Effect of herbicides on butterfly populations of an electric transmission right-of-way

Abstract

A study was made in 1995 and 1996 of the butterfly populations on a 500 kV transmission line of PECO Energy in the Piedmont Region of eastern Pennsylvania. The objective was to compare the long-term effect of 3 herbicide sprays with 2 mechanical methods of right-of-way (ROW) maintenance on the number of butterfly species and their abundance. The wire zone/border zone technique was used on all units to maintain shrubs on border zones. Butterfly counts were made at 5 times over the growing season to coincide with flowering of common plant species. There was no discernible adverse effect of herbicide spray maintenance in comparison with mechanical methods on either the number of species, or individuals, of the ROW butterfly population. Twenty butterfly species were present on the handcutting unit and 19 to 21 on the 3 herbicide units. The number of individual butterflies present on the 3 herbicide units ranged between 122 to 154 in contrast to 116 on the handcut control unit.