For nearly 10 years, the contractors who trim trees for MidAmerican Energy Co. have avoided oaks between early spring and late summer because open, sap-flowing wounds encourage the spread of a potentially deadly fungal disease called oak wilt.

This year, MidAmerican decided to be even more cautious, adding 15 days to the blackout dates; contractors now try to avoid oaks between March 1 and Sept. 30.

Instead of trimming, they fill out paperwork noting the location and another crew returns during the months of October through February to do the job, said Bob Nelson, MidAmerican's district forester for the Quad-City area.

The winter months are considered safe because no sap is flowing and the small, sap-feeding beetles that spread oak wilt spores are not active then, he explained.

In instances when oaks need to be trimmed for safety or to maintain service, personnel seal the cuts made in the trees with latex paint to stop the flow of sap that attracts the beetles, he added.

These cautionary practices regarding oaks are applauded by arborists, foresters and plant pathologists who say the general public is not widely aware of oak wilt - how it can kill oak trees in months and how its spread can be contained simply by avoiding open wounds during high-risk months.

Not all tree companies inform their customers of the danger, arborists and foresters add. Either the companies themselves do not know about it or they do not want to risk losing a job.

Overall, oak wilt is not a huge problem in the Quad-Cities, but there are pockets here and there, including in Davenport's McClellan Heights and other old-oak areas.

In the Heights, some homeowners pay hefty sums to protect the 100-year-old trees that add so much to their property, both aesthetically and monetarily. As one woman said, "Our neighborhood depends on all these wonderful trees."

There had been some concern that oak wilt would increase in the Quad-Cities this year because of all the wounding that occurred with the straight-line winds that battered the region July 21, 2008. But Brian Jay of Davey Tree and Shrub Care in Bettendorf says he has not noticed any increase so far.

White vs. red

The mortality rate depends on the type of oak.

Red, black and pin oaks are most susceptible and can die within months; nothing can be done to save them.

White oaks, as well as bur, shinkapin and swamp oaks, are less susceptible and live longer once they get the disease. They also are more responsive to treatment, usually injections of a fungicide sold under the brand name Alamo (active ingredient Propiconazole), Jay says.

Treatments range in price from $250 to $600, depending upon the size of the tree, he explains, and they have to be applied every other year.

Mark Gleason, a plant pathologist at Iowa State University in Ames, says there has been no noticeable uptick in the disease statewide. The presumption is that because the disease is native to the Midwest, natural balances keep it in check. By contrast, when a disease or pathogen is introduced from another country, it can become an epidemic because there are no natural controls, he explained.

When oak wilt comes to a neighborhood and fells beloved shade trees, of course people think, "The roof is falling in," he adds.

As Keith Majors, the forester for the City of Davenport, says, "People don't pay attention to a problem until it affects them."