a rotten apple

a rotten apple

A person who negatively impacts an entire group of people through his or her words or actions. Taken from the proverb "a rotten apple spoils the bunch." Before you accuse the entire department of wrongdoing, you should try to find the rotten apple that initially caused the problem.
See also: apple, rotten
References in periodicals archive ?
19 ( ANI ): Manchester City striker Mario Balotelli is all set to join Italian giants AC Milan in a 24 million pound deal despite club owner Silvio Berlusconi branding him a rotten apple recently.
He is a rotten apple and could infect every group where he goes, even Milan.
The new poster asks: "Is there a rotten apple in the barrel?
London, Jan 9( ANI ): Former Italian prime minister and owner of seven-times European champions AC Milan, Silvio Berlusconi has branded Manchester City striker Mario Balotelli as a rotten apple after it was suggested the forward could make a return to San Siro.
Berlusconi said signing Balotelli was never in his mind, adding that the striker is a rotten apple that could affect every group of player where he goes including AC Milan.
Prandelli advised Balotelli to listen to Mancini's advice, and added that Berlusconi might have branded the striker as a rotten apple but he has always behaved nicely during national duties.
with help from an accomplice, needed surgery after slipping on a rotten apple while mowing the lawn and getting his foot caught in the mower.
He's bitter toward me because, I think, there are some third parties, a rotten apple, so to speak, that has manipulated him and turned him into this rotten apple's minion.
McDermott added: "Gullit said Alan Shearer was a rotten apple.
The front page has the heading "Is there a rotten apple in our barrel?
The poster asks: "Is there a rotten apple in the barrel?
A rotten apple is just an overly ripe apple, producing enough ethylene to "ripen" the rest of the apples in the barrel.