Addressing a press conference in Nelspruit, Mahlangu said the ANCYL would do everything in its power to make sure that Cope does not get any seats in the provincial legislature in the forthcoming general elections.
There are only 30 seats in the Mpumalanga legislature and Mahlangu insisted that the ANC would get 29 of those seats.
"The other seat will go to any opposition party, but not Cope. We will surrender this seat only because the Independent Electoral Commission’s (IEC) method of counting votes has a thing called fractions.
"However, not one of those mad dogs who defected from the ANC and formed the Assembly of Polokwane Losers should get anything. We will spray these insects with Doom," said Mahlangu.
Mahlangu said "everyone knows that Cope was formed by insects that are hell-bent on holding onto power".
He said the ANCYL would mobilise thorough door-to-door campaigns across the province to ensure no one votes for Cope.
"This way they will not get a seat in the legislature and will perish like Bantu Holomisa's United Democratic Movement (UDM)," he said.
Cope 'will surprise the ANC'
Buks Mahlangu, Cope spokesperson in Mpumalanga, said they will not blow their own whistle, but will surprise the ANC and its youth league in terms of seats won in the provincial legislature.
"Let the youth league spread its propaganda, but the people will decide if we have a seat or not. We have branches in almost all the villages in this province and there is a possibility that we might surprise them and take more than half of the seats in the legislature," said Mahlangu on Wednesday.
He said he does not understand why the ANCYL is "making noise" about a party that was only launched recently, "unless they are threatened by it".
"We are not threatened by the ANC. Why can't they make noise about other opposition parties, not only Cope. Maybe this means they are the ones who feel threatened," he said.
Recently James Nkambule, the man who publicly accused Mathews Phosa, Tokyo Sexwale and Cyril Ramaphosa of plotting to oust former state president Thabo Mbeki in 2001, defected from the ANC to join Cope.
Nkambule, former secretary of the ANC Youth League in Mpumalanga, announced his defection at a Cope meeting in Barberton on February 1, saying that the ANC he loved and supported had "died at the 52nd ANC Congress in Polokwane in December 2007 when Mbeki was unceremoniously removed from office".
"Yes, I have joined Cope," he confirmed. "How can I remain a member of the ANC when the movement has lost the plot and is allowing radicals like (ANCYL president) Julius Malema to shoot their mouths off."
Referring to ANC president Jacob Zuma's long legal battle against corruption charges, Nkambule said the ANC he joined would never have allowed one man's problems to become the nation's problems.