The effect of Tree of Heaven, Ailanthus altissima, water-soluble extract on the growth and development of fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae)

The interaction between invasive plant species and native insect species continues to be an area of extreme importance.   The invasive tree species, Ailanthus altissima (Tree of Heaven), has become well established in North America.  However, the impact of its leaf chemical composition on other species, particularly insect herbivores, has not been well established.  We examined the growth and development of fall armyworm (Spodoptera frugiperda) reared on artificial diets in the laboratory with and without water-soluble leaf extracts from A. altissima.  Laboratory reared fall armyworm larvae weights were taken 3 and 6 days post-introduction of the leaf extract to the artificial diet.  At 6 d larvae continuously exposed to the diet including A. altissima leaf extract (experimental) had a mean weight of 0.165 g (.004 g SEM) compared to control larvae at 0.242 g (.005 g SEM).  Pupae mean weights were determined to be 0.214 g (.002 g SEM) for control and 0.187 g (.002 g SEM) for the experimental larvae.  Median time to pupation and time to emergence was determined for each population.  The median time to pupation from introduction of treatment was 11 d for the control population and 16 d for the experimental population.  The median time for experimental adult moths to emerge (relative to the introduction of the treatment) was delayed by 3 d compared to the control population.  Survivorship based on emergence of adults was slightly reduced in the experimental population compared to the control.  Larvae feeding on leaf extract supplemented diets had reduced numbers entering pupation, however, the proportion of survivorship associated with the transition from potentially viable pupae to adult emergence was not significantly different between the two conditions.  In conclusion, the addition of water-soluble extract from A. altissima leaves had a negative impact on the growth and development of S. frugiperda.  Larvae and pupae weights were reduced in addition to a distinct slowing of the transition between lifecycle stages as compared to the control populations reared on artificial diet alone.  This suggests that water-soluble secondary metabolites, possibly including the known allelochemical, Ailanthone, within the leaves of A. altissima can have detrimental effects on insect herbivores.  Further studies will investigate the specific chemicals present in the water-soluble fraction of A. altissima.