collection on the main island was a male collected on 

 November 29, 1985. 



Program policy was changed in regard to the smaller islands 

 of Culebra and Vieques. Animals on Vieques are not treated 

 on a scheduled basis, although this service is available at 

 nominal cost. Owners may apply for movement passes to 

 transport animals off the island, and once animals are 

 inspected and found clean, they are treated and allowed to 

 move to their destination. Those destined for slaughter are 

 treated. and escorted to the abattoir. Although managed herds 

 were put through routine treatment cycles, the feral cattle on 

 the island prevented a successful eradication effort. Plans to 

 deal with the issue are being formulated. 



Animals on Culebra receive routine treatment for tick control. 

 One herd is known to be currently positive for A. variegatum. 

 Eradication efforts have produced limited success. Animals on 

 the island may be moved to slaughter only after treatment and 

 under escort. 



1986 Boophilus Research Highlights 



Cattle Fever Tick Research Laboratory, USDA, Agricultural 



Research Service 



Because of the occurrence of acaricide resistance within 

 populations of Boophilus microplus in Mexico, there is a 

 possibility that acaricide resistant ticks could be introduced 

 into the United States. Such an introdwction should not create 

 an unmanageable problem, but additional research is needed 

 to characterize the nature of the resistance and to test the 

 efficacy of presently available and new acaricides. Therefore, 

 research on acaricide resistant B. microplus continues to be a 

 high priority at the Cattle Fever Tick Research Laboratory in 

 Mission, Texas. 



Each of 13 generations of a strain of S. microplus irom Tuxtia, 

 Chiapas, Mexico, have been exposed to increasingly higher 

 concentrations of coumaohos to select a highly resistant strain 

 of ticks. Ten groups of F., 3 larvae out of 42 had survival rates 

 of 70 percent or greater after exposure to 1 .0 percent 

 coumaphos. Groups of F.|2 Tuxtia strain larvae, ca. 45 times 

 less susceptible to coumaphos than non-resistant ticks, were 

 placed on Hereford heifers at intervals prior to dipping so that 

 when the cattle were dipped in 0.165 percent coumaphos, 

 they would be infested with all three parasitic life stages of the 

 resistant ticks. Simultaneously, an equal number of heifers 

 were infested with larvae of a susceptible strain. The percent 

 control of the susceptible strain was 99.6, but the percent 

 control of the resistant strain was 82.0. 



Evaluations of several new acaricides are planned, and tests 

 of flumethrin, a pyrethroid, have been completed. Two different 

 flumethrin formulations, a pour-on and an emulsifiable 

 concentrate, were evaluated. One ml. of 1 percent flumethrin 

 pour-on per 10 kg of body weight was applied evenly along 



the midline of the back from in front of the shoulders to the 

 tailhead to a group of cattle infested with all the parasitic life 

 stages of 6. annulatus. A second group of cattle, similarly 

 infested with S. annulatus, were treated by spraying them with 

 the emulsifiable concentrate at a concentration of 0.003 

 percent. Both formulations proved to be very efficacious. The 

 percent control obtained with the pour-on was 97 and with the 

 spray was 99.9. An evaluation of cyhalathrin, another 

 pyrethroid, is scheduled for this summer. A dipping test of a 

 wettable powder formulation of amitraz is underway at the 

 present time. 



The first year of funding for a 3-year pilot test of the sterile 

 hybrid male Boophilus eradication method became available 

 during FY 1987. When a lease agreement for pasture is 

 reached with the Government of the United States Virgin 

 Islands, the test will be initiated on St. Croix. A number of 

 significant technical problems, including how to distribute the 

 hybrid larvae, must be resolved if this technique is to become 

 a component of an eradication campaign. The pilot test will 

 provide an opportunity to resolve technical problems and to 

 assess the practical potential of the method. 



In spite of a variety of past attempts to determine the role of 

 white-tailed deer in the ecology of 6. annulatus, the degree to 

 which deer contribute to dissemination and maintenance of 

 this species has not been defined. Recent studies at Mission, 

 which involved the use of confined, but unrestrained, deer 

 infested repeatedly with 6. annulatus larvae, have further 

 elucidated this host-parasite relationship. Only 3 percent of 

 the larvae on deer survive to become engorged females. This 

 compares to 30 percent of those on cattle. Also, the engorged 

 females from the deer were significantly smaller than ticks 

 which engorged on cattle. If deer are restained and cannot 

 groom themselves, as hosts they are equally as suitable as 

 cattle. It appears that the grooming behavior of deer reduces 

 their importance as hosts of 6. annulatus. 



For the past year, U.S. Livestock Insect Research Laboratory 

 scientists have been collaborating with ARS colleagues at the 

 Insects Affecting Man and Animals Research Laboratory in 

 Gainsville, Florida, on the development of an improved 

 computer simulation of a Boophilus tick population model. 

 This model will contribute to the development and testing of 

 various eradication strategies, including the sterile hybrid male 

 Boophilus eradication technology. A number of investigations 

 to fill gaps in our knowledge of the ecology of Boophilus i\cks 

 are providing information to be used in the computer 

 simulation model. A 2-year field study of the effect of climate 

 on the development and survival of B. microplus, B. annulatus, 

 and hybrid Boophilus ticks is more than half completed. 

 Hybrid male Boophilus ticks derived from a cross between S. 

 annulatus males and 6. microplus females were equally 

 competitive or superior to 6. microplus males in studies of 

 mating competitiveness. Investigations of host-seeking 

 behavior demonstrated that within 4 days after hatching, over 



