Frequently asked questions

news updated: 18 May 2009

How can the Fringe Lily be controlled?

---2006 to 2010

Over the last five spraying seasons members of the Lochmaben Initiative in conjunction with Scottish Natural Heritage (SNH)have undertaken 17 spraying sessions on the loch (2 in 2006, 6 in 2007, 2 in 2008, 3 in 2009 and 4 in 2010). The spraying had a dramatic impact on the lily which died off soon after being treated. Despite this initially encouraging result, in 2007 the lily was found to have regenerated in those areas which were sprayed in 2006. This trend has been seen many times over the last decade and is expected to occur again next year on those areas that were sprayed this summer. The map shows the 2007 extent of the lily. Inclement weather--wind and rain--resulted in only 2 effective spraying sessions in summer 2008, 3 in 2009 and 4 in 2010.

The lily is continuing to spread and there is now a new area along the north western shore. It is a concern as that the chemical currently being used, glyphosate, is not providing effective control. This was confirmed recently by the Centre for Aquatic Plant Management (CAPM) who tested the use of glyphosate on the lily and concluded that it cannot be relied upon to provide effective control.

As a result of observation and through discussion with freshwater experts from SNH and CAPM, a different approach is was tried. In March 2008, a trial of a different chemical, dichlobenil was carried out. Dichlobenil comes in a granule form and is scattered into the water where it sinks to the bottom and is taken into the plant through its roots. This method kills the plant from the root up as opposed to from the leaf down, as in the case of glyphosate. Research undertaken by CAPM shows this to be significantly more effective in controlling the lily.

Dichlobenil is a more powerful chemical which is likely to impact on other plant species, is moderately toxic to fish, water flea, and algae, and has a half life of approximately 2.8 years. This mean that is potentency reduces by half in that time.

It is felt that this is an acceptable risk as the alternatives i.e. continue to use glyphosate, or do nothing, is likely to result in the continuing spread of the lily until it reaches a point where it will cover about 25% of the loch surface (see map) This will result in impacts on other plant species and perhaps some of the birds and insects too. Additionally, recreational activities such as fishing may become be severely restricted. The trial of dichlobenil covered an area of approximately 10m x 50m in the north and a further trial area similar in size in the north-west will have four sections—glysophate + sticking agent; dichlobenil; control area; glysophate. Buoys and stakes marked the limits but tragically these were removed by people in a boat.

For the remaining areas of the loch it is intended to continue to use a glyphosate solution but one with a new soya based sticking agent added.
When sprayed onto the leaves of the lily, the solution adheres to the leaf surface and slowly releases the glyphosate. Research shows that it can significantly improve the effectiveness of glyphosate as it isn’t getting washed off the leaves. The agent is completely non-toxic and proved successful in the areas it was used.

Unfortunately weather conditions in 2008 did not aid an extensive spread of dichlobenil but the areas covered were quite distinctive re the absence of the fringe lily. In April 2009 the Initiative got the use of the Wheelie Boat from the Castle Loch and in one day managed to cover a greater area than before and did make an impact on the area of lily seen in July. The least impact was in the south west and north west corners. European Law means that no more dichlobenil can be spread on the loch. As the weather in July was either wet or windy or both, no spraying was possible. Two sessions were completed in August using the glysophate + sticking agent and the result is that the lily for the first time for a decade was absent from most of the loch except for the north west. The following photographs show the southern bay at the end of the Vendace Drive houses, the first taken in September 2008 and the second in September 2009. They illustrate the progress made in 2009 despite the fickle weather.

It is of concern that the weather pattern of regular wind and rain in June to August in the past 3 years has restricted the opportunities to spray the lily. The Initiative has agreed to operate again in 2011 but the team is getting older and there needs to be a meeting with SNH to discuss the future management control of the lily. If no action is taken, the lily will repopulate the Mill Loch.

The continued growth of the lily also poses a risk to Castle Loch. If fragments of the lily escape from the Mill loch and enter the Castle Loch, it could have very serious implications.
The Mill loch forms part of the Lochmaben Lochs SSSI and is noted for its open water habitat, its areas of open water/fen transition, and its invertebrates. The aim of SNH is to maintain these features and return the loch to as natural an area as possible.

Further information on the SNH site.

View a map of the coverage of the loch by the lily in 2007

View a map of the coverage of the loch by the lily in 2009

View a map of the possible coverage of the loch by the lily if left to spread.