Archive Article: 1997/09/06
Barrier method
SCIENTISTS are attempting to exploit the slugs Achilles heel – its entire foot. The thin mucal coating, which is more than 95% water, is essential for the slug to move.
It also protects the skin and layers below which are quite permeable, allowing toxins or irritants to enter the bloodstream quite easily.
Using nerves on its tentacles and around its mouth, the slug senses anything that might affect the physical properties of its mucus and goes to great lengths to avoid it.
Finding something which produces this reaction but is otherwise non-toxic in the field is the objective of IACR-Rothamsted work. Surfactants, already known to alter mucus in vitro, are one area of particular interest.
The research team has taken the most promising chemicals into the field. The idea is to use them as a physiochemical barrier to slugs. Brussels sprouts provide an ideal test ground for this method.
Sprout growers are plagued by slugs which climb the stalks and rasp small holes in the outer leaves of the developing buttons – the damage is only superficial but just a few disfigured sprouts can mean the rejection of the whole load.
But while an electrostatically charged surfactant aimed 15cm (6in) up the sprout stalks gives good coverage in dense crops, the surfactants proved ineffective in wet conditions.
If only more persistent formulations could be found the concept of barring access from below might be made to work.