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Yellow water traps are a decisive factor in the forecasting system for Psylliodes chrysocephala, the Cabbage stem flea beetle. In most parts of Germany a threshold of 50 imagines per yellow water trap within three weeks is established. In Germany two types of yellow water traps are widely used: an angular (26 × 33 cm) and a round type (22.4 cm diameter). The use of a grid at the top of the yellow water traps is recommended to prevent bees from drowning. The aim of this study carried out on 28 fields all over Germany was to investigate the effects of different types of yellow water traps on Cabbage stem flea beetle catches. Traps were used with and without grid and placed on the soil surface or dug into the soil. Beetle numbers differed significantly between some of the types of yellow water traps, but the difference in densities was in an acceptable range given the overall high variability induced by farmers. [ABSTRACT FROM AUTHOR]