- Potatoes are attacked by three main genera of slugs, which breed at different times of the year with the result that at any time of the season there may be eggs, immature and mature slugs within a crop.
- Slugs will feed on above and below ground parts of potato plants, economic damage occurring when tubers are “holed” by feeding slugs.
- Slugs prefer to remain under shelter, such as a crop canopy or the soil surface, which prevents loss of water from the body.
- Slugs do not burrow through soil but move under clods or in cracks, crops grown in such soils are therefore more susceptible to slug damage.
- Slugs which have been feeding underground are most likely to come to the surface in cool, moist conditions such as at night or after rainfall.
- Potato tubers become most susceptible to slug damage late in the season and when the skins have set.
- Some slug species can remain active at temperatures little above freezing, so control may be required throughout the year.
- As slug eggs may be present throughout the year these can help to maintain slug populations.
- For descriptions of the main pest species of slugs in potatoes see: Slug notes.
- A Slugs identification guide can also be found via this external link.
Assessing populations of slugs and caribid beetles (slug predator)
- Slug populations may be assessed most effectively by examining fields at night, particularly after rain.
- Caribid beetles are effective predators of slugs and their populations may be assessed by placing pitfall traps between the potato rows.
- Cloddy soil and crop debris before a potato crop can encourage slugs, so control should start with harvest of the previous crop.
- Cultivate land to achieve a fine tilth in the ridge and so restrict mobility of slugs.
- If there are wet, cloddy areas within a field, where control of slugs is particularly difficult, it may be necessary to avoid planting these areas, particularly if growing for a “quality” market, where a small proportion of “holed” tubers may make a sample unacceptable.
- Harvest early or green top; avoid leaving tubers in the ground after skins have set, particularly late in the season.
- If carabid beetles are present, refuges placed between the rows may provide shelter for beetles and so increase their efficacy.
- Biological control can be provided by application of specific nematodes (“Nemaslug”) which are predators of slugs but the costs and application requirements do not generally make this a suitable method for potato crops.
- Cultivars differ in resistance to slugs.
- Check cultivar resistance in the British Potato Variety Database.
- Do not grow a susceptible cultivar at a site with a risk of slug infestation.
- Ferrous sulphate pellets (e.g. “Sluxx HP”, Certis; or “Ironmax Pro”, DeSangosse) may be applied for control of slugs.
- Limited use of metaldehyde (e.g. “TDS Major”, DeSangosse) may still be made in accordance with the metaldehyde stewardship scheme but withdrawal dates are:
- 31 December 2020 for sale and distribution
- 31 December 2021 for use up, storage and disposal
- Pellets should be applied at a time when slugs can be expected to be active on the surface, e.g. just before or after rain or irrigation.
- Slugs which have been poisoned by ferrous sulphate may not be found on the soil surface, so population assessments should be repeated to check efficacy and persistence of control.
- See the manufacturers’ websites for details of product use.
See the manufacturers’ websites for details of agrochemical use.
Control of slugs without metaldehyde 2019 (Integrated control, including effects of carabid beetles)
Control of soil pests 2015 (Includes slug risk assessment)
Updates on potato pests 2014 (Includes cultural control)
Slugs 2013 (Invasive slugs; species pictures and descriptions for pest slugs; sub-lethal poisoning can result in pellet avoidance)
Slug control updates 2012 (Includes control of slugs with ferric phosphate)
Pest control 2010 (Includes control of slugs with ferric phosphate)
Nemaslug application 2010 (Potential for application in irrigation water)
Slug control 2009 (Control with and without metaldehyde)
Soil pest control updates 2008 (Includes influence of temperature on metaldehyde efficacy; slug feeding behaviour)
Pesticides update 2007 (Includes risk of molluscicides to non-target organisms)
Pest control updates 2006 (Includes introduction to ferric phosphate for slug control)
Slugs 2005 (Degradation of slug pellets; attractiveness of baits)
Slugs 2004 (Developments in biological control with nematodes)
Slugs research 2003 (Effects of various agrochemicals on survival of slug eggs; distances travelled by slugs)
Slugs 2002 (Identification of pest species; control in relation to activity and life cycle)
Slug control 2000 (“Nemaslug” for biological control with nematodes; period of efficacy of slug pellets in wet and dry conditions)
Slugs 1998 (Trapping slugs; introduction to biological control with nematodes)
Slugs 1997 (Slug biology and integrated control)
Slug identification this link opens in a new window.