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Plant Diseases


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]


There may still be time to protect Prunus spp. from Taphrina leaf curl. Do you remember seeing red, curled, distorted, leaves on Prunus spp. last year and wondering what might have caused this symptom? Taphrina leaf curl, a fungal disease that survives in bark and bud scales, infects peaches and nectarines as well as ornamental…Read more about Taphrina Leaf Curl on Ornamental Flowering Peaches and Nectarines[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]


This is the time of year when growers begin planting seed—whether you are child planting a few seeds in Dixie cup for a school project, home tomato growers, or professional horticulturists. Unfortunately, one problem you may share in common is damping-off. Damping-off describes the death of seeds or seedlings and includes all of the following…Read more about Damping-off of seeds and seedlings[Read More]


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