HOST-SEEKING OF BLACKLEGGED TICK (ACARI, IXODIDAE) NYMPHS AND ADULTS AT THE WOODS PASTURE INTERFACE

To clarify the risk of pastured livestock for exposure to Ixodes scapu laris Say (Acari: Ixodidae), we estimated the host-seeking activity of nymph and adult blacklegged ticks at the woods-pasture interface on h orse farms in Maryland. Parallel linear transects of 100 m length and 1 in width were sampled repeatedly in pastures and adjacent woodland l ocations during periods of nymph (early summer) and adult (fall and sp ring) host-seeking activity. Data collected over two successive years indicated that adults were most abundant in ecotonal vegetation at the wood's edge, median values of 6.4 and 2.2 ticks per 100 m2 sample dur ing fall and 1.2 and 0.5 ticks per 100 m2 sample for spring periods. N ymphs were most abundant in the shallow woods location, median values of 4.2 and 35 ticks per 100 m2 sample, followed by the deep woods and wood's edge locations. Host-seeking nymph and adult black-legged ticks also were collected repeatedly in pasture vegetation, median values r anging from 0.2-0.8 ticks per 100 M2 sample, with a progressive decrea se in abundance from the fenceline into pasture. Adults and nymphs bot h were uncommon more than 5 m into pastures, where only two adults and one nymph were captured in 84 (fall and spring) and 24 (summer) 100-m 2 samples, respectively. Levels of adult and nymph host-seeking in pas ture vegetation were spatially correlated with tick abundance in adjac ent woodlands when ticks were numerous; this condition presumably refl ects a spillover of ticks from the woodlands-based population. These f indings expand knowledge of blacklegged tick host-seeking behavior and establish a basis for the exposure of pastured livestock to nymphs an d adults.