The slug retrospective

Intriguing article by RHS entomologist Dr Hayley Jones, shedding light on the little-known benefits slugs to (garden) ecosystems.

Slug crawling on the ground

Slugs play valuable roles in our gardens and ecosystems, and the number of slugs that are ‘pest species’ for garden plants is actually low in proportion to the wide array of fascinating slugs found in the UK.

Admittedly, rarely having attempted to do so but slugs are apparently very difficult to identify and in some cases can only be distinguished through dissection. In her compelling article, the RHS entomologist Dr Hayley Jones, provides a run down of slugs and means to identify which family a slug belongs to. Valuable information for all to understand which ones pose a threat to prized plants and which are there to help decompose organic matter in gardens.

Slug identification can be done from the position of the breathing pore, whether or not it has a mucus pore, and the pattern of wrinkles on the mantle (section between head and tail). To highlight their ecological value in her article, Jones presents slugs in three main categories:

  1. The plant munchers: Evident by their name, these are the culprits that fancy prized hostas, young lettuces and leafy treats in gardens. According to Jones there is no effective or sustainable way to get rid of slugs, which means that the best approach to combat the plant munchers is to encourage natural predators by ensuring a healthy and balanced ecosystem in the garden. Jones presents examples of plant munching slugs such as the grey, large black and the tramp slug.
  2. The good guys: According to Jones, the majority of slugs are valuable garden recyclers, grazing on algae, fungi and detritus. Many species feed on decomposing organic matter, such as dead leaves, dung, and even dead animals – hence a valuable part of the garden’s ecosystem. Often spotted, the leopard slug, for example says Jones, doesn’t pose a threat to your plants. Leopard slugs are highly territorial and actually scare off other slugs. As a ‘guard slug’ therefore, they are a friend to the gardener rather than a foe. Included in this group are the green slug and orange or golden shelled slug.
  3. The cool ones: Only an entomologist can come up with this classification, but she’s winning us over. Jones highlights species such as the ash black slug, a woodland species which can grow up to 30cm long and is valued indicator of ancient woodland. Another is the native shelled slug, which apparently does indeed have a shell (yet is not a snail) and lives almost entirely underground, is carnivorous and feeds on worms.

A definite worth a read article, especially as slugs and snails are very much part of the garden’s ecosystem and it’s time we respect their valuable contribution. The article includes a video to help with slugs identification if Jones has inspired slug curiosity and a fact sheet including fun slug facts.

“Slugs are one of the many things that stops everything lying around dead all the time”, explains Dr Hayley Jones, RHS entomologist. Jones leads RHS research into slugs and snails (gastropods) in gardens while also working on the agapanthus gall midge, a new pest to science, discovered by the RHS in 2014.