Hakone grass (Hakonechloa macra), also known as Japanese forest grass, is often used for massing in beds in where a low maintenance ground cover is needed in semi-shaded areas. The graceful arching stems along with the availability of gold or white striped variegated cultivars make it an attractive option. There are few reports of disease…Read more about Gray leaf spot/blight of Hakone Grass[Read More]
Resources for landscapes and gardens in the Midwest
Landscape Report
Plant Diseases
Volutella stem and leaf blight, caused by the fungal pathogen Coccinonectria pachysandricola (=Volutella pachysandricola), can cause major damage to Pachysandra – destroying large areas in a bed. (Fig 1) Infected leaves first develop tan or brown blotches with dark brown margins, which expand, often with concentric lighter and darker target-like zones. (Figs 2a,b) Stem and…Read more about Volutella leaf blight and stem canker of pachysandra[Read More]
Fungal diseases of ornamentals will always be a limitation to profitable plant production and management—how significant that limitation is in your hands. Fungicides are effective in reducing the risk of loss– in numbers, in quality and in terms of aesthetics. However, fungicide costs in terms of product cost, number of applications and labor need to…Read more about Fungicide Costs[Read More]
A look back at the past year may help us be alert to problems ahead. Here’s a summary of the most common problems received in the diagnostic lab on woody ornamentals in 2018. As is typical for most years there were more non-disease (abiotic) problems than infectious (biotic) diseases found on PPDL lab samples in…Read more about Woody Ornamentals Summary 2018[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…Read more about Boxwood blight found in Indiana[Read More]
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…Read more about Bacterial Leaf Scorch of Oak: Lab Confirmation Necessary[Read More]
Tubakia leaf spot, a fungal disease, infects all species of oak. However, oaks in the red oak group such as black, red and pin oak, appear to be most susceptible. Symptoms on oak include small to large dark brown or reddish-brown spots or blotches. (Figs 1,2,3) Spotting that occurs on leaf veins may cause large…Read more about Tubakia Leaf Spot on Oak—A Yearly Event[Read More]
Oak wilt has been found in most counties in Indiana and is one of the most serious threats to the health of oak trees in the Midwest, especially those in the red oak / black oak group. The disease is caused by the fungus Ceratocystis fagacearum and is spread from tree to tree by sap…Read more about Oak Wilt in Indiana[Read More]
Boxwoods losing leaves should not be ignored!! Check them carefully for tell-tale symptoms of boxwood blight, a serious fungal disease that causes rapid defoliation and dieback (Fig. 1). The fungus that causes boxwood blight can infect all above ground portions of the shrub. The first symptoms of the disease are dark leaf spots (Fig. 2…Read more about Boxwood Blight – Be on the Look-Out[Read More]
Diseases that affect the twigs, branches, and the main trunk of a tree are referred to as cankers or blights. Cankers appear as a general sunken area of darkened tissue on the twigs or branches, often surrounding a branch stub (Fig. 1). Canker diseases can be a serious problem in the landscape when they are…Read more about Opportunistic canker pathogens[Read More]
Getting calls from panicked customers about black spots on maple leaves? You’re probably not alone, because now is the time when people start to notice maple tar spot. Every summer we get questions about black spots on maple leaves that look like tar. These spots are not actually “tar” on maple, but are rather a…Read more about Tar Spot on Maple[Read More]
This article, and many others, will be presented at the 2018 Purdue Turf and Landscape Field Day on July 10th. Registration is open and available online: https://www.mrtf.org/event/turf-and-landscape-field-day/?event_date=2018-07-10 Here is the lineup for the field day. A cultural weed control method is one that involves steps to reduce or eliminate weeds via maintenance techniques. In landscapes, the…Read more about Cultural Plus Chemical=A good weed control combo in landscape beds[Read More]
Fungi are a unique group of organisms—so unique that they are put into a separate category called a ‘Kingdom’. In Kingdom Fungi, some members cause rust, scab, powdery mildew, leaf spots and blights (to name but a few!). When these fungi are ‘out of control’ many people turn to fungicides. What are fungicides and how…Read more about Kingdom Fungi[Read More]
The Purdue Plant and Pest Diagnostic Lab (PPDL) recently received samples of Mugo Pine and Spruce that exhibited reddish-brown bands on needles of lower branches (Figs 1 & 2). Microscopic examination of needles confirmed the presence of Dothistroma,(Fig 3) a fungus that causes red band needle blight. Needles infected with Dothistroma first exhibit dark green…Read more about Red Band (Dothistroma) Needle Blight[Read More]
Arborvitae varieties (Thuja spp.) provide some of our most beautiful and versatile evergreens for landscapes, with an extensive selection of sizes and types. Unless they get proper care, they also give us some frustrating failures. Here is my list of the most frequently encountered ‘Arborvitae Aggravations’, based on the samples and questions we get in…Read more about Top Arborvitae Aggravations[Read More]
Xanthomonas is both an unfortunate, but regular occurrence in the greenhouse industry. Despite the efforts from numerous companies to supply ‘clean plants’, Xanthomonas (and other bacterial pathogens) regularly slip through. This year, it came in on begonia. The pathogen. Xanthomonas is a genus of yellow colored bacteria that infect many species of plants (approximately 400!),…Read more about Begonia Bacteria Brouhaha[Read More]
The recent jump from Winter to Summer (with 2-3 days of Spring somewhere in there) got folks out looking at Tulips in full bloom now in northern Indiana. The only thing marring the view in one local planting was an outbreak of tulip fire, caused by the fungus Botrytis tulipae. The disease first shows up…Read more about Tulip Fire[Read More]
Three different rust fungi cause gall-like protrusions on eastern red cedar (Juniperus virginiana) trees. The bright orange gelatinous galls with tendril-like protrusions (Fig 1) resembling ‘koosh balls’ are caused by Gymnosporangium juniperi-virginianae. This fungal disease is known as Cedar Apple Rust. The galls develop on the cedar tree (Fig 2) and ‘sprout’ fungal spore-bearing tendrils during…Read more about Orange ‘Koosh’ Galls on Eastern Red Cedar[Read More]
A group of samples of several varieties of blue holly (Ilex x meservae) arrived in the lab from a commercial nursery in late January with a common problem, yellowing and rapidly dropping leaves and general poor growth (Fig. 1). After ruling out disease and insects on the foliage we next checked the root systems. After…Read more about PPDL Case Study #2: Sickly blue holly[Read More]
Purdue’s Plant and Pest Diagnostic Lab (PPDL) receives more than 2000 samples for diagnosis each year. We’ll highlight some of the more interesting cases in the Purdue Landscape Report in brief case studies like this. PPDL Case Study #1: White Fungi on Crabapple Branch Earlier this year a landscaper submitted several photos of a crabapple…Read more about PPDL Case Study #1: White Fungi on Crabapple Branch[Read More]
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