A tough consumer market leads to plunging sales.A weak consumer environment is eating into sales at powersports vehicle manufacturer Polaris (PII -8.89%), and the company's stock is feeling the impact.Shares of Polaris traded down 10% as of 1 p.m. ET following a weak earnings report.A challenging retail environmentPolaris is a maker of off-road vehicles, boats, and motorcycles. The company posted third-quarter earnings of $0.73 per share on sales of $1.72 billion, falling short of Wall Street's $0.88 per sh ...