* Organic sales up 3.7 pct, weakest growth since 2009
* Russell Stover business still struggling
* Shares down nearly 2 percent (Rewrites, adding analysts, share price reaction)
ZURICH, Jan 16 (Reuters) - Swiss chocolate maker Lindt & Spruengli reported its weakest sales growth in nearly a decade on Tuesday, hurt by ongoing problems at its Russell Stover business.
The group's shares fell nearly two percent in early trading after it missed its own long-term target and the average of analyst estimates, chiefly due to a sales drop in North America driven by a decline at Russell Stover, the maker of chocolate assortment boxes.
Lindt's 2017 organic sales growth slipped to 3.7 percent from 6 percent a year earlier, its lowest level since 2009.
Some analysts said they were concerned about the lack of a new efficiency plan to deal with the downturn, and added that the company's long-term growth target of 6 to 8 percent could be under threat.
"Lindt's premium valuation is built on the back of its strong organic sales growth, mostly in mature markets in whatever conditions. Denting that reputation is likely to dent the multiple," said Jon Cox, an analyst at Kepler Cheuvreux.
Lindt, known for its gold foil-wrapped chocolate bunnies, trades at nearly 40 times earnings while members of the Stoxx 600 Food and Beverage Index trade at 25 times, Reuters data show.
Lindt's organic sales increase lagged the Reuters poll average of 4.2 percent.
But a stronger euro helped annual sales rise by 4.8 percent in Swiss francs to 4.09 billion Swiss francs ($4.24 billion).
The group based in Kilchberg on Lake Zurich will report full earnings on March 6.
It kept its outlook for 6-8 percent organic sales growth and increasing margins by 20-40 basis points.
"Given the deteriorating trend ... we believe more investors might start to question the achievability of that target going forward," said Helvea analyst Andreas von Arx.
"Whereas Nestle and Unilever execute in portfolio-improving deals, Lindt's key step has been the expensive, non-delivering Russell Stover acquisition."
Chocolate confectionery demand was sluggish last year as consumers often preferred healthier snacks, but Lindt has overcome the trend thanks to its positioning in the faster-growing premium price segment. Lindt said organic sales in Europe rose 6.2 percent and by 12.4 percent in the rest of the world.
But North America remained a headache, with sales falling 1.6 percent in the market where Lindt advanced to the number three position in chocolate with its Russell Stover buy in 2014.
Russell Stover, the maker of Whitman's Sampler boxes of chocolates, struggled amid a weaker market in general and difficulties experienced by some of its retailers, including drug stores and department stores, Lindt said.
Lindt has been trimming Russell Stover's product lineup and cutting back on unprofitable promotions as it aims to turn around the business. It said the overhaul was "progressing."
($1 = 0.9637 Swiss francs) (Editing by Michael Shields)