Plant and Insect Diagnostic Clinic Update - September 25, 2015

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.



We have received in the clinic several oak species with both symptoms and signs of powdery mildew. Powdery mildew is a common fungal disease found in a broad range of plants, causing cosmetic damage but would not result in plant death. Increasing the air flow throughout the canopy would help reduce the incidence of powdery mildew. To manage these pathogens, removing fallen leaves in the fall may reduce the numbers of the pathogens present in plant debris for the next year.  For more information visit the University of Minnesota yard and garden website


In the last month, the reports of Botryosphaera twig canker in oaks has increased. This disease affects twigs and branches, and symptoms include sudden browning of leaves and lesions on the stems. This disease can affect many woody plants and trees, but occurs more often on stressed trees. Therefore, promoting general tree health is the best way to control and prevent this disease. Provide adequate water and fertilizer requirements and if possible, prune affected branches under dry weather conditions. 


We have received a couple samples of turf with anthracnose or melting out. Turf anthracnose Symptoms can include foliar blight and rotting of crowns and roots. Low mowing height and extreme temperatures favor infection; especially under high humidity conditions. Management measures include proper fertilization, increasing mowing height and decreasing mowing frequency. 


Melting out is a fungal disease that may be severe this year due to the rainy season we experienced. For more information on melting out see Pamphlet SUL 0013 on the ISU Extension Store.





Minute pirate bugs are back!  These small, beneficial predators spend the summer feeding on insect eggs in the fields and gardens.  In the fall of the year and as their food supply diminishes they bite at random with a pain that is way out of proportion to their size.  Argh!


Powdery mildew on white oak.  ISU Plant and Insect Diagnostic ClinicPowdery mildew on white oak. ISU Plant and Insect Diagnostic Clinic.


Botryosphaeria twig canker on red oak.  ISU Plant And Insect Diagnostic ClinicBotryosphaeria twig canker on red oak. ISU Plant And Insect Diagnostic Clinic.


Tiny black-and-white minute pirate bugs are a common fall nuisance pest.

Tiny black-and-white minute pirate bugs are a common fall nuisance pest.


Lina Rodriguez Salamanca Extension Plant Pathologist and Diagnostician

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

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