Mortality factors associated with laboratory reared Douglas-fir tussock moth larvae : a case study

In conjunction with a proposed suppression project against the Douglas-fir tussock moth\ud in northern Idaho, more than 1,000 larvae were collected from sample plots throughout\ud the 32,000-acre treatment area. We had hoped to determine naturally occurring mortality factors which may have contributed to lower than anticipated population levels. Reared\ud on artificial media, 71.5 percent of the larvae completed their development to the adult\ud stage. Parasites accounted for 10.6 percent of the pre-adult mortality, native NPV only\ud 3.1 percent; 12.9 percent died of other diseases or unknown causes. No single factor was\ud identified as having resulted in unexpectedly low tussock moth populations in 1986