Seasonal and Annual Abundance of Amblyomma americanum (Acari: Ixodidae) in Central Georgia

Abstract

Seasonal and annual changes in the abundance of Amblyomma americanum (L.) larvae, nymphs, and adults were monitored over a 5-yr period in the Piedmont physiographic region of Georgia. Tick abundance was monitored with cloth drags (all life stages) and CO2-baited cloth panels (nymphs and adults) monthly during March through September from 1987 through 1991. Larvae appeared in substantial numbers in July and were most numerous in August and September. Small numbers of unfed larvae apparently overwintered each year based on their presence during March, April, or May. Nymphs were most numerous from April through June and declined to much lower numbers by August and September. Adults were most numerous from March through May and virtually disappeared by August. These seasonal patterns were similar to those reported for A. americanum at other southeastern locations. Each life stage exhibited similar trends of annual abundance with an increase in 1988 followed by a relatively steady decline to levels equivalent to or below initial 1987 values by 1991. Major environmental variables that potentially could have influenced annual abundance were identified from Haile & Mount's (1987) computerized model of A. americanum population dynamics. Habitat type, host density, and day length were constants and rationally could be excluded as causes of annual variations in abundance; weather and host-finding rate were presumed to have been primarily responsible for these annual differences.