Tree Care and Aboriculture

Maple cottony scale (Pulvinaria innumerabilis) found on this green ash (Fraxinus pensylvanica) is a pest that in sufficient numbers can cause significant stress to trees. It is a soft scale which is an insect in the “true bug” family of hemiptera that uses  piercing and sucking mouthparts to feed  on the fluids in the vascular tissues of the tree. The egg mass is the white cottony material that has formed underneath the female scale.  

Andricus quercuspetiolicola - Oak Petiole Gall Wasp These galls were found on a mature bur oak (Quercus macrocarpa) that was adjacent to the oak that had what appeared to be ‘oak flake gall’.  As with oak flake gall, it presents little harm to this this tree though it could be responsible for the die back on this leaf.

At first glance, the underside of these leaves on this bur oak (Quercus macrocarpa) look to have some sort scale (Hemiptera). However they are actually a kind of gall, likely ‘oak flake gall’, which is formed by a gall wasp (Hymenoptera).  Like most galls, they are an aesthetic issue and do little harm to the tree.  

European fruit lecanium (Parthenolecanium corni)  Empty husks left over from the scale found on a sugar maple (Acer saccharum).  Most of the internodes from the previous year’s growth had scale present. Even though the dessicated husk is quite hard this species belongs to the group known as the “soft scales”.

These pictures were taken as a reminder to check credentials and that there are many landscape “professionals” that don’t know how to correctly prune trees (and possibly don’t care)  In these cases people have probably paid a good amount of money and had nothing done but have their property permanently damaged and in some cases significantly.  The first four pictures show the horrible practice of topping with the second tree having the obsolete painting of the cuts.  The next four were at the same business which I hope didn’t pay someone for the damage that was to all of their trees: massive stubs, nicks from the chainsaw, flush-cuts, torn bark and seemingly random removal of branches.   The last two show another business whose trees had large stubs left and “lion’s tailed” branches on all of their trees.

Bark tracing is an effective way to help the trees seal off the wound by removing the ragged edges and dead/dying tissues. With a sharp box knife (or chainsaw for larger thicker barked trees with other types of damage) cut through the bark and cambium around the wound down to the wood, being careful not to peel it off the trunk more.  Creating clean edges and smooth rounded perimeter, encourages effective sealing callus tissue and woundwood. 

This American linden's (Tilia Americana) top failed due to a large cavity that was most likely created by a red-shafted northern flicker (Colaptes auratus cafer). Urban trees can create habitat for a large variety of wildlife, some of which cause significant damage that can lead to failure. This is another reason to have trees that are in proximity to structures and other high-value targets regularly inspected by a competent arborist.

The best way to mitigate this problem at planting is to fully expose the root collar and pull away all all bisecting roots from the stem. With heavily root-bound container grown trees use a knife or shovel to carefully  score and tease away the roots from the stem and break root ball or by completely washing away the soil from the root ball and structurally pruning and teasing out the roots prior to planting.   If edging is to be used, make sure it is at least to the drip-line of the tree and never use landscape fabric around trees.  

Theses large larvae were found in a large, decayed cavity in a limb of a Norway maple (Acer platanoides) last summer. After several months living in a special beetle medium in (second picture) they pupated into adults (third and fourth pictures). The fourth picture shows the ball of soil they form around them while pupating. They were identified as hermit beetles (Osmoderma subplanata) which are in the scarab beetle family. Hermit beetles are very uncommon in this part of Montana likely because this genus of beetle requires large, mature oaks, or maples with decadent cavities for its larvae. The urban forest provides an oasis that fulfills this need in this part of the country which is mostly conifer forest.

These galls cause little harm to the tree and many of these wasps are beneficial species that feed on parasites that harm the tree.

An exception, in this part of the country, would be tolerating a small amount of damage to you trees in order to provide habitat for native squirrel species which have a much smaller impact.

This phenomenon represents very little risk to the health of the tree beyond the damage to the branch.

This trait is strongly genetically controlled and is common in the Fagaceae family. However, non- marcescent deciduous trees will hang on to their leaves if the tree, branch or leaf dies before autumn and before an abscission layer can form.

The actual dwarf mistletoe plant can be seen growing out of a Douglas-fir stem and cambium [second and third from top] as well as what the plant itself looks like next to the needles of the tree [bottom].