Eighteen brokerages, including Barclays Capital, Mizuho Securities USA, Credit Suisse, Raymond James, Robert W. Baird & Co and Canaccord Genuity, cut their price targets on the stock by an average $132 to $612.
Apple's shares slid to $451 at the open on the Nasdaq.
Jefferies & Co cut its rating on Apple's stock to "hold" from "buy" and slashed its share price target by $300 to $500.
Jefferies analyst Peter Misek, who has previously raised red flags about Apple cutting orders to suppliers, said the iPhone slowdown was "real and material" and here to stay.
"We think Apple is losing the screen-size wars," Misek said, noting that demand was moving away from the iPhone's 3.5-inch and 4-inch screens to screens of 5 inches offered by rivals such as Samsung Electronics, HTC and Nokia Oyj.
Misek is a top-rated analyst for the accuracy of his earnings estimates for Apple, according to Thomson Reuters StarMine.
Apple said it shipped a record 47.8 million iPhones in the December quarter, but this lagged the average analyst forecast of 50 million units.
Deutsche Bank trimmed its price target to $575 from $800, and said Apple should start making a lower-priced iPhone to arrest the market share loss.
Expectations heading into the results had been subdued by news of possible production cutbacks, hitting a stock that hit a life high of $705.07 just four months ago after the launch of the iPhone 5. Since then, Apple's shares have dropped 35 percent.
NEW PRODUCTS NEEDED
Analysts said the company's growth would hinge on new products, but added that a new launch wasn't on the horizon.
"To re-accelerate growth, Apple likely needs to launch new products, yet few seem likely before June," Nomura's Stuart Jeffrey said.
The company has been long rumored to be working on a television but has so far deflected questions on its existence. Apple hasn't launched a new line of products in almost three years, apart from a smaller version of the iPad.
Some analysts questioned the company's strategy of betting its fortunes on one phone, while others said a cheaper iPhone could arrest market share loss.
"Apple's modus operandi to date has been to cream the high-end off each market, but as the company's grown it may now need to target more of the mainstream," Evercore Partners analysts said.
Up to Wednesday, 24 analysts had lowered their price targets since October when Apple reported its fourth-quarter results, according to Thomson Reuters data.
Apple is the lowest ranked stock among the marquee technology firms in the United States based on the change in analyst sentiment, or Analysts Revision Model (ARM), according to StarMine.
Apple's global ARM score of 10 is well below Google Inc's 34 and Microsoft Corp's 19 out of a possible 100. Nokia and Samsung have scores of 82 and 89, respectively.
Research in Motion has a perfect score of 100, according to the model, which measures analysts' revision of key indicators such as earnings and revenue estimates and changes to their ratings.
Copyright @ Thomson Reuters 2012