Use of ivermectin-treated baits for management of the lone star tick, Amblyomma americanum L. (Acari:Ixodidae)

Ivermectin-treated corn was fed to deer from March to August 1994 and 1995 in a tick-infested area of Fairfield Glade, Cumberland County, Tennessee. All life stages of Amblyomma americanum L. were collected from an ivermectin-treated and a non-treated area in 1994 and 1995.

In 1994, 3.4 times as many adult ticks were collected in the treated area as compared to the non-treated area. Approximately 2 times as many nymphs and 1.6 times as many larval masses were collected in the non-treated area. Adults were 1.7 times and nymphs were 1.5 times more numerous in the treated area as compared to the non-treated area in 1995.

Statistical analysis revealed that ivermectin treatment had no effect on the densities of lone star ticks in the treated area in 1994 and 1995. However, there was a reduction in the numbers of all life stages collected in the treated area in 1995 compared to 1994. Also, the number of larval masses collected in the treated area in 1994 was 4 times less than what would have been expected when compared to the high numbers of females collected earlier in the season and the number of masses collected in the non-treated area. Though no significant reductions were found, ivermectin may be causing a slow reduction in free-living tick populations in the treated area. An extended study and treatment schedule could further reveal the effects of ivermectin treatment.

Seasonal distributions in 1994 and 1995 are presented for the life stages of A. americanum, based on numbers of individuals collected in the non-treated area. Differences in apparent seasonal densities due to sampling method were found for nymphal and adult ticks. Significantly more nymphs were collected from the wooded areas than the grassy areas. No significant differences were found in the numbers of females and larval masses collected in the wooded and grassy areas.