We are in the swing of the holiday season and Christmas decorations, ranging from trees to living wreathes, are for sale at stores. Thinking ahead, you might already have in mind how to dispose of plant material after the holidays, but it is important to take into consideration an important pillar of plant disease management[Read More…]
Resources for landscapes and gardens in the Midwest
Landscape Report
Plant Diseases
Northern red oak (Quercus rubra) is a Midwest native and is generally well adapted to growth across much of the region, but we get questions about dieback or ‘flagging’ on it fairly regularly. The two most common causes of twig dieback on this host are Kermes scale (Allokermes galliformis and A. kingii) and fungal canker/dieback[Read More…]
Black root rot (BRR), caused by the fungus Thielaviopsis basicola,has a host range of several hundred plants. In the landscape, the most common hosts include pansies (Fig. 1), and vinca, along with calibrachoa and petunia. In perennial hosts, it often infects lavender, phlox, milkweed and butterfly-weed (Asclepius spp.). Even woody plants, like holly and elderflower[Read More…]
Junipers have to be my favorite group of evergreens, behind a select few pine species. They have a fantastic fragrance, are evergreen, many can tolerate drought, are an ingredient in gin (definitely a bonus), and work well in a variety of landscape uses, including as a barrier plant. They look great year round, except when[Read More…]
Contorted filbert is an ornamental cultivar of European Filbert, (Corylus avellana ‘Contorta’), grown for its twisted, gnarly stems. The plant is also sold under the name Harry Lauder’s Walking Stick. While it’s unique architecture can be impressive, it’s highly susceptible to a fungal canker that can cause extensive damage to the tree. Eastern filbert blight[Read More…]
Are you noticing bright yellow, white and brown blobs on wood chip mulch? These growths are known as slime molds. Slime molds are not parasitic and therefore do not cause disease. Slime molds get their nutrients from bacteria and small bits of organic matter which is why it is common to see them growing on[Read More…]
How are your plant identification skills? Personally, without a reference, I tend to have difficulty identifying some of the less commonly used trees in the landscape. However, being a disease diagnostician/plant pathologist I do have a fallback strategy – the diseases. One of the key points here is some symptoms are so characteristic of, or[Read More…]
First identified on coleus in the US in 2005, downy mildew has become an annual threat to production of this popular annual. The disease may be caused by the pathogens Peronospora lamii (also infects basil, as well as several species of Salvia and Lamium) or P. belbaharii (also infects basil). The symptoms may range from[Read More…]
Rhizoctonia is not very picky. The fungus has a very wide plant host range where it can act as an endophyte, not causing damage to the colonized plant; a mycorrhizal symbiont, in some cases being essential for the hosts survival, like in some orchid species; and, as we commonly see it, a pathogen that causes[Read More…]
Rhizomatous bearded iris (Iris x germanica) is a favorite early spring perennial; however, it is routinely troubled by a fungal leaf spot that tends to appear soon after flowering (Figure 1). These start as small wet-looking lesions that may quickly enlarge into larger spots with brownish edges, tan centers and yellow margins (Figure 2). When[Read More…]
Sign-up to receive email news and alerts from Purdue Landscape Working Group:
