Red imported fire ant (Hymenoptera : Formicidae) populations in Texas highway rights-of-way and adjacent pastures

Do disturbed habitats along highway rights-of-way encourage the establishme nt and spread of the red imported fire ant, Solenopsis invicta Buren, in Te xas? The objective of this study was to determine if highway rights-of-way harbored S. invicta populations that were significantly different from thos e in adjacent pastures. Data on S, invicta populations were collected from three transects along highways within S. invicta-infested areas of Texas. O ne north-south transect, a southern east-west transect, and a northern east -west transect were established in Texas and extended 1,678 km. Twenty-eigh t sites, approximate to 80 km apart along transects, were visited between 1 4 May and 1 lune 1996. Numbers of S, invicta mounds, mound vitality ratings , ants collected in bait cups, and vegetative characteristics were measured in rights-of-way and in adjacent pastures at each site. No significant dif ferences in pooled (n = 28) mean numbers or vitality of S. invicta mounds w ere detected in rights-of-way as compared with those of adjacent properties . However, significantly more S. invicta colonies than expected were found on roadbeds (less than or equal to1.0 m from paved surfaces) as compared wi th the remainders of rights-of-way and to adjacent pastures. Roadbed coloni es ware also smaller, which suggested that colonies were more recently foun ded than in the remainders of rights-of-way. hound population densities and numbers of ants in bait cups were not well correlated with vegetative char acteristics measured in this study. In Texas where S. invicta is well estab lished, S. invicta is in a population equilibrium between highway rights-of -way and adjacent pastures. However, highway roadbeds may offer an early su ccessional habitat fur S, invicta colonies and may require special survey a nd pest management attention, especially along the frontiers of infestation in Texas.