AMES, Iowa – During the summer, diagnosticians at the Iowa State University Extension Plant and Insect Diagnostic Clinic help Iowans diagnose and manage diseases on their plants and identify insects that might be the source of problems. But during the winter they keep busy — even when the bugs aren’t.

Diagnostician Christine Engelbrecht said researching summer diseases during the winter keeps them up-to-date with disease management recommendations to keep plants healthy.

A recent project Engelbrecht said she was working on is researching the causes behind the loss of leaves on bur oaks in the middle of summer.

“Even though it’s a disease we’ve been seeing in the summer, we’ve still been working on it,” she said. “We’ve been doing genetic analysis. It’s just one of the fun projects we get to work on during the winter.”

Engelbrecht said this is a special project because the fungus is normally found on red oaks, not bur oaks. Her research has shown the pathogen is genetically different on the two trees— perhaps requiring a different approach to managing the disease.

She said managing this one is difficult because fungi and bacteria are the cause of most diseases. Hundreds of fungi and bacteria live on the plant harmlessly or only eat the dead tissue after the plant gets sick.

An example of this is sudden needle drop that recently has been appearing in Iowa on spruce trees.

Engelbrecht said this new disease was first found in Wisconsin, Minnesota, Kansas and Missouri. Its symptoms include the sudden yellowing and dropping of needles on scattered branches of the spruce, starting on the base of the tree and often leaving the newest needles intact at the end of the branch.

“Its kind of unusual because it affects Norway spruce, blue spruce and white spruce so it’s pretty broad in its host range,” Engelbrecht said.

She said there is a fungus that they consistently find on the infected trees but they aren’t entirely certain that it is the source of the problem.

For more information, contact the clinic by phone at (515) 294-0581, e-mail sickplant@iastate.edu or send a sample to Plant and Insect Diagnostic Clinic, 327 Bessey Hall, Ames, IA  50011. Also check the clinic’s Web site, http://www.plantpath.iastate.edu/pdc/.

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