Ants and newly planted white pine


Hello. We just had a beautiful young eastern white pine professionally planted this past spring (150CM wire basket).

The tree has been watered and cared for. It does have a small aphid problem. I have been able to periodically hose these off and it doesn’t seem too terrible. I do notice the predatory ladybugs and wasps, as well as ants. I have read that this is normal (aphid predators are good) and that the ants shouldn’t damage the tree as they are there for the honeydew.

My question though concerns the ants. They seem to be emerging from the base of this young tree such that I wonder if they have made a nest under it. If this is the case is this it a problem? Can they damage the tree? Should I try to get rid of them and if yes, how?

(I wonder what kind of ant — they look like carpenter but again this tree is healthy and not what they would tunnel in. I wonder if the old root system of *very* large ash tree removed 2 years ago (stump ground etc) might instead make a desirable home for such ants? We planted the new pine close to where that old giant ask tree was?)

Any advice would be extremely welcome as we want this new tree to thrive in this location. Thanks.


Thank you for contacting the Toronto Master Gardeners about the new addition to your garden – a beautiful eastern white pine (Pinus strobus)! It sounds like your young tree is healthy and well-cared for. The presence of carpenter ants is an indicator of the presence of rotting wood. I think what is happening in your case is that these ants have built a nest in the remains (likely what’s left of the stump) of your previous ash tree. Carpenter ants do not eat wood. They chew rotting wood and discard the coarse sawdust as they make tunnels and establish their colony. Carpenter ants feed on living and dead insects, and honeydew. Thanks to the aphids on your new tree, the carpenter ants have a convenient source of food close to their home. I think the fewer aphids you have the fewer carpenter ants you will see on your young tree, so you should continue with the actions you are taking to control the aphids. As long as your tree remains healthy and strong, the carpenter ants will not harm it. It is very difficult to completely get rid of their nest, and controlling them is not necessary for the health of your tree.

Eastern white pine is a beautiful tree but many are stressed by less than optimal environment conditions. Plants that are stressed are more susceptible to insects and disease. Eastern white pine is very sensitive to city conditions including air pollution and road salt. Their ideal growing conditions include:

  • Enough space to accommodate their large size. These trees are fast growing and typically grow to 50-80’ in height, with a trunk diameter of 3-4’ and canopy width of 20-40’.
  • Full sun to part shade.
  • Well-drained sandy or sand/loam non-compacted (not clay) soil, although they will tolerate a fairly wide range of soils. If your soil is mostly clay, it would be good to amend it regularly with organic material like compost or well-rotted manure to improve the soil structure. Eastern white pine cannot tolerate moisture extremes.
  • Acidic soil, pH 5.5-6.5. A soil test done by a reputable lab can tell you what your soil pH is and will include instructions on what amendments and how much can be added to your soil to achieve the required pH level. You might also want to consider a fertilizer for acid-loving plants.

All the best with your lovely young tree!  Sept 20, 2023