Monitoring

Monitoring

Regardless of the weed control option chosen, it is important to monitor the results of control actions. Monitoring answers the key question of whether the desired outcomes are being achieved.

The first step in this process is to record vegetation distribution and abundance in the water body or waterway befoe any weed control option is undertaken, so as to establish “before treatment” conditions. Repeat observations following weed control will enable the changes in target and non-target vegetation to be assessed. Where necessary, control actions can then be modified and improved to ensure better control or to minimise adverse environmental impacts.

The specific monitoring practices employed are largely dependent on the site and type of weed control programme. For deeper lakes scuba divers may be needed to record vegetation along lake profiles (the species present, their height and cover). Water quality and other aquatic life may also need to be monitored.

The importance of tailoring a monitoring programme for a specific weed problem and control strategy cannot be underestimated. For example, Lake Eland became a grass carp trial site for the eradication of hydrilla in the late 1980s. An eradication programme necessitates the highest level of monitoring and the monitoring programme for this lake continues today with an annual extensive survey of the lake by scuba divers looking for hydrilla plants and propagules. Today the weed beds have gone, but few small plants remain. If less stringent monitoring had been undertaken, some of these plants may not have been found, which may have led to inappropriate conclusions being drawn as to the effectiveness of grass carp to eradicate hydrilla.

Find out more about using grass carp to eradicate hydrilla

Revised October 2002