June 26 (Bloomberg) -- Oshkosh Corp., the Wisconsin-based maker of aerial work platforms, fell the most in 22 years after saying it will post a third-quarter loss on an acquisition- related writedown and lower sales in North America and Europe.

Oshkosh declined $11.22, or 33 percent, to $22.29 at 4:04 p.m. in New York Stock Exchange composite trading, the largest percentage decline since its initial public offering in October 1985. The news pulled down shares of other construction equipment makers including Terex Corp., which fell the most in more than five months.

Oshkosh said today in a statement it now forecasts a loss of as much as $1.32 a share in the third quarter, compared with its prior forecast of profit as much as $1.50. The average of 11 analyst estimates compiled by Bloomberg was for profit of $1.44 a share.

``The revised outlook reflects lower-than-expected sales in both North America and Europe, including soft non-residential construction trends,'' wrote Seth Weber, an analyst with Banc of America Securities in New York.

The news may have ``negative implications for Terex,'' Weber said. Weber has a ``neutral'' rating on Oshkosh and recommends buying Terex, which he described as ``direct aerials competitor'' to Oshkosh.

The Standard and Poor's 500 Construction & Farm Machinery Index, which includes Caterpillar Inc. and Terex, fell 4.6 percent, the biggest decline since Feb. 5.

Garbage Trucks

Oshkosh will record an impairment to goodwill of about $175 million, or $2.32 a share, from its purchase of Geesink Norba Group, a European garbage truck-maker, the Oshkosh-based company said. The writedown was necessary because Geesink faces ``a slower and more difficult than expected return to profitability,'' as well as a weaker European economy and higher raw materials costs, the statement said.

The third-quarter forecast also reflects lower orders for aerial work platforms used in non-residential construction, which has slowed in North America and Western Europe, Chief Executive Officer Robert Bohn said on a conference call today.

Some of Oshkosh's large customers have told the company ``they plan to significantly reduce their capital spending for the remainder of this year,'' Bohn said.

Caterpillar, the world's largest maker of construction equipment, fell $2.30, or 3 percent, to $74.28. Komatsu Ltd. is the No. 2 machinery manufacturer.

To contact the reporter on this story: Edmond Lococo in Boston at elococo@bloomberg.net; Courtney Dentch in New York at cdentch1@bloomberg.net.

Last Updated: June 26, 2008 16:24 EDT