Survival of cattle ticks in central Queensland pastures

Abstract

Observations on the gradual distension and shrinkage of cattle tick larvae (Boophilus microplus (Canestrini)) confirmed that they can take up water from, or lose water to, the atmosphere under suitable conditions. Further evidence was obtained that partially desiccated larvae can drink when in contact with free water. Consideration of the relative humidities recorded over sward adjoining a creek, during a drought, suggested that larvae would be able to absorb moisture during the 9-hr period before dawn. Dew m-as also available to the larvae in drought time, and on most mornings when observations were made. In the laboratory, larvae in cultures supplied with water droplets lived longer than those in similar cultures not supplied with water. Larval clusters on artificial supports out of doors lived longer if protected by fabric shades. At intervals over 2 years, female ticks were placed in grassland near Rockhampton and at Yeppoon, Qld., under simulated natural conditions. The times of hatching and periods of survival of the larvae were observed. In contrast with the marked decrease in tick fertility which occurs in the winter in south Queensland, ticks put out throughout the winter at Rockhampton laid large numbers of fertile eggs. Very few larval progeny of ticks put out in summer survived 3 months after the date of placement of the parent female. Progeny of ticks put out in the winter persisted up to 54 months after the date of placement of the parent. A graph of the 'pre-hatch' (pre-oviposition plus developmental) periods against screen temperatures followed the trend expected from laboratory data, but the difference between actual and computed hatching dates was large in some cases. Actual hatching date was usually later than computed hatching date, both for ticks in the soil and for ticks in humidified containers in a meteorological screen. The comparatively short survival periods of larvae in the central Queensland summer indicated the practicability of controlling the cattle tick by temporarily destocking pastures.