Nebraska's 
Forest Health Report


Winter 2022
Sapsucker Damage
At a first glance, sapsucker damage can be mistaken for that of insects. A closer inspection reveals the holes occur in grid patterns or rough lines around the circumference of the tree.
Holes in the bark of a tree are usually a sign of insect attacks, left by beetles and moths as the adults emerge out of the tree. It is always important though, to note the shape of these holes as well as any apparent patterns that may be occurring. Insect exit holes will rarely have any sort of pattern relative to each other, and will extend some depth into the tree. If these holes seem relatively superficial and are occurring in a grid like pattern the culprit is likely to not be an insect, but a bird known as a sapsucker.

Sapsuckers are a species of woodpecker, and true to their name, prefer to feed on sap from holes they drill into trees. Nebraska has several species, though the most common is the yellow-bellied sapsucker. Most of the damage they do to trees will be done in the spring and fall during migration periods. Sapsucker damage is easy to spot due to its grid like appearance with holes being spaced out in grids or horizontal lines. These holes often do not penetrate very far into the tree as they are designed to induce sap flow for the bird to consume.
 
In Nebraska, damage is most often seen on pines, although it can be found on a number of other trees including maple. Heavy feeding can be a source of stress to the tree but is unlikely to kill it if it is otherwise healthy. Sapsuckers have also been noted to have favorite trees, so it is likely that they will return to the same tree year after year. While they can be a major burden it should be noted that they are a protected species and cannot be deterred in any way that would harm the bird. If you do find that your tree has been visited by one of these birds, make sure that the tree is receiving proper health care and try to catch a glimpse of this not-so-common woodpecker.
A yellow-bellied sapsucker adult. Credit: Johnny N. Dell, Bugwood.org
A Mild but Dry Winter
Unlike last year we have been spared (so far) from extreme low temperatures and early cold snaps. These temperature drops last year likely caused damage to outer branches of some trees as well as possibly setting off latent fungal infections already present in trees. Although temperatures this year have dropped somewhat, they have been nowhere near as low as last year. Of greater concern for this year is the lack of moisture in many parts of the state that has been ongoing for several months. Most of the state was in some form of drought headed into winter, and although it has abated somewhat, the situation is less than ideal.

Trees such as evergreens do not go fully dormant like deciduous trees do, which means they can still lose water during the winter. If trees have not been properly watered headed into winter they may experience winter desiccation. This is more common on small, recently planted trees but can occur on mature ones as well. The damage will usually present as browning and dieback on the windward side of the tree but may not be evident until the spring.

If you have a tree that experiences damage from winter conditions be sure to check the bud tips of the impacted branches. Live buds mean that the tree should recover fully in the spring, whereas dead buds indicate more extensive damage. Trees can recover from this even if damage is moderately severe provided that proper tree care such as adequate watering and mulching are employed.

Since we have had little to no snowfall this year, consider watering trees now and into spring. This will simulate snow melt that usually occurs in the spring.
The Return of the Bagworm
In the last few years, bagworms have become a major threat to windbreaks and ornamental evergreen trees. Local populations can quickly gain momentum and completely defoliate susceptible trees in a matter of weeks. Thankfully, after several bad years, last year showed very low numbers of this pest. This was mostly due to the extreme cold temperatures of nearly 30 below that were seen in February of 2021. Bagworms have a supercooling point of approximately 0 degrees F. This means that below these temperatures the insects will start dying. However, significant numbers often survive well below this point. Since our temperatures this year have not been nearly as cold we can expect to see slightly elevated levels of bagworms compared to last year, and it is likely that they will begin to increase more in the coming years. Homeowners should not get complacent with this pest and should continue to scout for young larvae when they emerge in late May/ early June. Early larvae will resemble small dunce caps on the foliage and usually appear around the time catalpa trees begin to bloom.
Degree Days
As we start a new year, growing degree days will once again be of importance as the weather starts to break and pests begin to emerge. Most of the state has seen little accumulation at this point, although it is slightly earlier than normal. Eastern tent caterpillars are one of the first tree pests to emerge as early as 90 GGD but usually closer to the mid 100s. Current forecasts suggest that southern Nebraska should expect them in about a month or perhaps sooner if warm temperatures persist.
Signs of Decay
Fungal conks (red) can be difficult to spot sometimes but often indicate a severe problem within the tree.
It isn’t always easy to tell when a tree is suffering from internal decay that may be a threat to it’s overall stability. Oftentimes, it can go unnoticed for years with the foliage appearing decent until major limb failure occurs. One exception to this however, is the presence of fungal conks on the trunk or branches.
 
Fungal conks are the fruiting bodies of decay fungi within the tree and can come in a variety of colors and sizes. Most often they appear as bracts or shelves on the tree and may be small or very large. Oftentimes when they are first noticed the tree will appear healthy otherwise, but their presence indicates that there is likely extensive decay within the tree. If you notice conks on your tree it is best to have a certified arborist make an assessment on the integrity of the tree and remove it if necessary. Unfortunately, fungi at this stage cannot be treated and are usually a result of other past health and stress issues in the tree. Proper tree care and pruning can go a long way in preventing this kind of situation.
Drought Monitor
Most of the state is now in some form of drought as dry conditions continue to persist. 
Drought conditions have been worsening throughout much of the state as most of it is now in a stage of moderate drought. Conditions have improved slightly in the panhandle since the Fall, but remain severe in many parts. Trees, especially evergreens, may need supplemental watering as temperatures continue to remain above average.
Mean Temperature
Temperatures held about normal to above average for much of the state during mid winter. It should be noted however that extreme fluctuations seen in February could damage parts of trees that broke dormancy. 
Most of the state has seen far below normal levels of precipitation this winter.
Compiled by David Olson, Forest Health Specialist
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