Seasonal Activity, Within-Tree Distribution, and Ovipositional and Feeding Preference of the Elm Leafminer, Fenusa ulmi (Hymenoptera: Tenthredinidae)

Abstract

Seventy-six different elm taxa were visually rated for elm leafminer (Fenusa ulmi Sundevall) defoliation. European elm taxa were more found to be more susceptible to feeding damage by the elm leafminer compared to Asian and North American elm taxa. European elms U. glabra, U. elliptica, U. sukaczezii, and elms with U. glabra-wallichiana parentage were highly susceptible to elm leafminer leaf feeding damage. Of the 37 Asian elm taxa evaluated, only U. laciniata was highly susceptible to feeding damage. The North American species U. rubra was the only North American elm susceptible to elm leafminer feeding. Adult emergence, initial leafmining, and cessation of leafmining were highly correlated with indicator plant full bloom phenology providing an accurate degree-day (DD) model for practitioners in predicting and monitoring for elm leafminer life stage development and related plant damage. Elm leafing out phenology of susceptible European elms was highly correlated with elm leafminer adult emergence and oviposition. Less susceptible European elm taxa, such as U. procera, and U. carpinifolia and cultivars, consistently leaf out later after peak adult leafminer emergence. Interestingly, the majority of Asian elm taxa such as U. davidiana, U. japonica, U. lamellosa, and U. pumila leaf out at the same time as susceptible elm taxa, but experience no or negligible feeding damage. Two Asian species, U. wilsoniana and U. parvifolia, leaf out later after peak adult emergence and oviposition has passed. No consistent pattern was observed for within tree ovipositional wounds and subsequent leafminer feeding damage for tree height or cardinal direction for both small and large elm tree species. Results from this study indicate there is a large number of Asian and North American elm taxa that provide a rich genetic pool for future elm breeding programs.