It is easy to confuse Hemlock (Tsuga spp.) and Yew (Taxus spp.) unless you can see the overall plant habit or have them both side by side. Further confusing them is that both species may be pruned into hedges or other shapes that obscure the natural plant habits. Hemlock has short needles, 1/4 – 3/4″ long, green above and distinctly whitish silver below due to prominent white stomatal bands. Cones are 1/2 – 1″ long, ovoid, and pendulous. Yew has a slightly longer and wider needle -about 1/2 – 1 1/4″ long, dark green above and light green below, overall coarser texture compared to hemlock. Cones resemble berries, the brown seeds are covered by a fleshy red aril (seedcoat).
Avoid injury from falling ash limbs by promptly removing dead and dying ash trees. Don’t do it yourself! Hire a professional to safely remove your brittle trees.
This looks to be shaping up as a tough winter for us and our trees could be damaged, be prepared with these winter tree tips
Sitting in your back yard on a warm day under the shade of a tree is one of the joys of spring, but there are a growing number of threats that could destroy this experience. Invasive species present dangers like those from above in the form of fragile dead ash trees and from below in the form of new tick species. Learning to prevent, protect, or recover from these pests can mitigate their devastation. Emerald Ash Borer University is an online webinar series produced by a partnership between three universities and the US Forest Service that allows listeners to learn about invasive species and ask questions of experts without leaving their home or office. All webinars are free and many can be used towards continuing education programs (contact Elizabeth Barnes for details). Can’t watch it live? No problem! All webinars are recorded and posted online after the talks. To register[Read More…]
A look back at the past year may help us be alert to problems ahead. Here’s a summary of the most common problems received in the diagnostic lab on woody ornamentals in 2018. As is typical for most years there were more non-disease (abiotic) problems than infectious (biotic) diseases found on PPDL lab samples in 2018 (see Table 1). These abiotic problems include aggregate counts of everything from poor planting practices to soil conditions and environmental factors. The table also shows the most frequently diagnosed infectious disease problem was Botryosphaeria dieback or canker, which was found across a range of hardwood trees and shrubs including: Maple, Magnolia, Crabapple, Redbud and Oak. The most commonly submitted leaf disease was Tubakia leaf spot on oaks, which is usually more severe on the red oak group. We also had our first recorded samples of Bur oak blight (Tubakia iowensis) on Bur oak and[Read More…]
The time is now to start protecting your trees! Now that your ears are perked up, let’s talk a bit about Southwest injury on trees. Bark cracking (Fig.1) is a phenomenon that occurs in many species of trees and can have many causes. One of the most common types of bark cracking is termed Southwest injury. Southwest injury occurs during the winter months on the lower section of the trunk on the southwest side. This happens when there is a sudden temperature drop, for example, the sun going behind a cloud during the winter. The freeze-thaw cycle happens very quickly when there is a change from very warm to cold conditions, which results in a crack. If there is a snow pack, the reflection of sunlight on the bark will actually increase the temperature in the bark (Fig.2). Usually Southwest injury occurs on thin-barked trees, such as Acer spp., Cercis spp., Malus spp.,[Read More…]
The DNR Division of Entomology & Plant Pathology has discovered that a shipment of boxwood plants infected with boxwood blight was shipped to Indiana in May. This is important because boxwood blight (Calonectria pseudonaviculata) is a fungal disease that infests members of the popular Buxaceae family, and is often transported through the nursery trade. Hosts include Buxus (boxwood), Pachysandra (Japanese spurge) and Sarcococca (sweetbox). In total, 23 stores in Indiana received infected material in early spring (particularly “Graham Blandy” cultivar), and it’s possible that members of the public inadvertently purchased some plants. The fungus, which can lay dormant in drier conditions, can be found on all above-ground portions of the plant and presents itself as dark leaf spots. It causes rapid defoliation, which typically starts on the bottom of the plant and moves toward the top. This fungal pathogen can move through sporulation in water and from dropped leaves. As[Read More…]
Burning bush is so named for its brilliant red foliage display in autumn. But we sometimes get questions asking why their shrub fails to color up, with leaves that remain green until they drop from the plant. Fall color or lack thereof is affected by a number of factors, including genetics of the plant and environmental conditions such as temperature, soil moisture, nutrition, and sunlight. If a particular specimen fails to perform over multiple years it is likely that the plant lacks the genetic disposition for good fall color. This is not likely to improve over time. Burning bush, also known as firebush, is considered an invasive plant in many states and is listed as a medium threat on the Indiana Invasive Species Council invasive plant list. https://www.entm.purdue.edu/iisc/invasiveplants.html This could be an opportunity to consider replacing burning bush with one or more of the following alternative shrubs with attractive fall[Read More…]
Tree in the built environment often need supplemental nutrition to improve growth and resist pests. Fall fertilization can help trees get off to a healthy start next growing season.
Bacterial leaf scorch (BLS) on oak is a systemic disease caused by the bacterium Xylella fastidiosa (Xf) (Fig 1). The bacteria live in the xylem vessels (water conducting elements) and restrict water flow. Xf is transmitted from tree to tree by xylem-feeding insects such as leafhoppers and treehoppers. Numerous woody hosts are susceptible to various strains of Xf . Symptoms of bacterial leaf scorch may vary somewhat between oak species. On pin oaks, scorching appears along the leaf margins and progresses inward toward the mid-vein (Fig 2). There is often a yellowish margin between the scorched leaf tissue and green tissue. On other red oaks, the scorch typically appears at the leaf tip and progresses up the leaf towards the petiole (Fig 3). Branches with leaves that appear to be healthy may be interspersed on the same tree amidst branches with scorched, diseased leaves (Fig 4). Leaf scorch and premature[Read More…]