Congrats Ned on the most appropriate reply.
Most appropriate reply? Really?
Had there been a simple tag with the photo saying "spraying gorse in New Zealand" and perhaps explaining that gorse is a problem there, I wouldn't have had to ask any questions.
As it is gorse in Wales is really a non-issue because our winter winds keep it in check. Last week though we did suffer gorse fires including one bad one on the Sychnant Pass, near Dwygyfylchi, Conwy, because as I am sure you know, gorse is highly flammable due to the oil contained in its branches.
The situation in New Zealand (for a non New Zealander) is not obvious because some weed control experts believe that spraying with a single application of herbicide is not effective and that combination methods of control are required. Moreover the situation in New Zealand is again less than straightforward because it was purposely introduced and has been found to provide ideal conditions for some of New Zealand's native seeds to germinate and grow. However over the past century it seems to have become a problem to be controlled.
So - you will forgive my inquisitiveness!! I like seeing helicopter images such as Ned's but I like it even better when I understand what's going on and why.