If I have to report my Australian work income (work and holiday visa) from 2018 in my Canadian tax return, will I be taxed on it? or have it exempt?

[TurboTaxLise]

Foreign income earned prior to arriving in Canada. We want to know about your World Income. 

You will not be taxed twice on your income from home, under the tax treaty Canada has with Australia, it is taxed at source. 

This answer link relates directly to your question and answers the taxation as well as the exemptions (review the links attached in the answer) to get a full understanding of how to enter this information on your Canadian tax return: s://bit.ly/2ttgDt0