Preliminary studies using polymers to extend the protective period of acaricides in the control of the cattle tick Boophilus microplus.

Abstract

Animal Production in Australia PRELIMINARY STUDIES USING POLYMERS TO EXTEND THE PROTECTIVE PERIOD OF ACARICIDES IN THE CONTROL OF THE CATTLE TICK Boophilus microplus J.A. CONNELL*, P.R. GREEN* and P.S. HOPKINS* SUMMARY The concept of using polymer emulsions combined with the normal water/ acaricide mixture, and the misting of this solution for control of the cattle tick Boophilus microplus was investigated in three experiments. Under field conditions acaricide alone gave 11-12 days protection compared with about 25 days for acaricide/polymer emulsions. The latter exceeds the 21-day life cycle of the cattle tick. INTRODUCTION The importance estimated million at cattle tick Boophib~ microp~us continues to be of major economic to cattle production. Its total cost to industry and government were in excess of $40 million in 1973 (Anon,1973), this would exceed $100 current prices. Savings in costs associated with control of the tick using acaricides would be achieved if the period of protection obtained after acaricide treatment was extended. This paper describes three experiments which examine this possibility by the use of polymer emulsions designed to extend the active life of acaricides applied to cattle. MATERIALS AND METHODS Dipofene 60 was the acaricide used in all experiments. with polymer/water emulsions. All dilutions were w/v. + This was combined The polymer/acaricide emulsions were misted onto cattle using a final concentration of acaricide which was twice the recommended dipping strength. was done to counteract the lower volumes applied by the mister. This Polyme r durabili ty was subjective ly assessed at frequen t in.tervals by examining th e extent t o which the compo und retained adherence to the animals coat. Experiment 1 was designed to evaluate the potential use of polymers under pen conditions. Experiments 2 and 3 describe field investigations undertaken in south east Queensland. Tick burdens were monitored according to the method of Wharton and Utech (1970). Hereford steers were used in all experiments. Experiment 1 Polymer Emulsion: RE454 at 20% solids. Five groups each of three steers were treated as shown in Table 1. The animals were artificially infested with a total of 4.5g of larvae ticks over seven ;k Animal Research Institute, Department of Primary Industries, Yeerongpilly, Qld, 4105. + Chloromethiuron. Animal Production in Australia occasions between days 2 and 19 after first infestation for the and were undergoing normal hair post treatment. The exper&ment post treatment and placed in covered moats 20 days collection of ticks. All animals had summer coats shedding. The experiment was terminated on day 40 extended over the months February to April. Experiment 2 Polymer Emulsion: RE460 at 20% solids. Twenty-four steers previously exposed to ticks were randomly stratified into three equal groups on the bases of their tick burdens on two occasions prior to commencement. The groups and treatments are shown in Table 2. Ticks were counted three experiment was terminated when control group. The experiment during which the total rainfall times per the tick extended recorded week. All animals had summer coats. The burden of each group equalled that of the over the months of February and March was 69mm. Experiment 3 Polymer Emulsion: RE460 and RE484 at 20% solids. Twenty-five steers previously exposed to ticks were randomly stratified into five equal groups on the basis of their tick burdens on four occasions prior to commencement. The groups and treatments are shown in Table 3. Ticks were counted twice a week. experiment was terminated when the tick control group. The experiment extended during which the total rainfall recorded All animals had summer coats. The burden in each group equalled that of the over the months of November and December was 169mm. RESULTS Experiment 1 TABLE 1 The effect of RE454/Dipofene treatment on tick control + recommended concentration, +t Marino Air Mister The numbers of engorged ticks dropped from each group indicate that Dipofene mixture (0.36%) successfully extended the protective period from normal 6-7 days expectancy to 10 days. The number of ticks recovered in was approximately half of any other treatment. Durability of the Polymer days. 342 polymer/ the Group 4 was 16 Animal Production in Australia Experiment 2 The results of the first field experiment are given in Table 2. TABLE 2 The effect of RE460/Dipofene treatment on tick control The durability of the polymer was 20 days. Experiment 3 The results of the second field experiment are given in Table 3. TABLE 3 Group Treatment The effect of RE460/Dipofene and RE484/Dipofene on tick control. 1 Control 2 6.8 l/hd Dipofene (0.18%) hand sprayed 12 1,284 3 5.1 l/hd Dipofene (0.36%) misted 8 1,788 4 5.5 l/hd RE460/Dipofene (0.36%) misted 23 88 5 4.2 l/hd RE484/Dipofene (0.36%) misted 14 650 Days protection Tick No. 0 11,440 The durability of polymers RE 460 and RE484 was 18 and 10 days respectively. The period of protection afforded by the incorporation of polymer was approximately 25 days under field conditions. DISCUSSION The extension of the period of protection up to 25 days (which exceeds the 21-day life cycle of the cattle tick) shows promise in the light of the normal expected protection of up to 10 days with an acaricide without the use of polymer. If a polymer could be developed with a durability in excess of two life cycles of the tick, then even greater promise for tick control would be available to the industry. The three polymers investigated were compared in an endeavour to select one having the greatest durability. RE460 proved to be the most suitable polymer evaluated. Collateral studies revealed that the application of polymer alone afforded no measure of additional protection. 343 Animal Production in Australia It appears the period of control achieved with the polymer/acaricide is closely related to the durability on the coat. Despite the greater rainfall encountered in experiment 3 compared with experiment 2, this did not appear to effect the period of protection by the polymer. No doubt there are a number of physical factors all of which could effect the durability including hair shedding, proximity of the polymer to the skin of the animal, abrasion by other animals and licking. Boophi hs mi mop hs . Testing throughout these experiments was for the control of the cattle tick The results obtained suggest that the extension of research to other ectoparasites using the described techniques could be warranted. ACKNOWLEDGEMENTS The authors wish to thank the Australian Meat Research Committee for their generous support, and Monsanto Australia Pty. Ltd. for their continued support in the development and supply of differently formulated polymer emulsions. REFERENCES . ANON.(1973). 'Cattle Tick in Australia' (Australian Government Publishing Service: Canberra) WHARTON, R.H. and UTECH, K.B.W. (1970). J. Aust. Ent. Soc. = : 171. 9