Plant and Insect Diagnostic Clinic Update - July 29, 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. 



Samples of cucumbers have increased in the last 2 weeks. We have confirmed fungal disease like Alternaria leaf spot and anthracnose, as well as vascular diseases such fusarium wilt. Management of foliar disease in the home garden and in commercial field requires a combination of sanitation practices, crop rotation, planting resistant varieties, reducing moisture by watering the crown of the plant (drip irrigation systems) as opposed of the foliage, and preventive fungicide sprays.


More information:


Cicada killer wasps have been causing worry across Iowa. These large wasps look intimidating, but they are not aggressive and stings are very uncommon. The female digs out a nest in the soil, often at the edges of sidewalks. See below for a picture of a cicada killer nest.  See the Clinic website for more information.

Lace bug damage is obvious on some of their favorite plants. I have noted damage on sycamore, oak and serviceberry.

A cucumber leaf with leaf spots. Includes microscopic views of Colletotrichum orbiculare.
Leaf spots on cucumber caused by the fungus Colletotrichum orbiculare.  Top right: Setae (fungal structures characteristic of this fungus);  Bottom right: close up of setae and conidia (spores of the fungal pathogen). Photo credit: Lina Rodriguez Salamanca, Plant & Insect Diagnostic Clinic.


Cicada killer nest, showing a big heap of dirt next to a cicada killer
Cicada killer wasp nests may be marked by a small pile of soil next to the opening.
Lace bug on a leaf
Adult lace bugs have an intricate, lace-like pattern of veins on the wings.
Leaf bleached by lace bugs
Lace bug feeding injury to sycamore leaves.
More leaves bleached by lace bugs
Lace bug feeding causes bleached stippling of the leaves.


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, ...

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, Horticulture and Home Pest News, 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 29, 2016. The information contained within may not be the most current and accurate depending on when it is accessed.