Plant and Insect Diagnostic Clinic Update - April 24, 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.




This week in the clinic we received several tomato samples with different disorders. The most important ones were related with inadequate pH and soluble salt content in the media (EC), hormonal disruption and oedema (blister like lesion as a result of biotic stressors.  See the image below.  Similarly we received Cuphia plants with intumescence symptoms(similar to oedema but intumescence occurs on the top side of the leaf while oedema typically occurs on the underside of leaves).


The pathogens of the week were Pythium causing root rot in annual ornamentals (Petunia) and a combination of Botrytis crown rot and fungus gnats in ornamental perennials (Lobelia). Remember that some perennials can be moisture-loving during the growing season, but the excess moisture can cause rot problems and ultimately kill plants over the winter. Fungus gnat larvae thrive in wet soil and can become a challenge to control.


We have received several evergreen samples with winter injury,  dieback/decline symptoms (spruce and white fir).




Ticks are common now with many samples being submitted.  Be aware when in grassy areas, woods and other good tick habitat.   Wear long sleeved shirts and pants and tuck pants into socks.  Repellants, such as DEET, can be used on the outside of clothing.  Remember ticks will be in grass or low growing brush and so are usually found climbing up your body (it is a myth that ticks drop from trees).  Remember to check yourself and children when returning home.  For more information on ticks common in Iowa please see ISU Extension publication PM 2036, Ticks and Tick-borne Diseases in Iowa.   


Edema symptoms on tomato foliage.Oedema symptoms on tomato foliage.


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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