Towards pheromone-based monitoring of nun moth, Lymantria monacha (L.) (Lep., Lymantriidae) populations

The research objective was to develop pheromone-based monitoring of the nun moth, Lymantria monacha (L.), an important defoliator of spruce and pine forests in central Europe. In 38 spruce or pine forests in central Europe, captures of male L. monacha in nonsaturating Unitraps and saturating Delta sticky traps baited with 0.2, 2, 20, or 200 mu g of the L. monacha (pheromone) volatile blend [(+/-)-disparlure, (+/-)-monachalure, and 2-methyl-Z7-octadecene at a 20:20: 1 ratio] were compared with estimates of population densities obtained by counts of larval faecal pellets, pupal cases, and adult moths resting on tree trunks. Total captures of male L. monacha throughout the flight season in both types of trap were correlated with numbers of larval faecal pellets, irrespective of pheromone dose. Nonsaturating Unitraps baited with 2 mu g of the L. monacha volatile blend seem to provide a cost-effective tool for monitoring densities of L. monacha populations. Long-term testing of this monitoring system has been initiated to substantiate the quantitative relationship between larval populations and trap captures of male L. monacha and to determine the threshold number of captured male moths that indicates an incipient outbreak.