Interactions of gulf cordgrass, Spartina spartinae (Trin.) Merr. ex Hitchc., habitat with ixodids on the South Texas coastal plain

Abstract

Many ixodid species on the South Texas coastal plain can transmit pathogens to their hosts. Substantial areas are dominated by gulf cordgrass, Spartina spartinae (Trin.) Merr. ex Hitch. The S. spartinae habitat was examined in terms of abiotic and biotic factors that likely impinge upon ixodids using the plant for questing. Natural enemies, temperature, humidity, and plant structure were investigated as possible mortality factors and improving ixodid survival. Spartina spartinae (soil and foliage) harbored few natural enemies of ixodids, and soil salinity was nonlethal. Conditions were cooler and more humid inside S. spartinae clumps than in the canopies; hence, questing ixodids can rehydrate inside the clump when threatened by desiccation. Leaves were mostly “V” shaped in cooler months and, during warm months, the tightly folded leaf slot predominated, into which larvae crawled. Immature ixodids were more abundant in the concave side of the “V”-shaped leaves than on the exposed convex side. Larvae sought refuge from potential lethal ambient air conditions by entering tight warm season leaf folds. The leaf “V” and fold offer opportunities for rehydration on the leaf without moving to the clump’s base. In addition to five other species collected on the grass, a relatively heavy larval southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini), population was detected, suggesting that abundances in the South Texas cattle fever tick eradication quarantine zone are increasing and might spread further into Texas.