Impact of potato cultivation in the vicinity of the alfalfa field on diversity and abundance of terrestrial predators, and density of Leptinotarsa decemlineata in Ardabil region

The Colorado potato beetle, Leptinotarsa decemlineata (Say) (Col.: Chrysomelidae) is the most important phytophagous pest of potato in Iran. In this research, diversity and abundance of terrestrial predators, and density of Colorado potato beetle eggs, larvae and adults were studied in potato rows located at 5, 10, 15, and 20 m from the alfalfa field (in the potato field adjacent to the alfalfa field) along with the control (the sole potato field) in Ardabil region during 2014 and 2015. In this study, eight terrestrial predator species in the control potato field and fourteen terrestrial predator species in the potato field adjacent to the alfalfa field were collected using pitfall trap and identified, amongst which spiders and carabid beetles had more relative abundance. The Shannon diversity index (H’) for terrestrial predators in the potato rows located at 5, 10, 15, and 20 m from the alfalfa field (in the potato field adjacent to the alfalfa field) was significantly higher than in the control potato field. During two years, the abundance of spiders and Carabid beetles decreased with increasing distance of the potato rows from the alfalfa field. Moreover, the density of Colorado potato beetle eggs, larvae and adults increased with increasing distance of the potato rows from the alfalfa field. Therefore, use of the strip cropping of potato and alfalfa (with 10 m of the potato strips width) could be recommended to the farmers in the integrated management of Colorado potato beetle.