ABSTRACT The Eucalyptus variegated beetle ( Paropsisterna cloelia ) was established in New Zealand in 2016 and has caused substantial damage to selected host species. Previous field observations suggested that Pst. cloelia larvae may feed for a longer period during the year than the closely related Eucalyptus tortoise beetle ( Paropsis charybdis ), New Zealand's current most damaging eucalypt defoliator. Phenology and voltinism of these two invasive paropsine leaf beetles were quantified over two eucalypt growing seasons at two sites planted with Eucalyptus bosistoana in Marlborough, New Zealand. Results show that the availability of new foliage determined the voltinism and phenology of P. charybdis and Pst. cloelia and that the phenology of both species coincided at both field sites. As the availability of new leaves in spring and mid‐summer prompts oviposition, both species had two generations at the site where trees produced new leaves in spring and mid‐summer and one generation at the site where trees only produced new leaves in spring. Additionally, field observations indicate that both species have the potential for a third generation if the growing season is extended and trees produce new foliage three times. These conditions may be met in the Northland and coastal Bay of Plenty regions. Consequently, we conclude that Pst. cloelia does not produce more generations than P. charybdis and that larval activity coincided during the sampling seasons. Pst. cloelia is expected to spread throughout New Zealand over time and may become as damaging as P. charybdis on its preferred eucalypt hosts. We suggest future research to quantify phenology and voltinism of both species in warm/wet regions of New Zealand, to establish development models to inform pest management and to define host preferences for risk assessment.
Weser et al. (Fri,) studied this question.