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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.  

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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.

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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.  

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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”.

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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.

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Deer damage is a common problem in many parts of the country in the late summer and early fall.  Deer cause these “rubs” when they are removing the velvet from their antlers after they stop growing and when they are in rut.  During the rut they scrape the bark/cambium off the trunks of small trees as a visual signal and mark these spots with scent from glands on their heads.  The damage to trees can be extensive with many of the branches broken off and complete girdling of the trunk tissue. 

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. 

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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.

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Girdling roots are a significant problem that are typically caused by poor planting practices.  The top four pictures show girdling roots forming because of plastic edging being installed around the trees.  The biggest problem from these roots forming is the actual girdling of the tree’s stem or  buttressing roots which strangles them off and can lead to die-back and eventual death of the tree (pictures 5, 6, 7) or failure of a major structural root causing the tree to fall pictures 8,9).  The final picture shows how the fibrous roots of this tree have been greatly restricted to the area just around the trunk that would eventually cut into any structural roots that radiate outward.

The main cause of girdling roots is from container grown trees that are root-bound, edging or other constricting landscaping materials such as weed mat, or balled and burlap trees that haven’t have the root collar fully exposed and potential girding roots removed when planted.

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.  

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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.

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Good job, trees.

Emily Graslie (via emilygraslieoutofcontext)

And how about those arborists and urban foresters!

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These pictures show the amazing structure of an oak gall and the creature that causes them.  It appears to be a cynipid wasp (I didn’t have a chance to show it to an entomologist) though the small hole in the side of the gall seems to suggest that it could be a parasitic gall wasp that took over the gall from its original host.  The gall itself is plant tissue that the larval wasp has caused to grow this way.

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

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All of this damage to these trees has been caused by non-native eastern fox-squirrels (Sciurus niger).  Usually the scope and severity of the damage is not visible to people on the ground since they mostly chew the top side of the branches. 

Squirrels do this for a variety of reasons;  all rodents have constantly growing incisors that must be worn down by gnawing or they are feeding on the cambium or sweet sap that readily flows during the spring (bottom picture).  As seen in the top two pictures, the damage can be significant and the squirrels prevent the wounds from sealing over by continuing to gnaw on the wound-wood.

It is for this reason that it is good to discourage squirrels from inhabiting your trees.  One way is to reduce food sources such as feeders and fruit.  Also do not select trees like these maples (top and bottom are sugar maples (Acer saccharum) and Norway (Acer platanoides), which produce sweet sap/gum.  And additionally using physical squirrel barriers and pruning to prevent them from climbing the trees.

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.

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These trees ( top two pictures: yellowood-Cladrastis kentukea, bottom two:sugar maple-Acer saccharum)had branches removed over the winter that suddenly began to seep large amounts of liquid.

Trees weeping from cut or broken branches is common on warm spring days. This can be concerning to property owners who’s trees seem to spontaneously start gushing large amounts of fluid after winter storm damage or somebody having recently pruned them.

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

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These trees that have stubbornly held on to their dead leaves all winter (top to bottom: northern red oak-Quercus rubra, white oak-Quercus alba, American beech-Fagus grandifolia) are all displaying a phenomenon called marcescence. This means that the abscission layer at the petiole (which involves active cell growth) does not form until late winter or early spring.

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.

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Dwarf mistletoe (Arceuthobium spp.) is a common forest pest in the Western United States.

The variety that had caused the ���witches broom” [top two pictures] in this Douglas-fir (Pseudotsuga menziesii) and others that affect the Pine family can be a major problem in the forestry industry.

However, this parasitic plant is less of a problem in landscapes and urban trees due to plant spacing and diversity. The sticky seeds that are hydrostatically launched are unable to find an appropriate host. Also, if it is caught early it can be easily pruned out.

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].