Non-target effects of herbicides on soil nematode assemblages.

Background: Herbicides are used extensively to control weeds. However, little is known about the non-target effects of herbicides on soil nematode assemblages. The objective of this study was to determine whether herbicides affect the abundance of nematodes in specific trophic groups. Meta-analysis was performed, and the calculated effect size, lr, quantified the impact of herbicides on the abundance of total nematodes and five trophic groups (bacterivores, fungivores, plant parasites, omnivores and predators).

Results: Measurements of lr indicated that herbicides decreased abundance of both fungivores and predators; however, abundance of bacterivores, plant parasites and omnivores increased. Overall, total nematode abundance tended to increase in response to herbicide application.

Conclusion: The decrease in predator abundance suggests that herbicide application disturbs soil food webs. The increase in bacterivore and decrease in fungivore abundance suggest that bacterivores are more tolerant and both fungivores and predators more sensitive to herbicide applications. Herbicides also have non-target effects on omnivores, which may be due to the increased amount of food resources for omnivores after weed control. Additionally, the use of herbicides may result in a risk of an increase in plant-parasitic nematode abundance.