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]

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]

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]

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]

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]

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]

Colorado blue spruce is not native to Indiana (no spruce is!), and it often suffers from environmental stresses such as drought, excessive heat, humidity, and compacted or heavy clay soils—making it an already poor choice for our landscape. If that weren’t enough, it also suffers from needle cast diseases. Needle cast is a generic term…Read more about Blue Spruce Update[Read More]