US SMALL/MIDCAPS-Stocks drop; LSB issues negative outlook

NEW YORK, Oct 12 (Reuters) - Small- and mid-capitalization stocks fell o n Friday and underperformed larger caps, with shares of LSB Industries falling after it warned on third-quarter results.

Shares of the chemical products maker closed down 8 percent at $39.91 after it said third-quarter results were "adversely affected" by lower-than-expected production at its main ammonia plant.

A number of U.S. companies issuing negative forecasts for the third quarter has increased investor concerns about the impact of slower global growth on corporate America.

Earnings in the large-cap arena began this week with results from Alcoa after the bell on Tuesday. The bulk of results from smaller-cap companies will soon begin in earnest.

"I think we are likely to see a softer (earnings) season than what we've seen in the last quarter. I don't think we're going to see a great deal of positive surprises," said Natalie Trunow, chief investment officer of equities at Calvert Investment Management in Bethesda, Maryland, whose firm manages about $13 billion in assets.

The S&P MidCap 400 index was down 0.7 percent while the S&P SmallCap 600 index was down 0.9 percent. In comparison, the benchmark S&P 500 ended down 0.3 percent.

(Reporting By Caroline Valetkevitch; Editing by Diane Craft)

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