Plant and Insect Diagnostic Clinic Update - June 10, 2016

The following are highlights and updates about samples and questions recently received in the Plant and Insect Diagnostic Clinic. Visit the PIDC's Facebook page to ask questions and for updates and more pictures.

Broadleaf Trees

We have confirmed several cases of anthracnose on shade trees in the last three weeks. For more information about anthracnose visit our article Anthracnose on shade trees at


Oak tatters are popping up! the new growth of the tree should not be affected as this is considered a temporary condition. For more information on oak tatters visit our article  


Elderberry rust was spotted just today. This may look like a flower from the far but is, in fact, a fungal pathogen (Puccinia bolleyana) that colonizes the elderberries leaves and causes the tissue to curl (see picture). The yellow structures are the fungal bodies. This rust need two hosts (elderberry and sedges) to complete its life cycle. If you see these symptoms in your elderberry or something similar, we can help it diagnose it. Would it have an impact on m y elderberry harvest? Not likely, only if the plant is covered with symptoms (severe cases are not very common). What to do about it? Prune the symptomatic twigs and destroy them.


If you are concerned about Bur Oak Blight please see our new and updates Bur oak blight article at

Coniferous Trees


We have confirmed Dothistroma needle blight, SNEED, and the needle casts caused by the fungi Rhizosphaera and Stigmina in different coniferous hosts. It was also brought to our attention that one of the commonly used fungicide products containing chlorothalonil to protect new grown in conifer form fungal disease, now restrict its use in blue spruces. This is a good remainder always to read and follow the label instructions and restrictions.



We continue to receive inquiries on powdery mildew management in lawns. See our recommendation at


We confirmed several cases of the bacterial disease fire blight in apples, pears, and crabapples. The symptoms of fire blight can be confused in some cases with frost injury, heat damage (due to controlled burns around trees), chemical damage, and possibly bacterial blast, a condition that occurs in near-freezing weather. All these conditions have some differences when it comes to management tactics and future implications. If you suspect your tree may be suffering from fire blight, do not guess!! Get a confirmation sending us a sample. We will need a 3 to 5 branches including blighted shoots and green leaves (  For more information on fire blight visit 

Rust on an elderberry leaf
Rust symptoms and sign on elderberry.


Lina Rodriguez Salamanca Extension Plant Pathologist and Diagnostician

Dr. Lina Rodriguez-Salamanca is an extension plant pathologist and diagnostician with the Iowa State University Plant and Insect Diagnostic Clinic  (, a member of the National Plant Diagnostic Network (NPDN,&nbsp...

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