Five Years of Continuous Thaumetopoea processionea Monitoring: Tracing Population Dynamics in an Arable Landscape of South-Western Germany

Within this paper we summarize the results of the Thaumetopoea processionea monitoring at two observation sites and try to interpret population dynamics from 2006 to 2010 considering meteorological data. Furthermore, observations on the behaviour of neonates associated with oak budburst are presented and discussed. In 2007 large larval colonies occurred and population densities peaked. Massive defoliation and larval migration due to food shortage were observed regularly leading to reduced female moth fecundity. Unfavourable weather conditions probably abetted OPM population decline in spring 2008. Additionally oak budburst was delayed remarkably. More detailed observations on the hatching process and the behaviour of single colonies revealed increasing mortality after two and a half weeks of starvation. The 2009 results indicated another increase of population densities, but exceeded cool and humid weather conditions in May 2010 presumably prevented a new OPM outbreak. In accordance with previous studies egg parasitisation seems to play a minor role in OPM population dynamics.     

Temporal synchrony of Thaumetopoea processionea egg hatch and Quercus robur budburst

Field observations on egg hatch of Thaumetopoea processionea suggest that temporal asynchrony with Quercus robur budburst leads to starvation, retarded neonate development and mortality. However, T. processionea neonates are generally well adapted to variable between-tree and within-tree budburst phenology reflecting the species’ close bond to its host. They are able to withstand starvation periods of up to 3 weeks while searching extensively for suitable buds to feed on. Feeding and movements of young larvae frequently occur during daytime presumably taking advantage of higher day temperatures when night temperatures are below the species’ thermal threshold. Due to the specific adaptations, we assume precise temporal synchrony to play a minor role regarding its influences on T. processionea population dynamics. However, if hatching precedes budburst for more than 2–3 weeks, temporal asynchrony may become a significant mortality factor for the neonates particularly when other adverse events (e.g. unfavourable weather conditions) during that period are involved. Therefore, future studies should try to reveal further details of this interaction and focus on the impact of global warming on T. processionea—oak budburst synchronisation.     

Aerial Spraying of Neemazal®-T/S Against the Forest Cockchafer (Melolontha hippocastani,Col.: Scarabaeidae) in South-West Germany: The Effects of Two Field Trials Performed in 2007 and 2008 on Local Populations

Journal of Plant Diseases and Protection - The forest cockchafer Melolontha hippocastani is a serious forest pest whose infestation levels have been increasing in South-West Germany since the...