Skip to content

BLS has been very damaging to red oaks in Delaware and the Mid-Atlantic states since the early 1990’s

BACTERIAL LEAF SCORCH (BLS) of hardwood trees, shrubs, and herbaceous plants, is caused by the bacterium, Xylella fastidiosa, carried by small insects such as leaf hoppers and sharpshooters. BLS has been very damaging to red oaks in Delaware and the Mid-Atlantic states since the early 1990’s. Northern red oak and pin oaks under environmental stress are more susceptible. Symptoms include marginal discoloration or scorch of leaves in late summer or early fall, often with a yellow or dark band on the inside edge of the discolored area. Symptoms are similar to those caused by drought or root issues that interfere with flow of water and nutrients. Plants may not develop symptoms for a year or two after infection, but then thinning of branches occurs and trees die within 5 to 8 years.  Infection is confirmed with a lab test for a fee, so if confirmation is needed, please arrange to have samples tested by contacting the UDBLS Red Oak 2016 Plant Diagnostic Clinic. Please note that there is a $20 fee for BLS testing. To manage, maintain good tree vigor, and remove infected trees. A UD fact sheet has more info:
NFG 8/30/2016

CHICKEN OF THE WOODS or the sulphur shelf fungus (Laetiporus Laetiporus sulphureus Newark DE 2016sulphureus) has been seen at the base of trees with large bright yellow and orange overlapping fruiting structures. These fungi are some of the most colorful and identifiable fungi found on living or dead trees. Chicken of the woods is a choice edible, but must be positively identified by an expert. It is one of many fungal species that attack the heartwood of trees, and produce fruiting bodies on the trunk. Laetiporus is common in oak trees, as many of these Basidiomycetes are found in association with certain trees. If one tree has heart rot, it doesn't mean that nearby trees will get it, even if they are of the same species. The fungus must enter through a wound in order to become established, and the fungus will slowly decompose the heartwood, the dead wood or center of the tree. By the time a fruiting body is produced on the trunk of a living tree, it usually means that the fungus has been there for years. At this point there is no control but to keep tree stress low. Rotting of the interior wood can weaken the tree, leading to breakage, insect damage, and other diseases. An arborist may be able to prune to save the tree.
NFG 8/21/16

Phytophthora Resistant Plants

Phytophthora root rot OlsonPhytophthora root rot, a soil borne disease caused by a fungus-like organism, is a widespread problem which can affect many woody and herbaceous landscape plants. Azalea, holly, rhododendron, and juniper are the most frequently affected plant groups in the eastern landscape. Submit a sample including roots to the Plant Diagnostic Clinic and it can be tested for Phytophthora. An infested site should not be replanted with susceptible hosts. Increase drainage and plant a more resistant shrub or tree. The best control for Phytophthora is to avoid getting it started in the first place. Phytophthora is favored by planting susceptible species and cultivars in poorly drained soils, or by overwatering in sites with adequate drainage. Once a Phytophthora problem is established in a landscape site, the best option is to remove the affected plants and replace with resistant species. Some good choices include Clethra alnifolia (summersweet), Itea sp (sweetspire), Physocarpus opufoliius (Eastern ninebark), and Leucothoe fontanesiana. Examples suggested by extension agents in North Carolina include Nandina, Chinese holly (cultivars including 'Rotunda', 'Dwarf Burford' and 'Carissa'), liriope, Indian hawthorn, and Camellia sasanqua cultivars (Camellia japonica is highly susceptible). The rhododendron hybrids: ‘Caroline’, ‘Martha Isaacson’, ‘Professor Hugo de Vries’ and ‘Red Head’ are considered resistant. In addition, the azalea cultivars 'Formosa', 'Fred Cochran', 'Fakir' and 'Corrine Murrah' are considered highly resistant. Other resistant azalea cultivars include Rhododendron poukhanese, ‘Formosa’, ‘Fakir’, ‘Corrine Murrah’, 'Merlin', 'Hampton Beauty', 'Higasa', 'Pink Gumpo' and 'Delaware Valley'. Susceptible cultivars include 'White Gumpo', 'Hinodegiri', 'Hershey Red', 'Coral Bells', 'Pink Pearl' and 'Hino Crimson'. Susceptible cultivars are the most widely planted, due to desirable horticultural characteristics. Resistant hybrids are not immune to disease, but more tolerant. Chemical control is generally not practical for the homeowner, and involves a drench or injection by a certified applicator.
NFG 10/2014