Fungicide effects on wild plants: insights from a global meta-analysis

Many studies have investigated plant-pathogen interactions by testing whether fungicides affect plant survival, growth, biomass, and/or diversity. Here, we synthesize these studies using a global meta-analysis of 369 experiments from 62 papers that compared plants treated with fungicide to untreated controls. Overall, fungicide increased the survival of native plant species and community biomass but decreased diversity, mirroring the effects of fencing out vertebrate herbivores. There was no overall effect on plant growth. However, analyses of subsets of the data revealed a more varied and complex picture, with few consistent results. Strong geographical biases in sampling and small sample sizes for many combinations of variables make it difficult to distinguish between alternative explanations for this variation in fungicide effects. The results, overall, are largely consistent with a role for fungal pathogens in the maintenance of community diversity, but not with the latitudinal biotic interaction hypothesis. Future studies should aim to fill the gaps in the geographical spread of studies, standardize the methods as far as possible, and use molecular techniques to characterize the impacts of fungicide treatments on both target and nontarget organisms.