On the use of fungicides in ecological seed burial studies

Evidence for effects of saprophytic fungi on buried seed demography is usually obtained from studies involving the simultaneous burial of fungicide-treated seeds and of untreated seeds. However, any potential influence of fungicide treatment on seed dormancy levels is generally ignored in these studies. Also, some studies assume that a combination of several fungicidal compounds provides better protection against a broader range of fungi, ignoring chemical interactions that may potentially occur between different compounds. To investigate these issues, we carried out a six-month burial experiment using seeds of Anthriscus sylvestris (L.) Hoffm., Centaurea nigra L., and Daucus carota L., and three substrates differing in organic matter content. Three fungicidal compounds, captan, iprodione, and mancozeb, were applied alone and in combination, including an untreated control. All fungicidal compounds and combinations thereof provided protection against fungal-induced seed mortality, and except for a low efficacy of iprodione in protecting seeds of Anthriscus, there were no pronounced differences in seed mortality between different fungicide treatments. Captan temporarily inhibited germination in Centaurea, whereas a similar inhibition in Daucus seeds caused by mancozeb was more long-lasting, suggesting an induction of secondary dormancy. Organic matter content only had a negligible influence on these results. Our results suggest that the basic conclusions from most seed burial studies are robust with respect to their choice of fungicide. We conclude by discussing further implications of our findings for the design and interpretation of seed burial studies.