to avoid cross-contamination. Bag and throw away the infected branches as garbage. Keep an eye on the plant and keep it well hydrated in this warm weather.

A healthy tree is the best long term strategy for it to defend against pests and diseases. Therefore, correct culture is your best ally in keeping your tree stress-free and resilient. Eastern white pine prefers moist, well-drained, sandy loams that are acidic; it will decline gradually in clay, wet, or alkaline soils. If your soil is less than optimal, amend regularly with compost and acidify as needed. Avoid over-fertilization as eastern white pine has a strong affinity for soil mycorrhizae. Make sure it gets full sun, since white pine will become less shade tolerant as it matures.

Here is a link to the Tree Disease and Insect Guide for Conifers from Virginia Department of Forestry, which has a comprehensive list of the common pests and diseses that affect eastern white pine (third down the list).