Infestations of winter ticks, Dermacentor albipictus (Packard), observed on mature black Angus cows, reached peak levels in January and diminished through March. Infestations of adult lone star ticks, Amblyomma americanum (L.), began in mid-January and increased through May. Cows receiving Ectrin, Taktic, or Deltox treatments on 13 December and 21 February experienced significantly less weight loss and entered the subsequent breeding season with higher average body weight than untreated cows. In a separate study, lactating Brangus and Brangus-cross cows, equally infested by natural populations of these ticks, were provided five supplement treatment regimens, fed individually with quantities adjusted for body weight and condition score. Groups receiving supplementation highest in crude protein and digestible energy lost significantly less weight and experienced the least amount of deterioration in body condition. Performance among these groups was influenced by the amount of digestible energy and the period in which increased levels of digestible energy were fed. Cows receiving the supplement highest in protein coupled with an increase in digestible energy from 10 to 60 Mcal/kg W0.75 on 16 January experienced the smallest average change in condition score and weight parameters.
A greenhouse study was conducted to measure the spatial distribution and behavior of third instar larvae on amitraz (ATZ)-treated and untreated plants. TBW eggs were obtained from ICI Americas' cypermethrin-resistant (R) and -susceptible cultures. Neonate larvae were placed on pinto bean diet in plastic cups and held in an incubator at 27 ± 2°C with a 12:12 (L:D) photoperiod until they reached third instar. Squaring cotton was sprayed with aqueous dilutions of ATZ using a CO2 pressurized (40 psi) backpack sprayer calibrated to deliver 4.4 gal/acre through 2, size 3X hollow-cone nozzles per row. The third instars were placed on the third mainstem internode below the shoot terminal of each plant 1 h following application of ATZ. Treatments were placed randomly in the greenhouse. Larval location and activity were observed on each plant at 15 min intervals for 6 h or until the larva left the plant. Locations recorded were shoot terminals, squares, leaf blades and stem/petioles. Vertical migration of the larva was measured by recording the number of the mainstem internode from which the plant structure arose where the larva was located. Feeding/scraping, resting, locomotion and spin-down were the larval behaviors recorded. The 6 treatments were replicated 20 times. The percent occurrence of each larva at each location, and larval behavior at each location for the 6-h observation period was a replicate.
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