Sprays and Dips of Shell Compound 4072 to Control Boophilus Ticks and Larvae of the Screw-Worm on Cattle12

Abstract

At Matamoros, Tamaulipas, Mexico, cattle naturally infested with the southern cattle tick, Boophilus microplus (Canestrini), were wounded and infested with larvae of the screw-worm, Cochliomyia hominivorax (Coquerel), for 4 days, and then sprayed with 0.05-0.25% Shell Compound 4072 (2-chloro-1-(2,4-dichlorophenyl) vinyl diethyl phosphate) or 0.25% coumaphos. Shell Compound 4072 at 0.2n and 0.25% killed screw-worm larvae of all ages; at 0.10 and 0.15% killed all 1-and 2-day-old larvae; and at 0.05% killed all 1-day-old larvae. Coumaphos killed all land 2-day-old larvae. Nymphal ticks removed from cattle at 1 day post treatment molted, but engorged and partially engorged females did not produce viable eggs. Cattle artificially infested with the southern cattle tick; the cattle tick, Loopholes annulatus (Say), and 1- and 2- day-old screw-worm larvae were used in 3 tests at Neva Laredo, Tamaulipas, to evaluate the effectiveness of 0.05-0.13% Shell Compound 4072 as dips and sprays. Concentrations of 0.1% or greater killed all screw-worm larvae; 0.05-0.08% killed all 1-day-old larvae but not all 2-day-old larvae. Effectiveness against Boophilus ticks was determined by (1) mortality of adults and molting of nymphs removed from cattle at 1, 2, and 7 days post treatment and (2) weight and hatch of eggs from females collected from stalls containing the cattle. All concentrations were highly effective against adult ticks. Some nymphs collected from cattle 1 and 2 days after treatment molted to adults, but none collected at 1 week molted. A few females collected from stalls 1-4 days after treatment laid eggs, and some eggs hatched. Generally, there appeared to be little difference in effectiveness of sprays or dips, or of these different concentrations of Shell Compound 4072, in control of both B. microplus and B. annulatus .