Impact of the shoot-boring moth Dichrorampha odorata (Lepidoptera: Tortricidae) on growth and reproductive potential of Chromolaena odorata (Asteraceae) in the laboratory

A 9-month laboratory study was carried out to determine the impact of herbivory by a moth with shoot-boring larvae, Dichrorampha odorata Brown and Zachariades (Lepidoptera: Tortricidae) on growth and reproductive ability of its host plant, Chromolaena odorata (L.) King and Robinson (Asteraceae), a major invasive alien plant species in southern Africa. Newly hatched D. odorata larvae were inoculated onto 0 (control), 50 and 100% of the shoot tips of C. odorata in the laboratory. At all treatment levels, the basal stem diameter of C. odorata was not affected by D. odorata larval feeding. Larval feeding by D. odorata significantly reduced the height of the main shoot and flower production in C. odorata relative to the control treatment but promoted branching by increasing the number of shoot tips. However, the differences in plant height and number of flowers between the 50 and 100% inoculation levels were not statistically significant. Dichrorampha odorata is the first shoot-tip attacking agent that is being released as a biological control agent against C. odorata in South Africa. In general, the impacts of D. odorata on the weed were relatively small even though statistically significant. The findings of this study suggest that high levels of damage by the moth will modestly reduce the height, flower production, and the competitiveness of C. odorata, thereby contributing to the biological control of the weed in South Africa.