In recent years, the slugs, mainly the Arionidae family, have been labeled as an economically important agricultural pest. For their control, growers most often use synthetically produced pesticides (i.e., molluscicides), especially because of efficiency and simple application. However, molluscicides can have a negative impact on the environment. Therefore, an increasing tendency to find alternative means and measures of slug control exists. One of the substances with potential molluscicidal action is wood ash. In our experiment, the effects of different types of wood ashes have been studied for their contact efficacy against slugs. Three types of wood ashes; sweet chestnut (Castanea sativa Mill.), black alder (Alnus glutinosa L.), and common hornbeam (Carpinus betulus L.) and their combinations in a ratio of 1:1 have been studied against the Arion slugs (Gastropoda, Arionidae). Contact molluscicidal activity was studied by rolling the slug in the wood ash and by creating an ash obstacle. We studied different parameters, such as mortality rate, eating capacity (nourishment), weight changes, and the (non)crossing of the wood ash obstacle. No molluscicidal effect was confirmed in any of the wood ashes examined by the rolling contact activity test. In contrast, we have demonstrated the molluscicidal effect of wood ash as a crossing obstacle. Among the ashes used, the wood ash of a common hornbeam had the best contact efficiency. Therefore, the use of wood ash in the protection of plants against slugs may represent a potential breakthrough. Nevertheless, additional research in outdoor conditions is needed.