Upper Murrumbidgee Black Willows Survey 2006-07

Black willow (Salix nigra) is one of the most invasive willow species in the Upper Murrumbidgee catchment. Although programs have been previously undertaken, control can never be guaranteed to be 100% effective and on-going vigilance is required to ensure long-term control and avoid serious re-infestation. The most effective way to do this is to ensure that all landholders are aware of the problems and are able to identify black willows and understand how to control them at an early stage.

In a project supported by the NSW environmental Trust, willows on the Murrumbidgee River were surveyed in several stages by water-borne teams experienced in identifying and controlling willows, from the Willows Warriors Inc in two-man rafts. The water-borne approach appears to work well, as it reduces the logistics of access through private property, important in an area with a high number of absentee landowners. Landholders were notified in advance of the survey being undertaken, and media releases to local newspaper and radio helped to raise and maintain awareness of the project. Access through locked gates and absent landholders were the most frequently cited initial concerns about the project. Generally, consent was readily given when the landholder was advised that access would only be from the river.

Localised infestations of black willow were located in one pass of the river with trees to be treated in a second pass after gaining landholder consent and appropriate regulatory approvals.

Workshops were conducted to provide landholders with the necessary knowledge to identify and control willows. The Willow Warriors also offered to train landholders on-site with willow identification and control methods when undertaking the control stage. Disappointingly, this offer was not taken up by many landholders.

To continue to publicise the black willow problem, interpretive signs were developed for placement at strategic sites and venues.

Methodology/Approach

Surveying:

Willow Warriors Inc teams, in two-man rafts, surveyed the willows on stretches of Murrumbidgee River recording the following at regular intervals of about 200m, using best practice methodology recommended by the National Willows Taskforce:

  • location from GPS, left or right bank or mid-channel
  • photography, where relevant, to present infestations and assist with further identification
  • presence of willow sawfly infestation
  • willow infestation class (National Willows Taskforce classification)
  • whether the willows had been previously treated
  • number and size (age) of black, crack, golden, hybrid (crack/golden) and weeping willows.

This water-borne approach has enabled a rapid appraisal of the extent of black willow infestation, without the logistical problems of access through private property. As it turned out, it also facilitated landholder acceptance of the control, since the most common objection to control was from absentee owners being unwilling to provide access through private property.

Water-borne control approach is not entirely without problems – on one hand, low water levels make the survey slow and difficult, while on the other hand, local storms presented the opposite issue with sudden rises in water level requiring vigilance otherwise making control dangerous.

The Willow Warriors worked with the Duke of Edinburgh Awards scheme to engage youth in NRM. This served several objectives, including providing additional “spotters”, while introducing several young people to some of the more immediate issues of natural resource management through meeting landholders.