Biology: Common chickweed (Stellaria media) is a winter annual broadleaf weed. In lawns, it forms dense, prostrate patches throughout North America, but can grow relatively tall in the landscape. Common chickweed germinates from seed in late summer or early fall. However, germination timings can vary throughout the year if conditions are shady, and moist enough. Identification: Common chickweed is predominantly a winter annual broadleaf weed that can be identified by its prostrate growth habit and leaf shape. Common chickweed leaves are located opposite each other on stems that may be hairy on older portions and smooth on newer growth. Additionally, leaves are light green, smooth, and oval- to egg-shaped that come to a point at the apex. Leaves located on the upper portions of the stems have no petioles (leaf stems) while leaves located lower on the stems have long, sparsely-hairy petioles. Common chickweed produces small clusters of white flowers with five[Read More…]
Archives for October 2018
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…]