Bücher Ackerunkräuter
Fritz-Köhler, W. (1996): Chrysomelid and curculionid beetles associated with arable weeds, their ecology and biogeography in Central Europe, and a study on crop margins not treated with agrochemicals. - Agrarökologie (Bern) 19, 1-138.


Following an account of the history of agriculture and the arable weed vegetation as well as of the causes for recent changes in the arable weed vegetation, the beetle fauna of the wildflowers of arable fields is dealt with. In a table the relationships between Central European chrysomelids, curculionids and wildflowers of arable fields are presented. Altogether 347 beetle species are associated with 237 species of arable weeds. Like their host plants, the majority of monophagous beetle species (88%) are immigrants from the Mediterranean and southeastern regions, whereas most of the oligophagous and polyphagous chrysomelids and curculionids (56%) are autochthonous in Central Europe. 

Since in Central Europe there is a tendency for the number of species to decrease towards the north, it is concluded that the majority of the chrysomelids and curculionids originating from neighbouring zoogeographical regions must be considered thermophilous faunal elements. As many as 80% of these phytophagous species have been reported from the Rhineland. Like the wildflowers of arable fields, the beetles associated with these plants are highly threatened, partially even possibly extinct, due to increasingly intensive agriculture and, particularly, the loss of their host plants. It is worth noting that the beetles, especially the monophagous species, are threatened much more than the wildflowers of arable fields. 84 out of 222 species of arable weeds are threatened or possibly extinct, whereas 123 in 249 species of oligophagous or polyphagous beetles and 26 in 31 species of monophagous beetles are threatened or possibly extinct. An extensive distribution of the host plants is an essential requirement for the expansion or re-establishment of populations of phytophagous, especially monophagous beetle species. Three examples are presented to illustrate power and speed of dispersal. 

In the surroundings of Euskirchen the effects of the North Rhine-Westphalian field margin programme on the chrysomelid and curculionid beetles were studied. From April to October 1988 the study sites were manually sampled. A total of 3,222 specimens belonging to 153 species of Chrysomelidae and Curculionidae were collected; 42 of these species were recorded only on crop margins, 46 species exclusively on field margins and 65 species in both biotopes. The chrysomelid and curculionid fauna of the sites is represented by a comparatively large number of species, but largely consists of euryecious, widely distributed and polyphagous elements. 

The number of species and specimens recorded is strongly correlated with (a) the period of time during which a site participated in the field margin programme, (b) the density of potential host plants, (c) the degree of host plant cover, (d) the number of plots in a study site in which potential host plants was present, and (e) the diversity of biotops surrounding the fields. 

A synchronization between the specific life-cycles of the beetles and the mode of cultivation on the respective site was observed. The absence of several species is believed to be caused by interferences with their life-cycles. The application of herbicides in arable fields affects the phytophagous beetle fauna of wildflowers much more strongly than their host plants. The faunistically remarkable records of beetles for the Rhineland, particularly those of Phyllotreta consobrina, Ochrosis ventralis and Ceratapion armatum, are commented on. 

In conclusion, recommendations regarding the continuation and improvement of the field margin programme are presented from an entomological point of view. 

Keywords: arable fields, wildflowers, Chrysomelidae, Curculionidae, immigration, host plant association, threatened species, field margin programme, effects, recommendations