Mortality of Unfed Nymphal Ixodes dammini (Acari: Ixodidae) in Field Exclosures

Nymphs of the deer tick, Ixodes dammini Spielman, Clifford, Piesman & Corwin, were studied in Westchester County, NY, to determine the seasonal mortality pattern and the potential for unfed nymphs to survive through the active season (May–August). Field-collected nymphal ticks were monitored in field exclosures, which prevented contact with mammals while not restricting habitat choice by ticks. In addition, nymphs were confined in small mesh packages and monitored in the field. In 1989, few (1.3%) ticks placed in exclosures in May–June survived until the end of August. The average mortality rate (proportion of ticks dying per day) in the exclosures was 0.04 ± 0.03 in 1989, 0.048 ± 0.03 in 1990. Ticks placed in mesh packages had 90% mortality after 46 d, 99% after 100 d, and 100% after 300 d. These results indicate that survival through the active season is rare in nymphal I. dammini in Westchester.