Silicon reduces slug feeding on wheat seedlings

Slugs are a serious pest of cereal crops, and recent emphasis in slug pest management has shifted from solely chemical towards integrated approaches. The objective of the present research was to test if boosted silicon (Si) and calcium (Ca) levels in wheat seedlings can reduce slug grazing. Laboratory experiments were conducted in which wheat seedlings were grown firstly, with soluble Si and Ca (with and without additional mineral N) or secondly, with six levels of soluble Si, and consumption of leave sections by the field slug (Deroceras reticulatum) was measured. Boosted foliar Si concentrations reduced consumption significantly (P < 0.001) compared to an untreated control and Ca treatments in a no-choice setting; a similar trend (P < 0.10), but with a higher variability, was observed in a simultaneous choice setting. It is shown for the first time that increasing the nominal Si concentration of treatment solutions in a geometric series (from 0 to 6 g sodium metasilicate nonahydrate l(-1)) translated into a logarithmic increase in foliar Si concentrations (from 5.0 to 19.4 g Si kg(-1) dry weight). When these leaves were offered simultaneously (choice setting), wheat leaves containing less than 10 g Si kg(-1) were consumed preferentially by D. reticulatum (P < 0.001), suggesting that Si concentrations as low as 1 % leaf dry weight may be effective at reducing grazing by slugs. It is concluded that boosting Si levels in cereals has potential as a novel tool in crop protection against pest slugs and snails. Various open research questions to advance this tool are identified.