Vegetation management of greenspaces is emerging as a source of pesticide contamination to urban waterways. Glyphosate has been essential in many urban vegetation management programs, especially for the management of fence lines and other grassed edges. Pressure to move away from glyphosate has grown globally due to human and environmental health concerns. Alternatives are available, however, there are significant challenges in reconciling environmental, human health and commercial priorities when considering the alternatives.
We conducted a series of field and lab-based studies in collaboration with Greater Melbourne’s waterway management authority to identify if there are effective, safe and economically viable alternatives to glyphosate for the management of fence lines and other grassed edges, and what impact their adoption would have on program delivery and customer outcomes.
Non-chemical alternatives trialled (boiling water, brush cutting, edge mowing) were generally less effective and therefore required more frequent treatment. This was projected to substantially inflate annual program costs and delivery times and had the potential to compromise amenity and recreational values. Alternative herbicides trialled (bromacil, imazapyr, imazamox and imazapic), although effective, generally have narrower management uses than glyphosate which can lessen their desirability as a program tool. Imazapyr was effective and has potentially broad management uses but is slower to produce outcomes and requires considered application to control non-target impacts to nearby vegetation. Bromacil provided effective control in some areas, but outcomes were inconsistent between sites. Although limited in its potential applications, bromacil could provide an alternative in some contexts.
Using these studies as an example, we discuss the opportunities and challenges for eliminating or reducing glyphosate use in a large-scale vegetation management program. We present potential solutions to reduce reliance through the adoption of complementary control methods and simple integrative strategies. These approaches will support managers to reconcile environmental, safety and commercial priorities.