For hoverflies about 6,000 species in 200 genera have been described, many of them threatened and documented in red lists. One of the main causes of endangerment are intensive agricultural management practices. The adults hoverflies feed mainly on nectar and pollen and are important pollinators, while the larvae eat a wide range of foods. In some species, the larvae are insectivores and prey on aphids, thrips, and other plant-sucking insects. Aphids alone cause tens of millions of dollars of damage to crops worldwide every year, thus aphid-feeding hover-flies are being recognized as important natural enemies of pests in agriculture.

To assess different crop production practices regarding their impacts on hoverflies the following assessment parameters were taken into account:

1. the suitability of the crop type to provide beneficial habitat conditions for this insect species.
2. the time- and operation-related risk potential of single operations to diminish the habitat potential during periods with the highest abundance of hoverflies on agricultural plots,
3. the risk associated to the application of nitrogen fertilisers influencing height and density of the vegetation and therewith establishment of accompanying wild flora species within the crop stand as food plants or host plants of their prey and
4. the number of insecticide and herbicide treatments due to direct lethal effects in case of insecticides and indirect effects on the availability of food resources in case of herbicides.

All alternative production practices of all crops defined for the model were assessed by their goal achievement levels using a fuzzy logic tool with the optimum being a zero risk for hoverflies to get negatively affected by agricultural activities.

Best ratings were given to permanent and rotational set aside. Alfalfa and grass clover mixtures for forage use scored well, too. Grassland and cereals good medium marks. The least favourable results were given to sugar beets and potatoes due to the high pesticide intensities for these crops.