By DOUG SCHMITZ
Iowa Correspondent

IOWA CITY, Iowa — Severe thunderstorms that rolled across the Midwest early  on July 11 created derecho winds that exceeded 100 miles per hour, according to state agronomists surveying widespread damage to fields in their areas.

“I never thought I’d live to see a storm that rivals the 1998 storm that had 100 mile per hour winds in a 20-mile swath over 100 miles long,” said Jim Fawcett, Iowa State University extension field agronomist for eastern Iowa.
“But the storm Monday morning, July 11, apparently had straight-line winds of up to 120 miles per hour in a swath of 20 miles or so wide, and traveled from south of Ames up through Tama, Benton, Linn and Jones counties and into Dubuque County.

The thunderstorms carved a destructive path through central, eastern and northeastern Iowa, on into northern Illinois, southern Wisconsin and parts of Michigan, toppling trees, leveling buildings, destroying livestock and minimally green-snapping corn. Mark Licht, ISU extension field agronomist for central Iowa, said wind damage to corn started north of Woodward and moved east through Slater, Huxley, State Center, Marshalltown and eastward.

“I’ve heard reports that the damage was eight miles wide in several areas,” he said. “From what I’ve seen at this early stage is mostly lodged corn to within a foot of the ground and some slight green snap,” or the breakage of corn stalks caused by high winds primarily during the elongation (or rapid growth) period.
In fact, in Iowa alone, Fawcett said there’s likely more than 100,000 acres of corn flattened, in addition to thousands of trees snapped off, grain bins blown over and farm buildings destroyed. Moreover, winds leveled corn in the worst-affected areas to less than knee-high, said Roger Elmore, ISU extension corn specialist and professor of agronomy.

“This follows glowing reports of how well the crop looked – before the wind came along,” he said. “The lodging was not likely related to corn rootworm feeding.”

But Fawcett said the good news is “it looks like the vast majority of the corn is flat because of root lodging and not green snap” in his seven-county area. “I’ve looked at fields from Martelle in Jones County over through Vinton to Toledo, and every flattened field I looked at had very little green snap,” he said last week.

Last Thursday, Fawcett held an impromptu meeting at the John Olson farm south of Vinton – a town of more than 5,200 residents which received extensive property damage and power outages – to discuss the damage to crops with area farmers.

“With the 1998 storm, there was a tremendous amount of green snap, which resulted in large yield losses,” he said. “The 1998 storm occurred on June 29, so much more of the corn was in the more vulnerable V10 to V12 stage, when stalks are more brittle. Most of the corn is in the V14 to V18 stage now, so less subject to green snap.”

The heavy downpours that occurred at the same time, Fawcett added, may have also helped by saturating the topsoil and allowing roots to shift rather than breaking stalks.

“In general, the lodging is not as extensive in the seed fields, because the corn is shorter, but unfortunately, there are many seed fields where the lodging is great enough so that it is difficult to impossible to walk through the fields,” he said. “This means they cannot be detasseled, so they are a total loss. Many seed fields may be disked up.”

Elmore said regarding yield reductions caused by the winds in large seed production areas, “rogueing, detasseling, field inspection and other operations will be dramatically affected because of the disruption in the canopy, including position of the female rows and their orientation.”

John Holmes, ISU extension field agronomist in Clarion, said farmers in Tama and Marshall counties, as well as southern Hardin County, had experienced severe lodging, with much of their corn just 2-3 days from tasseling. “The lodging was reported to be more severe in corn that was seven to 10 days away from tasseling,” he said.

In northern Illinois, damaging winds have been wreaking havoc over the past two weeks on many of the state’s cornfields, where green snap and root lodging have occurred, according to Emerson Nafziger, University of Illinois extension agronomist in Urbana.

“It’s not a rare phenomenon, but we seldom have large acreages affected by green snap,” he said. “It’s not at all uncommon to find fields with the same hybrid, planted a few days apart, showing different levels of the problem.”
But Virgil Schmitt, ISU extension field agronomist in southeastern Iowa, said the stalks will eventually straighten back out (or at least the upper stalk will straighten), “so hopefully, there will not be a large effect on pollination.”
In southwestern Michigan, the severe line of thunderstorms that caused significant damage disrupted the hot and dry conditions that followed the Fourth of July weekend, said Bruce Mackellar, Michigan State University extension agronomist.

“Straight-line winds up to 85 miles per hour with reports of possible tornadoes and driving rains caused a lot of trees to fall on structures, widespread power outages and some crop damage,” he said, “particularly to the area’s tart cherry crop, which was just about to be harvested.”

In the interim, Schmitt said farmers should contact their crop insurance representatives since some policies may not cover storm damage to crops. They should also start planning for a difficult harvest, he added.