Plant and Insect Diagnostic Clinic Update - September 12, 2012

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


A sample of spruce gall adelgid was an unusual one.  They occur in Iowa, but we only get a sample once every few years. 

We received a sample of a pin oak heavily infested with insect galls (see photo below).  The female lays her eggs on the emerging leaves in the spring. The egg laying and larval feeding causes the plant to form the gall tissue around the insect. The galls look strange but are actually plant cells. The larvae can then feed safely inside the gall.  Leaf galls do not normally cause the health of the tree and there are no practical controls for leaf galls.  Leaf galls are commonly caused by wasps, midges or mites.


Small oak apple galls on the leaf of a pin oak.



A lot of bur oak blight samples coming in. A couple of bur oaks have also come in with oak wilt symptoms.

We’ve also seen some white pines with brown needles, most likely due to environmental or site conditions.

A honey locust sample was diagnosed with a leaf spot disease caused by a fungus called Linospora sp. This disease is more common in the southern United States and it’s the first time we’ve seen it in the clinic.

We also received an apple sample with cedar-apple rust lesions.

Honey locust leaf spotHoney locust leaf spot


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