Plant and Insect Diagnostic Clinic Update – July 28, 2017

Marssonina Leaf spot symptoms.  Photo credit: Lina Rodriguez Salamanca, Iowa State University Plant & Insect Diagnostic Clinic.  

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. For more information on a particular disease or insect problem listed, follow the article cited.


The following plant disease highlights represent recent sample submissions from fruit, vegetables, and ornamentals. 

Broadleaf Trees

Poplar- Marssonina leaf blight, see US Forest Service factsheet at Marssonina Leaf Blight  

Coniferous Trees

Spruce- Sudden Needle Drop

Black Hills Spruce-  Stigmina needle cast

Marssonina Leaf Spot, caused by Marssonina spp (M. populi  and M. brunnea)
Evidence (signs) of the fungal pathogens Marssonina spp (M. populi and M. brunnea) that cause Marssonina Leaf Spot in poplar. Photo credit: Lina Rodriguez Salamanca, Iowa State University Plant & Insect Diagnostic Clinic.  

Perennials and Annuals

Lily- Daylily Leaf Streak, resource from Clemson


Creeping Bentgrass- Anthracnose

Creeping Bentgrass- Nematodes (ring and lance nematodes)

Fruit (small and tree fruit, including hops)

Grape-grape downy mildew and grape black rot

Raspberry- cane blight, see the Ohio State University resource on cane blight   



In the past month Iowans have rediscovered or newly discovered the joys of Japanese beetles!  These voracious beetles feed on a wide variety of plants. Commonly damaged are linden, birch, roses, and grapes.  Beetles emerged in late June and they will live about 6 weeks.  Some areas are reporting populations decreasing, while in others things are still going strong.  We are hearing from locations in the western half of Iowa that this is the first time they have observed such extensive damage.

We have received several bat bug samples this summer.  Bat bugs look very similar to bed bugs, but have longer body hairs.  Close magnification is needed to distinguish between the two species.  Bat bugs feed on bats and are found in homes with bats roosting.  Bat bug control requires preventing bats from roosting in the attic. Please see this article on bat exclusion.

Bed bug on the left - note the shorter hairs behind the eyes.  The bat bug on the right has longer body hairs.  Photo credit: Laura Jesse Iles, Iowa State University Plant & Insect Diagnostic Clinic.


Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on July 28, 2017. The information contained within may not be the most current and accurate depending on when it is accessed.