Rearing of two predators, Thanasimus dubius and Temnochila virescens, for the biological control of Ips grandicollis in Australia

Abstract

AbstractRearing methods for two coleopterous predators, Thanasimus dubius and Temnochila virescens, imported into Australia for the biological control of Ips grandicollis, were developed. Bionomic data obtained from laboratory rearings between 1982–1987 showed that T. dubius eggs took about 7 days to hatch and that duration of the larval stage was about 42 days. Observations showed that T. dubius had a prolonged prepupal stage (x̄ = 56.4 days, range 14–274 days), which was probably non‐diapausal in nature. Mean adult longevity was 50 days (range 1–358 days). Temnochila virescens eggs took almost 9 days to hatch, and a lengthy larval stage (x̄ = 155.4 days, range 73–333 days) was observed. Mean duration of the pupal stage was 14 days (range 7–28 days). A long preoviposition period (x̄ = 141 days, range 47–206 days) was observed, and adults were very long‐lived (x̄ = 232.7 days, range 14–667 days). Capacity for increase (rc) calculated from rearing data suggested that numbers of T. dubius could be increased faster than T. virescens. Mortality between 1982–1987 averaged about 70% for both species. However, mortality of T. dubius in 1987 increased significantly, suggesting that inbreeding or other methodological factors could be responsible. A mass‐rearing method using Ips‐infested pine billets was developed as a cheaper alternative to laboratory rearing, and was shown to be effective in producing large numbers of insects for release.