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Garlic mustard

Kyle Burns, Tyler McPheters, Ashley Paschal, and Brian Scott
Conservation Biology, BIO 345, Biology Department, DePauw University
Spring semester 2006

Invasive plants are a major ecological concern, and their successful management is vital for the sustaining ecosystem integrity and biodiversity.  Garlic mustard is a non-native invasive plant species in deciduous forests with few natural threats from herbivores.  Biological controls, however, may be an effective and environmentally sound way to eradicate garlic mustard.  Simulated herbivory is a suitable way to study the effects of herbivory on plant growth and reproduction. 

We hypothesized that simulated herbivory would reduce the survival, growth, and reproduction of garlic mustard. 

We set up 40 plots in dense patches of garlic mustard along the Creekside Trail in the DePauw Nature Park.  Each plot contained at least three garlic mustard plants.  Within each plot, we labeled one plant as control, one plant as low herbivory, and one plant as high herbivory.  We counted the number of leaves on each plant.  We used a standard hole puncher to simulate herbivory.  In the low herbivory treatment, we removed one fourth of the leaf area.  In the high herbivory treatment, we removed half of the leaf area.  We measured light intensity, soil moisture levels, number of flowers, height of plants, and above-ground biomass of plants. 

Our simulated herbivory treatments had no effect on the height, biomass, or number of flowers of garlic mustard plants.  The height of the plants was correlated with the number of flowers and biomass of the plants.  There was also a correlation between initial number of leaves and amount of sunlight. 

Our herbivory treatments were ineffective at controlling the growth and reproduction of garlic mustard.  Our results indicate that herbivores must inflict a large amount of damage to have an effect on garlic mustard.  Due to its resilience against herbivory, garlic mustard deserves a great deal of attention and might require more swift means of eradication than herbivory.  Other strategies to control garlic mustard include pulling and removing the plants, herbicide application, and controlled burns.  Small isolated patches of garlic mustard should be controlled to prevent the plant from spreading.