Early Spring Pests- The Spruce Spider Mite

Early spring is the perfect time to treat for a common ailment of a very common landscape tree.  The Spruce Spider Mite is just coming out of dormancy, ready to feed on whatever evergreen it can find.  Here’s what you should know:

What is it:

Figure 2: Webbing and excessive feeding damage on the terminal growth point of a spruce.  (Source: USDA)

Figure 2: Webbing and excessive feeding damage on the terminal growth point of a spruce.

(Source: USDA)

The Spruce Spider Mite (Oligonychus ununguis) is a nearly microscopic pest that is closer related to spiders than true insects.  This pest is a common feeder on most evergreens but is a major pest of both Arbor Vitae (Thuja occidentalis) and Colorado Blue Spruce (Picea pungens).  These pests are nearly always present at low levels as part of a healthy ecosystem, and a healthy plant can thrive regardless of light feeding.  However, unchecked their populations can quickly grow and cause significant damage to their host plant.  This damage is often made worse when the host plant is under stress caused by poor cultural and environmental conditions. 

The most common symptom is a stippled look to infested needles (Figure 1) caused by damage from their feeding.  Spider mites feed on the chlorophyll found in plant cells and leave behind a creamy white spot wherever they feed.  A single generation from egg to adult takes only 15-20 days, so this pest can rapidly outpace other beneficial insects keeping its’ population in check.  An excessive population will leave fine webbing wherever they feed (Figure 2) and can cause dulling and premature drop of the host plants’ needles.

Figure 1: Typical stippling damage from Spruce Spider Mites on Norway Spruce. Heavier infestations will cause significant dulling of the needles and premature needle-drop.  (Source: NJTE)

Figure 1: Typical stippling damage from Spruce Spider Mites on Norway Spruce. Heavier infestations will cause significant dulling of the needles and premature needle-drop.

(Source: NJTE)

When and Where to find it:

This pest is a cool-season mite meaning it is active during the spring and fall, but the warm temperatures of the summer push it to dormancy.  Look for activity to start in early April, as the Saucer Magnolia (Magnolia x soulangeana) comes into full bloom.  Most commonly this pest is found on Colorado Blue Spruce and Arbor Vitae but can also be found feeding on Norway Spruce (Picea abies) and If you’re having a hard time seeing the common symptoms, a simple “smear test” help identify their presence.  Hold a white piece of paper under the infested branch and shake the branch.  Any mites present on the branch will fall to the paper.  Next, smear your hand across the paper.  If there are green streaks (indicating feeding on the plant), you have spider mites.  If you have red streaks this is indicative of beneficial spider mites, who feed on the bad mites and keep their populations in check.  Beneficial spider mites tend to be larger, visible with the naked eye and are bright red in color.

How to Treat it:

On the average healthy tree, no intervention is necessary.  Light populations of spider mites do not significantly impede a trees’ ability to function normally.  If you do notice excessive feeding or webbing on the plant, it may be time to treat.  Several options are available, including miticide applications and horticultural oil sprays.  Timing for miticide application is tight and must be applied when feeding is active in April or September/October.  Horticultural oils control the dormant pests and therefore can be sprayed anytime during the spring or fall.  However, some evergreens are sensitive to oil sprays and may go off-color if misapplied.  Additionally, if you find beneficial mites on the host plant, you may want to hold off on treatment.  Any spray that treats for Spruce Spider Mite will also knockdown any beneficial mites present and can exacerbate the problem.  If you’re concerned about spider mite damage, it’s best to have you Nels Johnson Arborist decide which course of action is appropriate.


If you think you have spider mites, contact a Nels Johnson Arborist today for a free consultation.

The Importance of Being Kiln-Dried

 

When the temperatures start to drop and the snow begins to fall, our minds inevitably wander to the thought of a cozy fire in the fireplace (or fire pit!).  Before rushing to the store for your yearly supply of firewood, it’s important to consider the quality of the wood you’re purchasing.  Firewood quality can vary dramatically, and is highly dependent on the process through which it was dried.

A picture of our kiln used up at the North Yard. Firewood is loaded into large crates and dried for up to 2 days at high temperatures to ensure low moisture content.

A picture of our kiln used up at the North Yard. Firewood is loaded into large crates and dried for up to 2 days at high temperatures to ensure low moisture content.

When lumber is harvested from a felled tree, the wood is considered too “green” to burn. This wood does not burn well, if at all, and produces smoke because of its high moisture content. Wet firewood is difficult to burn in home burners, fireplaces, and firepits.  Prolonged use can adversely affect the performance of these heating systems. For effective combustion, firewood should have no more than 20 percent moisture content.  To achieve this through traditional drying methods, firewood must air-dry for at least one season. However, a superior process is to utilize a kiln to aid in the drying process.  A kiln is a thermally insulated chamber, a type of oven, that produces temperatures sufficient to complete the drying process. 


The Benefits of Nels Johnson Kiln-Dried Firewood

Kiln-dried firewood is the cleaner alternative to traditional firewood. Grocers, retailers and even brick-oven pizza shops prefer this method of dry, sterilized, firewood. Besides producing a measurably consistent product, kiln-dried firewood provides the following benefits:

Our services include delivery and stacking of clean, insect-free firewood.

Our services include delivery and stacking of clean, insect-free firewood.

  • Kiln-dried firewood can be burned the day you get it; it ignites easily and burns efficiently.

  • It can be safely stored indoors.  Kiln drying insures that insects, larvae, and mold are killed, making our firewood safe to store in your garage, porch, deck or living room.

  • Less flaking bark and debris (removed during the drying process) makes for tidier storage.

  • The wood produces a cleaner burn because it produces less creosote, which means fewer chimney issues, improved indoor air quality and less ash.

  • Kiln-dried wood provides a higher BTU (heat) output because energy is not being wasted to boil out excess moisture.

Our very own firewood specialist, Lisa Johnson, is responsible for overseeing the kiln-drying process at our North Yard. While the system is self-contained, it requires regular quality checks to ensure we consistently deliver a quality product with minimal moisture content.  If you’re interested in learning more about the process, or are interested in purchasing, you can contact Lisa at (847) 475-1877.  We can both deliver and stack your wood for you so you can spend more time enjoying the warm and enchanting fires this winter.

Dormant Pruning

A question that we arborists commonly hear is: “When is the best time to prune my trees?” I always chuckle at this because to me there is a lot to unpack from this seemingly simple inquiry. There is no hard and fast rule- depending on site conditions, species, and pruning goals (among other factors), the answer can vary wildly. Generally speaking, you can prune whenever you’d like; however, there are bad times and absolutely a best time to prune most plants. Usually that timing would be winter, and we refer to it as dormant pruning.

Dormant pruning refers to pruning a tree/shrub during its most inactive period, and for the Midwest, that is always the winter season. While most trees (with notable exception- I’m looking at you, oaks and elms!) can be pruned during the growing season, there are good reasons to prune during the dormant season.


You can readily see the structure of a tree in the winter when leaves aren’t filling out the canopy. This helps when making educated, minimal pruning cuts (and reduces the amount of work you have to do, too!). The strong convergent habit of this larch tree is easily visible.

You can readily see the structure of a tree in the winter when leaves aren’t filling out the canopy. This helps when making educated, minimal pruning cuts (and reduces the amount of work you have to do, too!). The strong convergent habit of this larch tree is easily visible.

1. During the winter, you can easily visualize the full structure of the tree. After fall leaf drop, there are no leaves to obscure the upper canopy of branches. This makes it much easier to decide pruning strategy (i.e. which limbs are being crowded) and to easily identify structural defects (like crossing branches, weak branch crotches, and dead/diseased limbs).

2. Contrary to common belief, dead/diseased branches are still easy to identify in the dormant season. While obvious signs of brown leaves may not highlight dead branches, an arborist can look for other cues such as sunken or shriveled branches, missing bark and saprophytic fungi. Leaves that died during the growing season, depending on the reason, also have a tendency to stay attached to the tree through the winter. It’s also easier to identify damage or defects that lead to branch death without leaves obscuring the view.

3. Pruning a tree often necessitates removal of live branches from the canopy. Removing these limbs during the growing season can lead to excessive resource removal. You lose both the limb AND the leaves when pruning just after the tree leafs out/pushes new growth. In the fall, trees pull the nutrient resources from their leaves to store in the root mass for the winter, hence the leaves turning color and dying. If we prune during the dormant period, we can avoid excessive loss of nutrients from the tree, and therefore reduce the amount of stress created when pruning. This is also why Arborists say that pruning in the spring- just after the tree used the stored resources to push new growth- should be done with caution.

Winter can be a great time to scout for diseases and defects on plants. This black knot, normally obscured by the leaves of the shrub, can be easily spotted during the off-season. In the winter, you can safely prune out this diseased wood without concern of it spreading.

Winter can be a great time to scout for diseases and defects on plants. This black knot, normally obscured by the leaves of the shrub, can be easily spotted during the off-season. In the winter, you can safely prune out this diseased wood without concern of it spreading.

4. Every pruning cut can be thought of as an intentional wound made to a tree. These wounds are openings for diseases (mostly rots) to enter the tree until they callus over. There are no diseases around in the winter to infect trees through new fresh cuts. However, wounds are also subject to extra exposure from the cold temperatures of winter. This is why some more sensitive trees are recommended for pruning in late winter, after the coldest months are in the past. A Nels Johnson arborist can help you determine which trees are more sensitive to winter damage.

5. Similar to the last point, there are several high concern diseases that are moved around (called vectored) by insects during the growing season. These insects are attracted to the sap of the trees they reproduce/feed on, mostly because wounded or stressed trees are easier to inhabit. When pruning cuts are made during the growing season, flowing sap will naturally be extruded from the wound. The two best known diseases that infect through this method are oak wilt and dutch elm disease. This is why it is important to only prune oak and elm trees during the dormant season, when the beetles are absent and sap flow is reduced. This preventative practice is so effective at slowing the spread of disease that some municipalities forbid the pruning of oaks and elms during the growing seasons. Any reputable tree care company in Chicago will not prune oak and elm trees between April 1st and November 1, with deadwood removal and risk mitigation being the exceptions. If you must prune an elm or an oak tree during the growing season, wound dressings are recommended to stop excessive sap flow.

Pruning trees in high traffic areas, or with special needs, can be very difficult during the growing season. These London Plane trees are located in the middle of an outdoor amphitheater, normally packing during warm weather. By pruning in the dormant season, time can be taken to properly pollard the canopies without having to jockey for workspace.

Pruning trees in high traffic areas, or with special needs, can be very difficult during the growing season. These London Plane trees are located in the middle of an outdoor amphitheater, normally packing during warm weather. By pruning in the dormant season, time can be taken to properly pollard the canopies without having to jockey for workspace.

6. An understated benefit for dormant pruning is that winter is when the rest of the landscape is also dormant. The ground is frozen, reducing any soil compaction from large machinery and concern about damaging annual and perennial plantings. Snow gives more flexibility of drop zones for large limbs, and cushions the plant material below. Loud machinery is less of a nuisance when families are bundled up inside staying warm. Additionally, there is less traffic in the landscape with routine mowing and landscape crews, reducing unintended run-ins and scheduling conflicts.


Dormant pruning provides many benefits over in-season pruning, including smaller factors not listed here. With some exceptions, winter pruning can be the best (and least stressful!) time to have your large trees pruned. If you’re interested in having your trees inspected, or are unsure if dormant pruning is right for your landscape, have a Nels Johnson Arborist schedule a site visit today! Give us a call at (847) 475-1877 to schedule an appointment now!