In many cases, there is a need to control invasive species such as Japanese knotweed and giant hogweed. Removal might be required to protect human health, ensure infrastructure is not damaged or, in the case of some invasive species, there is a legal requirement to remove them.
Pesticides are the main tool of choice for killing invasive species, and, unlike with other unwanted vegetation, there are currently limited cost-effective alternatives available. However, this is slowly changing as more non-chemical alternatives are being developed. In the meantime, councils seeking to go pesticide-free can build an exemption clause into their policy permitting them to use herbicides for the purpose of controlling invasive species. However, they should use techniques that keep the amount of pesticides used to a minimum, such as injecting the chemical directly into the stem of the plant thereby reducing runoff and drift. They should also monitor developments in alternative treatments and be open to trialling them as they come on to the market.
It should be noted that councils only using pesticides to tackle invasive species are likely to be using far lower amounts than those using them to maintain whole areas such as parks and pavements.