Plant and Insect Diagnostic Clinic Update - July 10, 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.


Earwigs continue to annoy homeowners and gardeners.  Earwigs under the loose bark of trees are hanging out in a moist location to feed on fungi and decaying organic matter.  They are NOT the cause of the loose bark or tree decline.  In other words, if your tree has trouble the earwigs are not the problem – they are innocent bystanders taking advantage of an existing situation.  More about earwigs on the Clinic website.  


Diseases of interest the past two weeks have included raspberry leaf spot, maple anthracnose, needle cast and tip blight on various conifers, nutritional deficiencies and Fusarium wilt of tomatoes.

Raspberry leaf spot: Gray or white lesions with a well-defined margin characterize this disease. To prevent it, promote air circulation within planting and row. These practices include weed control, proper spacing, and pruning practices. Prune old infected material after harvest and remove from the field. This can help decrease the amount of fungus that could infect canes next season. See pruning guidelines in ISU Extension & Outreach pamphlet PM0780, Pruning and Training Fruit Trees.

More information on raspberry leaf spot is in the Horticulture & Home Pest Newsletter (HHPN) for September 28, 2011.

For general raspberry culture see Proper Care of Raspberries in HHPN from April 14, 1993.

Pin oak iron deficiency is common this year. The excessive soil moisture due to rains can result in stressed trees, as soil conditions become conducive to nutrient deficiencies. For more information see the Michigan State University Extension News for June 12, 2013.

Fusarium wilt of tomatoes: Drooping and wilting leaves, and yellowing of the lower portion of the foliage are typical symptoms of Fusarium wilt of tomatoes. Fusarium wilt is caused by the fungal pathogen Fusarium oxysporum. This pathogen lives in the soil and can remain in a given field for many years. Management tactics can be found in Ohio State University Extension Fact Sheet 3000/3122.

Our curiosity of the week is a mushroom known as White Dunce Cap Conocybe latea.  It is common in lawns, baseball fields, and grassy areas and is named for the narrow conical shape that resembles a dunce cap.  See the MushroomExpert.Com for more information.

The dunce cap mushroom is common in lawns and other turfgrass areas.

The dunce cap mushroom is common in lawns and other turfgrass areas.


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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