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Abstract:
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The biennial plant garlic mustard or Alliaria petiolata is a European native that is invasive in North America. The objective is to examine the effects of the defense hormones salicylic acid and jasmonic acid on defensive chemistry and insect performance on two populations of garlic mustard. The treatments included an independent treatment of each hormone, a control, and a combined treatment of both hormones to see if they acted synergistically or antagonistically. The effects of the hormones on the plants were measured by performance of a chewing herbivore, aphids, insect growth as well as biochemical changes of the plant. Results have indicated Pieres repae larvae tend to have a higher survival rate on the combined treatment of jasmonic acid and salicylic acid when compared to all the other hormone treatments for both populations. The jasmonic acid treatment had the lowest survival rates compared to the other treatments in both populations. Aphid damage results indicate that the combined treatment again had the most aphid damage in both populations. Therefore, the combined treatment could make the plant more palatable for the Pieres repae larvae. The growth rate for the combined treatment was smaller compared to the other treatments for both populations. The growth rates are not only caused by the hormone treatment, but the aphid damage to the plant. Cyanide assay results indicate that the salicylic acid treatment and the combined treatment had the highest concentrations of cyanide. The higher concentration of cyanide might suggest a better defense mechanism needed for these groups of plants. Other defense chemistry assays will be performed on the plants. |
