A vegetable brassica based diet to test individual traits to control the cabbage root fly

The cabbage root fly Delia radicum (Diptera: Anthomyiidae) is a major insect pest in vegetable brassica crops in Switzerland. Due to its lifestyle and limitations in the use of insecticides, controlling of the cabbage root fly is challenging. It is the aim of several projects to find new measures to control the cabbage root fly. Therefore, laboratory, greenhouse, semi-field and field trials are conducted. Each of these trials has to struggle with a complex system composed of host plants, plant nutrition, soil and soil conditions, insects, control agents, i. e. macro- or microorganisms, chemicals, accompanying plants etc. To elucidate the efficacy of a single trait in preliminary trials, an experimental set-up with a test system is needed to study the effect of individual parameters under standardized conditions. Artificial rearing and test systems are known for different insect species including insects belonging to the Diptera. Based on these experiences, a vegetable brassica based diet was developed for experimental purposes. Using cabbage root fly larvae from the traditionally rearing system, the vegetable brassica based diet was optimized. First trials with mated naïve cabbage root fly females were conducted to study the practicability of this vegetable brassica based test system. Additional trials were conducted to study the repellency of Salvia officinalis water extract against the cabbage root fly. Mated cabbage root fly females accepted the vegetable brassica based diet for oviposition and larvae developed successfully. The efficacy of the repellent Salvia officinalis water extract was tested using this newly developed test system. The already reported repellent efficacy (Hirschfeld and Klingauf, 1988; Nottingham, 1987) was verified with this system. The vegetable brassica based diet is a useful test system to study the effect of single parameters to control the cabbage root fly.