What Insurance Is Needed For Casual Outside Workers?

We live on acreage in Brisbane and need quite a lot of outside work done. Things like brushcutting, weed spraying, gardening, scrub clearing etc We would supply tools and materials etc so the job would suit an unemployed person or a student. What if they are hurt in some way while doing the work? Do we need to take out insurance for them? If so, what type of insurance is it and who should we get it from? I’m pretty sure that normal workers compensation insurance doesn’t apply to workers who are employed by householders.