Toyota Motor Sales U.S.A. Inc.’s August sales fell 31.4% vs. August 2009, when the U.S. “Cash-for-Clunkers” scheme was active.

Last month’s falloff was Toyota’s biggest monthly U.S. vehicle sales drop since June 2009’s 34.4%, according to Ward’s data.

Not surprisingly, passenger cars were among Toyota’s poorest performers last month, such as the Camry and Corolla, its best-sellers under the Cash for Clunkers buyer-incentive program.

Non-hybrid Camry sales fell 41.2% in August, the Camry Hybrid slipped 42.7% and Corolla deliveries were down 49.9%.

Also hard-hit by the year-ago comparison were the Prius hybrid – another Clunkers standout – the Yaris subcompact and Highlander Hybrid cross/utility vehicle. Their August sales plummeted 35%, 37.1% and 39.5%, respectively.

“At first glance the August numbers don’t look very pretty, but we’re characterizing August as a fair month for Toyota,” Bob Carter, group vice president and general manager, tells media during a conference call.

Carter dismisses the year-ago comparison as “not relevant” because of the government-sponsored trade-in program.

In positive territory for the core brand were the Avalon large sedan, up 17.3%, and the 4Runner and FJ Cruiser utility vehicles, both up by triple-digit percentages.

The Tundra fullsize pickup truck posted a 5.0% decline and the RAV4 CUV slipped 16.4% vs. year-ago.

The Lexus RX 350 CUV also was a popular choice among Clunkers program participants who received up to $4,500 for trading in older, fuel-thirsty vehicles. Its sales slipped 1.9%.

Lexus Div.’s performance was mixed in August. Sales of passenger cars fell 22.9%, but light trucks rose 2.3%. Mark Templin, Lexus group vice president and general manager, says the luxury brand was hurt by the tough year-over-year comparison, as it was the top-selling luxury brand under Cash for Clunkers.

The best-performing Lexus in August was the new GX 470 SUV. Its sales soared 78.2%.

Toyota’s Scion lineup continues to underwhelm, with sales of all three of the brand’s models off more than 55% from year-ago.

Carter says Toyota is recovering from negative publicity surrounding high-profile recalls earlier this year. He cites a 57% trade-in rate by owners of competitive makes, a level not seen since last year.

Carter says Toyota will extend through September its 2-year free maintenance promotion instituted after the recalls. It was scheduled to end Labor Day.

The lasting impact of the recalls “is something we review every day,” he says, adding a greater concern to Toyota now is the struggling U.S. economy.

He says fleet sales accounted for 6% of Toyota’s August sales. Several auto makers, notably the domestics, have been criticized for leaning on fleet this year as retail sales soured.