Seasonal dynamics of three harmful insect species on cabbage | Sezonska dinamika treh vrst skodljivih zuzelk na zelju

From the beginning of April to the beginning of November 2006, a seasonal dynamics of three harmful insect species - Swede midge (Contarinia nasturtii [Kieffer], Diptera, Cecidomyiidae), flea beetles (Phyllotreta spp., Coleoptera, Chrysomelidae), and diamondback moth (Plutella xylostella [L.], Lepidoptera, Plutellidae) - was investigated at the Laboratory Field of the Biotechnical Faculty in Ljubljana. The males were monitored with pheromone traps; the males of Swede midge were trapped with the traps of Swiss producer (Agroscope FAW, Wädenswill), while the adult flea beetles (trap type KLP+) and diamondback moths (trap type RAG) were trapped with the Hungarian traps (Plant Protection Institute, Hungarian Academy of Sciences). The pheromone capsules were changed in 4-week intervals, while the males were counted on about every 7 th day. The first massive occurrence of diamondback moth (1.6 males/trap/day) was established in the 2nd decade of April, and the pest remained active until the 2nd decade of September. The adults were the most numerous in the period between the end of May to the middle of June, but even then their number did not exceed three males caught per day. In the 1st decade of May, the first adult flea beetles were recorded in the pheromone traps, while their notable number (0.8 males/trap/day) was stated in the 3rd decade of May. Absolutely the highest number of the beetles was recorded in the 2nd (19 adults/trap/day) and in the 3rd (25 adults/trap/day) decade of July, and the pest occurred until the beginning of October. The first massive occurrence of Swede midge (0.4 males/trap/day) was established in the 2nd decade of May, while the highest number of males (8/trap/day) were caught in the 2nd decade of July. In the 3rd decade of October, the last adults were found in the traps. Based on the results of monitoring of three cabbage insect pests we ascertained that in the central Slovenia the Swede midge has 3-4 generations, the flea beetles has 1-2 generations, and the diamondback moth has 4 generations.