The influence of Western corn rootworm seed coating and granular insecticides on the seasonal fluctuations of soil nematode communities in a maize field

Western corn rootworm, Diabrotica virgifera virgifera, is a pest that needs to be controlled with chemicals in the maize monoculture. The aim of this study was to examine the influence of insecticides on nematode communities in a maize field. Four soil treatments were used in this experiment: variant 1 — a granular application with tefluthrin (199.5 g a.i./ha); variant 2 — a granular application with clothianidin (110 g a.i./ha); variant 3 — a seed treatment with clothianidin (1.25 μg a.i/seed); and control — a maize field without insecticides.

During the investigated period, a total of 19 117 soil nematode individuals were captured and 9 orders, 33 genera and 37 species were identified. Acrobeloides nanus, Cephalobus persegnis, Eucephalobus striatus and Basiria gracilis were the dominant species, accounting for 48 % of the total number of individuals. The mean abundance and species diversity index were significantly lower for variant 2. Bacterial feeders were the dominant trophic group for all 4 variants. The numbers of nematodes in particular trophic groups (i.e., bacterial feeders, fungal feeders and omnivores) were significantly different between variant 2 and the control. The Σ Maturity index, Maturity index and Plant parasitic index did not show significant differences among the variants. The higher values of the Enrichment and Structure indices were observed in the first month of the investigation in all 4 variants. A cluster analysis showed that nematode species population densities were strongly affected by the date of soil sample collection and by the variants used in the experiment.