Arborvitae (Thuja spp.) fulfill several crucial roles in the landscape, especially windbreaks and screens (Fig. 1). Their relatively fast growth habit, wide variety of available forms, and inexpensive price point make them one of the most common conifers in the Midwest landscape. Due to the ubiquitous use of arborvitae, and their perceived problems, the Green[Read More…]
Resources for landscapes and gardens in the Midwest
Landscape Report
Plant Diseases
Botrytis blight (also called grey mold) is caused by fungi in the genus Botrytis. The best known of these fungi, Botrytis cinerea, can infect many different hosts, including soft fruit, vegetables, annuals, perennials, shrubs and young tree seedlings (Fig. 1). Other common species of Botrytis are more host specific, including Botrytis elliptica (infecting only lilies[Read More…]
If you have ever seen gooey neon orange branches on trees and shrubs you may have been observing a phenomenon commonly known by the very scientific name of ‘orange goo’. Appearing in cool, wet weather during spring sap flow, the goo is caused by fungi, bacteria and yeast colonizing tree sap, especially where an injury[Read More…]
Roses are a popular landscape and garden plant in Indiana. Black spot, caused by the fungus Diplocarpon rosae, is the major foliar disease of roses in Indiana. Infected leaves develop black spots, turn yellow and drop prematurely from the plant. Premature defoliation decreases plant energy reserves and results in reduced flowering of roses as well[Read More…]
Ascochyta blight is a sporadic disease that can infect Kentucky bluegrass, tall fescue and perennial ryegrass. Outbreaks are closely tied to high rainfall or irrigation events in mid to late spring, and drainage patterns. If the lawn is irrigated, Ascochyta can be a sign of too much irrigation. Current rainfall events are providing a prime[Read More…]
To effectively control Taphrina leaf curl fungicides must be applied before bud swell. If you remember seeing red, curled, distorted, leaves on Prunus spp. last year (Figs 1,2) and wondered what might have caused this symptom, the answer is most likely Taphrina leaf curl. Taphrina is a fungal disease that survives in bark and bud[Read More…]
One of the most common diseases found on boxwoods is Volutella blight and dieback, caused by the fungi Pseudonectria foliicola and P. buxi. Both fungi are considered weak pathogens, always around but not causing much damage until plants are injured or stressed, rarely infecting otherwise healthy plants. Volutella blight alone usually doesn’t kill boxwoods, but[Read More…]
Determining the cause of dieback and decline symptoms in landscape trees can be very difficult due to the many cultural, environmental, and biological factors that could be involved. The first place you should look for a culprit when dealing with this type of tree problem is the base of the trunk and the roots. Stem[Read More…]
Galls are gnarly-looking problems for plants and now is the perfect time to be looking for galls on woody ornamentals in the landscape. Without their leaves, these abnormal growths on branches can be easy to spot as you look through the open canopy (Fig 1). There are many different types of galls or gall-like structures[Read More…]
Hair ice, also called ice wool, frost beard, and gnome beard is ice that appears like silky hair (Fig. 1) but forms on dead wood colonized by the fungus Exidiopsis effusa. It is fairly uncommon and not reported in Indiana…but who has been looking for it? Think of the bragging rights! It has been found as[Read More…]
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…]
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…]
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