Wet summer weather always brings in a surplus of plant diseases, but few are as dramatic as clematis blight, caused by the fungus now called Calophoma clematidina (formerly Ascochyta or Phoma clematidina) (Fig. 1). The rest of us simply call it clematis blight or clematis wilt. Why the confusion with both the common and Latin[Read More…]
Resources for landscapes and gardens in the Midwest
Landscape Report
Plant Diseases
In the last five years, we have received 233 samples from Indiana, alone, with concerns ranging from boxwood leafminer to Volutella dieback and cold damage (Figure 1, 2, 3). Often, we find multiple problems on any given sample, and very frequently we see Volutella in association with dark cankers of stems that appear to have[Read More…]
All plants are susceptible to attack by pests and pathogens. Under certain conditions, a homeowner may require the use of a pesticide, but only after they’ve included, or exhausted the use of cultural practices like removal of diseased tissue (sanitation and eradication); considered resistant varieties to replace continual problem plants; and making sure the plant[Read More…]
As we get into the throngs of summer, disease activity takes hold on the cool season turfgrass species we commonly use on lawns. This spring/early summer 2023 much of the state has been in a considerable drought, missing approximately two inches of normal precipitation in both April and May, and three inches below normal so[Read More…]
Creeping phlox (Phlox subulata) has been a reliable mainstay in home landscapes for generations. This spring-blooming perennial is also known by a string of other common names, including flowering moss, moss phlox, moss pink, rock phlox, and thrift (not to be confused with sea thrift which is Armeria maritma). Creeping phlox is native to a[Read More…]
Periwinkle (Vinca minor) has a few disease issues that can cause severe damage to Vinca in cool wet weather, including Rhizoctonia stem and crown rot, Phytophthora root and crown rot, and Phoma stem blight. The last disease, Phoma stem blight, can cause severe damage to Vinca early in Spring when new stem growth emerges (Fig[Read More…]
Each spring the PPDL receives several samples of oak trees showing curled, twisted, stunted and/or generally ratty looking leaves. When there are holes in the leaves or leaf edges are missing tissue, we add another symptom name to the mix: tatters. Distorted new growth and tatters are most common on white oaks and may occasionally[Read More…]
Pseudomonas syringae pv. syringae is an opportunistic bacterial pathogen that attacks a diversity of woody ornamental plants. The bacteria cause flower blights, cankers, shoot blights, and diebacks. Symptoms Symptoms often begin as expanding leaf spots. On lilac and viburnum, small spots expand to irregularly shaped brown lesions with yellow halos (Fig. 1). For most other hosts[Read More…]
Rose rosette disease is a severe problem for rose growers and occurs widely throughout many rose growing regions of the US, especially from the mid-South into the Midwest. The problem was described on roses in the early 1940s but actual cause of the disease remained murky until the pathogen was identified as a virus in[Read More…]
There have been a number of samples we have received at the PPDL in recent weeks that bear similar problems worth noting. It is still relatively early for significant in-season disease development due to how cold it has been, although we have certainly had enough rainfall to encourage fungal growth. We have received multiple samples[Read More…]
Two short YouTube videos demonstrate how English and Spanish speakers can use the Purdue Plant Doctor Website. Diagnosing Plant Problems with the Purdue Plant Doctor Web Page (5 minutes -in English with closed captions) Guia Rapida Diagnosticar y Manejar Problemas de las Plantas con Purdue Plant Doctor ( 9 minutes in Spanish with closed[Read More…]
Why Scout? Pathogens, insects, weeds and other pests negatively impact ornamental plant production (greenhouse, nursery, landscape). Integrated pest management (IPM) strategies are used to prevent (ideally) or mitigate damage to ornamental crops. IPM strategies of ornamentals include practices such as proper plant choice for the site, incorporation of resistant varieties when available, the use of[Read More…]
Rust diseases produce some of the most dramatic symptoms and signs we see on woody plants in the landscape. These fungi live up to the name of ‘rust’ diseases because the spore structures they produce on the plant are generally bright orange, as shown by these examples: Cedar-apple rust (https://purduelandscapereport.org//article/orange-koosh-galls-on-eastern-red-cedar/), Hollyhock rust (https://purduelandscapereport.org//article/jolly-hollyhock-rust/) and Buckthorn[Read More…]
I enjoy gardening and take pride in the variety of flowers my wife and I manage to squeeze into a few beds each Summer. This year an interesting zinnia caught my eye and ended up in our back-yard garden. After fending off rabbits early in the season a new threat emerged in July: bacterial spots[Read More…]
A new disease called Beech leaf disease (BLD), associated with native and ornamental beech trees (Fagus spp.), has been making its way eastward from Lake Erie. First observed in 2012, trees show dark interveinal leaf banding, deformation of the banding tissue, and leaf curling under increased disease severity. Leaves can be stunted and leathery in[Read More…]
Guignardia leaf blotch infects Aesculus species, which include the native plants Ohio buckeye (A. glabra), bottlebrush buckeye (A. parviflora), along with the less common painted buckeye (A. sylvatica) and red (A. pavia) buckeye. The non-native horse-chestnut (A. hippocastanum) is also a susceptible host of this disease (Fig. 1). Symptoms The fungus Guignardia aesculi (pronounced Gwin-yard-ee uh)[Read More…]
All plants can fall victim to insects, diseases, and environmental problems. How they respond to this stress is often the same: Wilting, yellowing, holes, rots, blight—it’s a long list! With so much overlap in symptoms, it can be quite a challenge for people to identify their plant health problems accurately, quickly, and inexpensively. The Purdue[Read More…]
Lilacs (Syringa spp.) are some of my favorite plants alongside Ginkgo (males, at least) and while I could wax poetic about their great aesthetic characteristics I will just say that they have beautiful spring flowers and they smell great, too. However, they do have a handful of problems that cause them to look a little[Read More…]
Brittle cinders and burnt crusts usually bring to mind bad baking experiments, but in this case they are common names for a highly destructive wood rot fungus: Kretzschmaria deusta. The names derive from the charcoal-like fungal fruiting structure (the stroma), where spores are produced (Figure 1). Most wood decay fungi can be classified as[Read More…]
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