bungle, blunder, overlook, confound, misconduct, fumble, mess up*, foul up*, kill the goose that lays the golden eggs*, bark up the wrong tree*; see also fail 1.
"mismanage." YourDictionary, n.d. Web. 16 May 2018. <http://thesaurus.yourdictionary.com/Mismanage>.
mismanage. (n.d.). Retrieved May 16th, 2018, from http://thesaurus.yourdictionary.com/Mismanage
To harm irreparably through inept handling; make a mess: