Kansas State University

search

K-State Turf and Landscape Blog

Category: Trees

Kansas Officials Confirm Emerald Ash Borer in Nemaha County

Posted on by Teresa Roberts

By Pat Melgares, K-State Research and Extension news service

The Kansas Forest Service has confirmed the presence of the emerald ash borer on a private residence in Nemaha County, the second new sighting found in a Kansas county this year.

closeup, emerald ash borer damage on tree limb
Emerald Ash Borer damage on tree limb

KFS, working with the Kansas Department of Agriculture and K-State Research and Extension, confirmed a live insect on Oct. 14. Officials say the pest had been suspected in the area for several years, but only recently have they found a live insect, which is required to make the detection official.

Earlier in 2024, state officials confirmed the presence of the emerald ash borer in Lyon County.

The emerald ash borer is an exotic, invasive beetle from eastern Russia and northeastern Asia that likely was brought to the U.S. in infested packing material. The beetle threatens urban and rural forests by killing North American ash species and their cultivars.

KFS officials note that at least 70 million ash trees have already been destroyed due to the emerald ash borer, and as many as 9 billion North American ash trees will eventually be functionally rooted out and destroyed from the continent.

The discovery in Nemaha County makes 15 Kansas counties in which the emerald ash borer has been confirmed, including Wyandotte (2012), Johnson (2013), Leavenworth (2014), Douglas (2015), Jefferson (2015), Atchison (2016), Doniphan (2017), Shawnee (2017), Miami (2019), Jackson (2019), Brown (2022), Osage (2022), Franklin (2023) and Lyon (2024).

See map of current counties affected in Kansas.

Forest officials say landowners should learn the signs and symptoms of emerald ash borer in their ash trees, including thinning canopies. As the feeding progresses, trees may begin to sucker (a process called epicormic sprouting) where branches appear near the trunk or lower canopy. Eventually, small D-shaped holes may appear in the bark.

Landowners are encouraged to create a replacement plan for the ash trees on their property to ensure a continually healthy canopy as ash trees decline. A landscape with many types of trees is more resilient to insect, disease and environmental threats that exist or could occur in the future.

Those seeking treatment or removal of ash trees in a county where the insect has already been detected should consult an arborist. A listing of certified arborists in Kansas is available online.

Landowners, especially those in counties where the insect has not already been detected, are encouraged to report suspected cases of emerald ash borer to the Kansas Department of Agriculture, or to the Kansas Forest Service.

All Kansans are reminded of the recommendation to avoid bringing firewood from another state or county where emerald ash borer has been previously detected. Use local sources for firewood.

The Kansas Forest Service, in partnership with K-State Research and Extension, continues to offer workshops and educational training in counties with detected populations of emerald ash borer, as well as those communities not yet affected by the pest.

More information on resources about treatment of infected trees is available online from the Kansas Forest Service.

Mimosa Webworm Causing Noticeable Damage

Posted on by Teresa Roberts

By Dr. Raymond Cloyd, Professor and Extension Specialist

Mimosa webworm, Homadaula anisocentra, larvae or caterpillars are causing noticeable damage to honey locust, Gleditsia triacanthos, and mimosa, Albizia julibrissin, trees throughout Kansas.

The caterpillars are 1/2 of an inch (12.7 millimeters) long when full grown (Figure 1) and move backward rapidly when disturbed. The caterpillars web leaves together on the ends of branches (Figure 2).

Caterpillars create webs near the tops of trees, which protects them from natural enemies (parasitoids and predators) and insecticide spray applications. Trees heavily infested with mimosa webworm are brown or scorched in appearance (Figure 3).

The caterpillars eventually depart from trees using a silken strand before pupating. Mimosa webworm pupates in bark crevices or the pupae are attached to structures (e.g. buildings). There are two generations per year in Kansas.

It is too late to apply an insecticide this time of year when trees are heavily infested with webbing because the caterpillars are protected from insecticide spray applications inside the leaf webbing. However, next year, you can manage mimosa webworm caterpillars by applying an insecticide when the caterpillars are initially present and exposed to insecticide spray applications. You can use insecticides that contain the following active ingredients: Bacillus thuringiensis subsp. kurstaki, spinosad, bifenthrin, cyfluthrin, and permethrin. Read the label of each product to ensure that “webworms” are listed. Bacillus thuringiensis subsp. kurstaki and spinosad are stomach poisons so mimosa webworm caterpillars must ingest the spray solution on the leaf surface in order to be killed. High volume spray applications should be used so that the insecticide contacts the caterpillars or there are residues on the leaf surface. If feasible, selective pruning quickly removes isolated or localized mimosa webworm infestations.

Mulch Rings Around Trees in Turfgrass

Posted on by Teresa Roberts

By Cody Domenghini, Assistant Professor, Landscape Management

A mulch ring is a circular border surrounding a tree commonly made of organic material such as wood chips. Trees planted in turfgrass should have mulch rings installed around them for a couple of reasons. Creating a mulch boundary around trees prevents lawn maintenance equipment such as string trimmers and mowers from getting too close to the trunk and causing damage. When grass is allowed to grow right up to the trunk the tree roots are in competition with the turfgrass for water and nutrients. A mulch layer over the root zone eliminates this conflict.

Ideally, trees should be planted in a landscape bed rather than in the middle of a lawn. However, when grown in a lawn, trees should have a mulch ring at least three feet in diameter for every inch of tree trunk caliper surrounding them.

Measuring tree trunk caliper of a young tree planted in turfgrass.

The mulch should resemble the shape of a donut with the center of the ring creating a 4-6” gap between the trunk of the tree and the start of the mulch. The space between the tree trunk and the mulch ring allows oxygen and water to easily reach the roots and prevents the risk of rot at the base of the trunk.

Example of a donut shaped mulch ring with the mulch not touching the tree trunk.
Volcano mulching

Avoid the common mistake of “volcano mulching”. Layer the mulch 2-4” deep. Throughout the year the mulch will breakdown, contributing organic matter to the soil and improving soil quality. Mulch should be reapplied annually. When adding a tree ring to an already established tree in a lawn, carefully remove the sod from the top few inches to not damage any tree roots.

Adding a mulch ring to an established tree.

Mulch rings for large trees should be large enough to create a barrier between the edge of the turfgrass and the trunk of the tree to prevent damage to the trunk from mowing equipment, but do not necessarily have to follow the size guidelines advised for younger trees. Adding tree rings and mulch around trees is best done in the spring, but can be completed anytime of the year.

Below is a link to an extension article discussing the proper way to mulch trees.

https://www.johnson.k-state.edu/lawn-garden/agent-articles/trees-shrubs/how-to-mulch-trees.html

Now is the Time to Scout for Bagworms

Posted on by Teresa Roberts

Article derived from KSRE News Story: Now is the Time to Scout for Bagworms

Patience and persistence is key when trying to manage bagworms. Begin scouting in early May, and depending on weather conditions – through early summer.

Once caterpillars emerge, they begin feeding on the host tree or shrub, creating their protective bags. In addition to emergence over time, young bagworms can ‘blow in’ – called ‘ballooning’ – from neighboring plants on silken threads, which increases the importance of treating multiple times during the growing season. Watch both conifers and deciduous trees and shrubs. Although defoliation of deciduous trees and shrubs don’t typically affect long-term health of trees and shrubs, extreme defoliation of conifers can cause stress or kill conifers outright.

Bagworm feeding on plant foliage, photo by Raymond Cloyd

Hand removing and destroying bagworm bags is an option for smaller infestations. For larger infestations, the bag provides protection from insecticide treatments, so it’s important to apply applications when the bagworms are young. Apply insecticides weekly when young bagworms are present, up to 5 weeks. Treat windbreaks, Christmas trees, and ornamental landscape trees as soon as bagworms are present to prevent bagworms from causing substantial plant damage. Thorough coverage is important, including penetration into the interior plant canopy and upper branches.

Bagworm bags hanging from a tree branch, photo by Raymond Cloyd

Many insecticides are labeled for bagworms, but timing of application and thorough coverage will ensure the effectiveness of insecticides in managing bagworms. When bagworm caterpillars are small (1/8 to 1/4 of an inch long), products containing Bacillus thuringiensis subspecies kurstaki (Btk) or spinosad as the active ingredient can be effective. These insecticides have minimal direct impact on beneficial insects compared to broad-spectrum insecticides, which could lead to outbreaks of spider mites or scale insects that can cause damage to treated trees and shrubs.

If insecticides are not applied when bagworm caterpillars are small (1/8 to 1/4 of an inch in length) then broad-spectrum insecticides, including those containing malathion, acephate, or cyfluthrin as the active ingredients can be applied. Be sure to read the product label and follow directions.

For more information on controlling bagworms, reference the publication, Bagworm: Insect Pest of Trees and Shrubs, written by Dr. Raymond Cloyd.

Pine Problems in Kansas

Posted on by Teresa Roberts

By Judy O’Mara, Diagnostician, K-State Plant Disease Diagnostic Lab

It was pretty cold in mid-January 2024, the low temps in January sent me to the K-State Mesonet (https://mesonet.k-state.edu/weather/historical/) to take a closer look at the weather patterns during that time period. The Mesonet is a collection of weather stations across Kansas that can be used in a variety of ways but my favorite is to take a look BACK in TIME at the historical weather patterns. The temperature dropped pretty low on Jan 14th (-10.5F) and Jan 15th (-10.6F) in Manhattan, KS. Brrr.

In any given year, it is not uncommon to see extreme weather patterns impact plant growth and health. Winter damage to pine trees frequently shows up on the north or northwest side of the tree, although it can hit the top of the tree as well. Winter damage can hit multiple trees or can show up on scattered trees within a planting. The outer needles tend to be scorched with the inner needle growth remaining green. The more exposed foliage is more susceptible to desiccating winter winds. Winter damage on pine trees can be confused with some common Kansas pine diseases such as pine wilt, Diplodia pine tip blight and Dothistroma needle blight.  One tip that can help to differentiate between these problems is the TIMING of the damage. Pine trees generally enter the winter looking good and then get hit by low temperatures and/or desiccating winds sometime between December-February. A look at the K-State Mesonet can help pinpoint the weather event that caused the damage.

Winter damage can look pretty dramatic but it is best to wait until early to mid-May to assess recovery potential. Even though the pine needles are scorched, the dormant buds frequently escape damage and push out new growth in the spring. The damaged needles eventually shed and the overall appearance of the tree will gradually improve. Another quick way to check recovery potential is to pop off a few buds at the end of the branch and see if they are still green inside.

Winter damage can be confused with some common Kansas pine diseases. For help sorting out these problems reach out to your local county extension office. The K-State Plant Disease Diagnostic Lab can also provide assistance.  https://www.plantpath.k-state.edu/extension/plant-disease-diagnostic-lab/

Pushing Snow

Posted on by Cheryl Boyer

Many of you are busy “pushing snow” with the recent cold weather, and there will likely be more snow to push in the next couple of months. Please take a few minutes to train your staff on protecting ornamental plants when clearing hard surfaces like parking lots.

While clearing the lot, driveway, or sidewalk is the most critical objective, “do no harm” should also be a goal. Far too many plants are crushed by the push and weight of snow in winter months. Sometimes, the mystery summer problem is actually a clear winter problem.

There is a tendency to pile snow on top of green spaces in parking lots. However, plants in those spaces continue to need to photosynthesize (evergreens) and exchange gases and are likely to die or suffer severe dieback if the cold weather persists and the snow takes a significant time to melt. Piling snow in planting areas can also contribute to soil compaction and root decline, causing problems later in the growing season.

De-icing chemicals are often mixed into snow that is pushed into landscape settings. As the snow melts, it dumps salt into the planting area, damaging shoots and roots for the long term. To minimize the landscape impacts of clearing snow, consider alternative de-icing salts like calcium chloride and calcium magnesium acetate and follow the label instructions when possible. Sand can also help provide traction.

With your staff, practice identifying an appropriate place to pile snow that isn’t in landscape areas, offers a place to collect runoff, and won’t result in slush that can splash onto plants. When possible, make these decisions before snow is on the ground—snow can cover a lot of detail and make it easy to lose track of the areas that need to be preserved.

Study each site individually and develop a plan for human, pet, and plant safety when winter storms hit to avoid problems in the future and establish trust with your clients.

How to Protect Trees from Elm Leaf Beetles

Posted on by Teresa Roberts

By Maddy Rohr, K-State Research and Extension News Service

Prevent damage now by using insecticides, says K-State horticulture expert.

Managing plant pests is a common garden task, but Kansas State University horticulture expert Cynthia Domenghini says using preventive methods in the fall also is important.

“There are typically two generations of elm leaf beetles each year,” Domenghini said. “They overwinter as adults and emerge from their protective shelters in early spring. As elm trees develop leaves, the beetles move in and females begin laying eggs.”

Young Elm Leaf Beetle larvae are dark-colored, hairy grubs. Older larvae are yellow with two long, dark stripes. Adult beetles have green and yellow stripes.

“Larvae hatch and spread throughout the tree to feed. Larvae reach maturity within four weeks and seek shelter to pupate,” Domenghini said. Larvae may travel to the bottom of the tree or in cracks of bark.

Domenghini said larvae cause most of the damage by skeletonizing leaves of elm trees. Adult beetles chew holes through the leaves resulting in a change of color to brown and dropping.

Preventive methods include several insecticides. Healthy trees that have not been greatly affected should not be sprayed in the fall.

Larvae and adult sprays include acephate (Acephate, Orthene), spinosad (Natural Guard Spinosad, Conserve, Captain Jack’s Dead Bug Brew, Monterey Garden Insect Spray), lambda cyhalothrin (Scimitar, Spectracide Triazicide).

Domenghini and her colleagues in K-State’s Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for maintaining home landscapes and gardens. The newsletter is available to view online or can be delivered by email each week.

Article originated from K-State Research and Extension News

Kansas Forest Service Hosting November Workshops

Posted on by Teresa Roberts

Join the Kansas Forest Service Community Forestry Program for statewide workshops in November!  You’ll learn more about the recently completed canopy assessment for all incorporated cities in Kansas, how you can utilize your community’s data and the values of your community’s tree canopy. Biotic and abiotic impacts to community trees, pruning strategies to reduce canopy loss and how to reforest your community will round out these four-hour workshops.

Registration for the day is $5. All programs will run from 8:30am – 1:00pm. ISA CEUs will be available.

Continue reading “Kansas Forest Service Hosting November Workshops” →