BUZZ-Ashtead and United Rentals fall as latter talks down May activity
** United Rentals (NYSE: URI - news) falls 7 pct after talking down May activity, according to traders
** Co speaking at KeyBanc Capital Markets on Thursday, according to Thomson Reuters data
** Top faller on S&P 500
** UK-listed peer Ashtead down 4.2 pct, moves to biggest loser on FTSE 100
** Second worst day for both stocks YTD
** Terex Corp down 7 pct, Oshkosh down 3.3 pct (RM (LSE: RM.L - news) : alasdair.pal.thomsonreuters.com@reuters.net)