Evaluation of the efficacy and timing of molluscicide treatments



The aim of the trials was to provide independent information on comparative efficacy of slug control options such as ferric phosphate, a bio control agent (the nematode Phasmarhabditis hermaphrodita) and metaldehyde.


Two field trials were completed in each of two years using the cultivar Maris Piper. In the first year, the efficacy of programmes using metaldehyde, ferric phosphate and/or Phasmarhabditis hermaphrodita (NemaSlug) was evaluated. The three key timings for molluscicide application were:

  • just before the crop canopy meets;
  • around 4-5 weeks later (if rainfall/irrigation is present);
  • at burning down of the crop.

Applications of NemaSlug were timed to coincide with rainfall at early crop emergence, at tuber initiation (providing rainfall/irrigation is present at that time), and at burning down.

In the second year, NemaSlug was unavailable and the trials were used to assess if there is flexibility in the timing of molluscicide application in response to environmental conditions – primarily rainfall.


The results from the first year of trials demonstrated that it is possible to use ferric phosphate as an alternative to metaldehyde, and that both molluscicides deployed in a 3 treatment programme can provide effective slug management. Use of the slug biological control NemaSlug alone did not provide effective reductions in slug damage. However, an application of NemaSlug at burning down as part of a molluscicide programme was effective at reducing slug damage at one of the sites.

In the second year’s trials, a 3x molluscicide treatment programme was effective. This was based on an application just before the crop canopy meets across the rows, and at burning down as key timings, with a further timing in between those growth stages in response to a period of rainfall. The full details of the results are provided in the final report below.

Project code:
01 June 2015 - 31 March 2017
Project leader:
Andy Evans


111200025 Final Report