Mapping, characterisation, and comparison of the spatio‐temporal distributions of cabbage stem flea beetle (Psylliodes chrysocephala), carabids, and Collembola in a crop of winter oilseed rape (Brassica napus)

The spatio‐temporal distribution of Psylliodes chrysocephala (L.) (Coleoptera: Chrysomelidae), a pest of oilseed rape (Brassica napus) (L.) (Cruciferae) and its potential predators, carabid beetles, within a crop of winter oilseed rape is described. The distribution of Collembola, a potential alternative food source for the predators, is also investigated. Insects were collected from spatially referenced sampling points across the crop and the counts mapped, analysed, and the degree of spatial association between the distributions determined using Spatial Analysis by Distance IndicEs (SADIE). Immigration into the crop by adult P. chrysocephala occurred from two edges and resulted in a non‐uniform distribution of the pest within the crop. Infestation of rape plants by P. chrysocephala larvae was greatest within the central area of the crop. Significant spatial association between adult female P. chrysocephala and the larval infestation of plants occurred throughout October. Three carabid species were active and abundant during peak pest immigration into the crop, viz., Trechus quadristriatus (Schrank) (Coleoptera: Carabidae), Pterostichus madidus (Fabricius) (Coleoptera: Carabidae), and Nebria brevicollis (Fabricius) (Coleoptera: Carabidae). Two of these species, T. quadristriatus and P. madidus, showed significant spatial association with the larvae of P. chrysocephala during October. All three carabid species showed a significant spatial association with Collembola during mid‐September, indicating that the latter may be an important food source for carabids during this period. In laboratory feeding experiments, only T. quadristriatus consumed the eggs of P. chrysocephala suggesting that, in the adult stage, this species may be the most important of the naturally occurring carabids as a predator of P. chrysocephala in the field. Adult T. quadristriatus may be a valuable component of an Integrated Pest Management strategy for winter oilseed rape, and the conservation of this species could be beneficial.

[1]  Joe N. Perry,et al.  Red–blue plots for detecting clusters in count data , 1999 .

[2]  I. Williams,et al.  Pest-predator spatial relationships in winter rape: implications for integrated crop management , 2000 .

[3]  A. Burn.  The role of predator searching efficiency in carrot fly egg loss. , 1982 .

[4]  Joe N. Perry,et al.  MEASURES OF SPATIAL PATTERN FOR COUNTS , 1998 .

[5]  S. Finch.  Effect of beetle size on predation of cabbage root fly eggs by ground beetles , 1996 .

[6]  D. V. Alford.  Chemical control of the cabbage stem flea beetle, Psy Modes chrysocephala, on winter oil‐seed rape , 1977 .

[7]  Joe N. Perry,et al.  Spatial analysis by distance indices , 1995 .

[8]  J. Free,et al.  The infestation of crops of oil-seed rape (Brassica napus L.) by insect pests , 1979, The Journal of Agricultural Science.

[9]  Professor Dr. Hans-Ulrich Thiele.  Carabid Beetles in Their Environments , 1977, Zoophysiology and Ecology.

[10]  C. Nilsson.  Yield losses in winter rape caused by cabbage stem flea beetle larvae (Psylliodes chrysocephala (L.)) [Brassica napus var. oleifera] , 1990 .

[11]  D. V. Alford.  Observations on the cabbage stem flea beetle, Psylliodes chrysocephala, on winter oil-seed rape in Cambridgeshire , 1979 .

[12]  I. Williams,et al.  First steps to assess the importance of epigaeic active polyphagous predators on oilseed rape insect pests with soil pupating larvae. , 2000 .

[13]  L. Winder.  Predation of the cereal aphid Sitobion avenae by polyphagous predators on the ground , 1990 .

[14]  J. Thioulouse.  SPACE-TIME STRUCTURES IN A WINTER RAPE PEST POPULATION, PSYLLIODES CHRYSOCEPHALA (COL., CHRYSOMELIDAE): METHODOLOGICAL PROPOSALS AND BIOLOGICAL INTERPRETATIONS , 1987 .

[15]  M. J. Weiss,et al.  Influence of Tillage Management and Cropping System on Ground Beetle (Coleoptera: Carabidae) Fauna in the Northern Great Plains , 1990 .

[16]  B. Mitchell.  Ecology of two Carabid beetles, Bembidion lampros (Herbst) and Trechus quadristriatus (Schrank). I. Life cycles and feeding behaviour. , 1963 .

[17]  J. Perry.  Measures of spatial pattern and spatial association for insect counts , 1998 .

[18]  K. D. Sunderland,et al.  The diet of some predatory arthropods in cereal crops. , 1975 .

[19]  T. Hance,et al.  Agriculture and ground-beetles populations. The consequence of crop types and surrounding habitats on activity and species composition. , 1990 .

[20]  L. Bonnemaison.  Insect Pests of Crucifers and Their Control , 1965 .