Flower strips in sugar beet cultivation enhance biodiversity and beneficial insects

Since 2018, annual and perennial flower strips were integrated into sugar beet fields on the Südzucker AG’s experimental farm Kirschgartshausen (Baden-Württemberg/ Germany). To measure the effects of the flower strips on biodiversity as well as on beneficial insects and pests in comparison to the sugar beet field, standardized sweep-net samples were analyzed from May to September. The captured individuals were divided into four functional groups: pollinators, natural enemies, pests and other invertebrates. In the flower strips, 4.6 times more invertebrate biomass and 2.4 times more individuals were captured than in sugar beet fields. Pollinators were recorded almost exclusively in the flower strips. Natural enemies were 4.7 times more abundant in flower strips than in sugar beet fields and were also much more diverse there. In addition, the number of braconid wasps, chalcid wasps, ladybugs, and damsel bugs increased between 2018 and 2020. Potential pests were 1.4 times more abundant in the flower strips than in the sugar beet field, but in the flower strips mainly bugs and pollen beetles occurred, which are not relevant pests in sugar beet cultivation. Whereas cicadas, the main pest in sugar beet fields, were 3.7 times less abundant in the flower strips than in the sugar beet fields. Overall, flower strips increase biodiversity. Perennial, species-rich mixtures are particularly valuable. Subdivided flower strips with staggered maintenance that offer habitat and refuge for insects in every season have proven successful.