Optimal Conditions for Diapause Survival of Aprostocetus fukutai, an Egg Parasitoid for Biological Control of Anoplophora chinensis
USDA-ARS Beneficial Insects Introduction Research Unit, Newark, DE 19713, USA
USDA-ARS European Biological Control Laboratory, 34980 Montferrier-sur-Lez, France
Department of Food, Environmental and Nutritional Sciences, University of Milan, 20122 Milan, Italy
Ferrero Hazelnut Company, 2100 Chitatskari, Georgia
USDA-ARS Invasive Species and Pollinator Health Research Unit, Albany, CA 94710, USA
Author to whom correspondence should be addressed.
Academic Editor: Lara Maistrello
Received: 22 May 2021 / Revised: 4 June 2021 / Accepted: 7 June 2021 / Published: 9 June 2021
Diapause is a critical state of an insect’s life cycle when it undergoes arrestment of growth and/or reproduction to survive adverse environmental conditions and/or food shortage. Aprostocetus fukutai is a specialist egg parasitoid of the citrus longhorned beetle, Anoplophora chinensis, a high-risk invasive woodboring pest. The parasitoid overwinters as diapausing mature larva in the host egg and emerges in early summer in synchrony with the egg-laying of A. chinensis. Here, we determined the optimal conditions for diapause survival of this parasitoid. We showed that the parasitoid had a low (36.7%) diapause survival rate inside host eggs laid on potted plants due to desiccation or tree wound defense response under semi-natural conditions. Under laboratory rearing conditions, when parasitized host eggs were extracted from wood, the parasitoid did not survive at low humidity (44% RH). Survival rate increased with humidity, reaching the highest at 100% RH. Survival rate also increased with increasing chilling period temperature from 2 to 12.5 °C. Post-diapause developmental time decreased with increased humidity or temperature, but the reproductive fitness of the parasitoid was not significantly affected by the temperature regimes. Overall, high humidity (100% RH) and mild temperatures (12.5 °C) are the most suitable survival conditions for the diapausing parasitoid and thus should be used in laboratory rearing.