The effect of manual defoliation and Macaria pallidata (Geometridae) herbivory on Mimosa pigra: Implications for biological control

Trials were conducted to test the effects of artificial defoliation and defoliation by Macaria pallidata (Warren) (Geometridae) larvae on the invasive weed Mimosa pigra L. Herbivory is generally thought to be detrimental to plant fitness but it is well documented that many plants can increase growth rates or reproduction to compensate for damage. The compensatory ability of an invasive plant has implications for the potential success of defoliating biocontrol agents. Mimosa compensated for 25% manual defoliation, but at 50% and 100% defoliation levels plants suffered a significant reduction in growth rate, height, stem diameter, and biomass. Defoliation by one cohort of macaria larvae, at densities of eight larvae per plant, significantly reduced growth rates and plant height after 1 week. There were no differences between the effects of macaria larvae and manually simulated defoliation. These results suggest that defoliating biocontrol agents can have a valuable role in mimosa control programs.