Development and fecundity of Scymnus (Pullus) coniferarum, a potential biocontrol agent for hemlock woolly adegid

The hemlock woolly adelgid (HWA), Adelges tsugae Annand, is an invasive pest of eastern hemlock (Tsuga canadensis (L.) Carrière) in eastern North America. Scymnus (Pullus) coniferarum Crotch (Coleoptera: Coccinellidae) is a lady beetle that preys on HWA in the western U.S. and is absent from hemlock stands in the East. While its release seems to be of limited risk, more information is needed on the life history of S. coniferarum to determine if it will be a suitable biological control agent for HWA in the eastern US.  Our priorities are to examine how to best increase adult survivorship, egg production, and development in the lab.  In two studies, we evaluated the effect of temperature and photoperiod on beetle ovipostion and development. We compared S. coniferarum oviposition period and egg production in a temperature-only assessment, where a cohort of ovipositing females were kept at a constant 15°C, and another at 8°C. The results suggest that temperature has an influence on oviposition duration and egg yield. Females held at 8°C had a shorter oviposition period and laid fewer eggs than those stored at 15°C. A second photoperiod experiment was designed to determine the ideal lab conditions for optimal S. coniferarum oviposition and survival. Three growth chambers were set-up with three different temperature and photoperiod combinations; mimicking an accelerated version of the ambient environment in their native range in Seattle. Oviposition rates and developmental success were found to be higher among the cohort exposed to a higher temperature and longer day length.