May Tree Care | 7 Topics for Tree Health | OMAHA, NE
Spring is in full swing! There is a lot to do and a short time to do it. If you live with trees in Nebraska, this article is for you! The decisions you make this month will set your trees up for success during the growing season. This month we cover bagworms, emerald ash borer, scale, chlorosis, and pruning (of course!).
Prune Deciduous Trees
Now it is time to prune all deciduous trees, except those susceptible to certain pests & diseases (See our March & April articles for a list of trees you should prune before bud break). Once leaves are on, trees grow rapidly. Rapid growth means rapid healing. If you prune early in May, you can take full advantage of this. Trees will recover faster and be more resilient to the extreme heat of summer and cold of winter.
Structural Pruning: Prune Baby Trees, too!
Urban trees are not in a normal situation. In a forest, there is competition, and they have to reach for sunlight, which causes them to grow upright. When trees stand alone, the sun is all around, and the branches can grow horizontally & cross each other. These growth habits can lead to potential health & safety issues in the future.
In the long run, trees do better if you can help them along, giving structure through proper pruning techniques. Pruning should start early. Give them at least one year after transplanting to settle in and establish a root system. You can make exceptions to the 1-year rule if something significant is wrong, like broken or crossing limbs. You can remove up to 1/3 of the branches at a time. Pruning wounds may heal entirely if pruning occurs while the tree is young.
Prepare for Bagworm Hatch
As the temperature heats up, so does pest & disease activity. In May, Nebraska bagworms prepare to hatch as eggs have already been laid. Bagworms can affect many kinds of trees, but they decimate evergreens. You may find them on maple, sycamore, box elder, etc., but they rarely cause premature death for deciduous trees.
Once hatched, the bagworm larvae seek out a host and construct small bags made of silk and bits of plant material. During the larval stage, bagworms emerge from their bags to feed on leaves, needles, and other plant parts, sometimes causing significant damage or complete defoliation. As they mature, they pupate within their bags and eventually the males emerge as winged adults. The adult males typically fly around in search of mates, while the flightless females remain in their bags to lay eggs.
With changing weather patterns, bagworms in Nebraska can sometimes get two hatchings within one growing season! Inspect your trees regularly during the growing season. Manage infestations through a combination of mechanical and chemical control methods:
OPTION 1: Mechanical Method
You can pick the bagworms in May before they hatch in mid-June. Being proactive can save you time & money. It is also more environmentally friendly than insecticides.
OPTION 2: Chemical Methods
If you missed the boat on the mechanical method, or the problem persists despite interventions, you may consider insecticide treatments. Aim to treat in mid-June, when females are actively feeding.
Check for Scale Crawlers
Scale refers to a group of small insects that feed on the sap of trees and shrubs. They attach themselves to the tree's bark and can cause damage to the plant if left untreated. You can identify scale insects by their protective covering, resembling small, round bumps or scales.
May is a great time to check for scale crawler activity. If you used a horticultural oil over the winter but see activity now, your horticultural oil was ineffective, and you may need to consider a spray insecticide. It's important to regularly inspect trees and shrubs for signs of scale infestations to prevent further damage & monitor the efficacy of treatment.
Treat Chlorosis (Yellowing Leaves)
Treat for chlorosis after leaves have fully emerged. Chlorosis is often caused by iron deficiency in lime-rich soils. Omaha sits on limestone bedrock which causes many areas to be lime-rich and sets the foundation for problems to arise. The problem can compound when certain kinds of trees more prone to chlorosis are planted. Trees commonly affected by chlorosis include pin oaks, river birch, magnolias, red maples, white pines & more (in that order).
How can you tell if your tree has chlorosis? Look for pale or yellowing leaves and/or needles.
Chlorosis can present itself as yellowing of the entire or partial canopy. If you noticed yellowing leaves last year (outside of the normal fall activity), or if you observe in the leaves this spring, your tree may need an iron injection. Timing for injection is imperative as it is best done before daytime temperatures reach 90 degrees.
Treat for Chlorosis in May to ensure that your trees are in optimal condition and for continued good health. Homeowners tend to notice chlorosis later in the season when it's hot, and they are outside more often. At that point, the trees are already feeling fatigued, and the problem should have already been addressed. Continued monitoring and maintenance will ensure trees in your yard are happy for the growing season and ready to weather upcoming storms.
If your tree had it last year, treat it. If you see it on this year's leaves, treat for it at optimal times: spring or fall. If you aren't sure, ask an arborist.
Prepare for Emerald Ash Borer
Emerald Ash Borer (EAB) is here in Omaha. If you have an Ash tree, you must get on a preventative treatment schedule or plan to remove the tree. A qualified Nebraska Arborist can tell you if your tree qualifies for EAB injections. Our in-house arborists offer complementary Emerald Ash Borer consultations (Also quotes for tree removal in Omaha & surrounding areas, if needed).
If your ASH tree is not currently on a treatment schedule, and you would rather not lose the tree, you need to act fast to get on the calendar for this treatment season. Ideally, you would have wanted the assessment done by April. You may still be able to get in under the wire if your favorite Omaha tree service has openings. The treatment window is short, though. Treatments for Emerald Ash Borer in Omaha occur around mid-May to mid-June. Expect to treat your tree every other year for as long as you would like to keep your tree.
Prune Lilacs & Forsythia
Are you finding that, as your lilac and/or forsythia grow, it only gets blooms on the very end? If your once beautiful flowering plant looks drab or messy, it may be time for a prune. Plan to prune Lilacs and forsythia right after they have finished flowering for the season. Once flowers begin to wilt & wither, it's go time!
How to Prune Lilacs & Forsythia:
Remove older stems at the base of the plant to rejuvenate. Take the fattest stalks off - aiming to remove 1/3 of the oldest stalks. We recommend doing this again over the next two years. This approach will result in a better shape & a greater number of blooms.
The flowers for the following year form immediately after the current blooms fade, so timing is everything. Pruning in late summer may hinder efforts for better blooms by cutting off next year's flowers.
Did you find these tips & tricks useful?
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Questions? Ask Our Arborist
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