Garlic mustard, Alliaria petiolata, has invaded forests throughout eastern North America. In 1998, researchers initiated a biological control program and have identified several Ceutorhynchus weevils as potential control agents. To investigate the potential impacts of introduced natural enemies we studied relationships between garlic mustard population density and plant biology, emphasizing plant characteristics impacted by potential control agents. Using life table analysis, we investigated survivorship and reproduction in low- and high-density garlic mustard populations. We also simulated insect damage to study potential responses of the plant to herbivory, specifically the impact of manual flower shoot damage (shoots cut at tip or base) upon plant development and reproduction. Lastly, we studied the response of second-year rosettes to experimental reductions in plant density.
In the life table study, the low density population had a higher intrinsic growth rate than the high density population (r=0.34 and 0.08, respectively) due to greater survival (low: 88%, high: 75%) and seed production (low: 437.51 ± 63.73SE, high: 305.27 ± 49.93SE). In the flower shoot damage experiment, treatment significantly affected plant survival (P<0.0001). All plants in un-cut and tip-cut treatments survived to reproduction, but only 27.5% of basal-cut plants survived. Basal-cut plants produced 94% less seed than un-cut plants, resulting in negative population growth. Lastly, manual density reduction negatively impacted net reproduction and population growth rates. Taken together, our studies suggest a significant potential for biological control, particularly with agents that reduce plant density or that damage the growing point of the plant.
Species 1: Capparales Brassicaceae Alliaria petiolata (garlic mustard)
Keywords: weed biological control
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