Biological parameters of ticks (Amblyomma cajennense Fabricius, 1787) under field and laboratory conditions in Pedro Leopoldo, State of Minas Gerais, Brazil.

This study evaluated the biological parameters of the duration of the pre-oviposition and egg incubation periods and maximum survival of unfed larvae, under field and laboratory conditions, with the aim of providing support for more rational measures for controlling Amblyomma cajennense. This study was conducted at the Experimental Farm of the Veterinary School of the Federal University of Minas Gerais. Every 14 days, from September 1997 to March 1998 and from October 1998 to April 1999, six netted tubes containing engorged females were kept on pasture of Brachiaria decumbens that was up to 60 cm high and another six were kept in a BOD glass chamber (27 degrees C, 80% relative humidity). For both groups, 84 and 72 females were used during the first and second observation periods, respectively. The duration of the pre-oviposition period was similar under both conditions (5-7 days). Significant differences were seen between the duration of the egg incubation period under field conditions (56 to 60 days) and under BOD conditions (34 to 39 days); and between the maximum survival of the unfed larvae under field conditions (14 months) and under BOD conditions (9.5 months). These suggest that behavioral diapause was occurring. The long survival of unfed larvae in pasture needs to be considered when implementing Amblyomma cajennense control programs.