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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Invasive Species and Pollinator Health » Research » Research Project #429326

Research Project: Improving Chemical Control of Flowering Rush Using Phenological Weak Points

Location: Invasive Species and Pollinator Health

Project Number: 2030-22000-030-02-I
Project Type: Interagency Reimbursable Agreement

Start Date: Aug 1, 2015
End Date: Dec 31, 2018

The objectives of this work will involve two phases: 1) examine growth and carbohydrate storage of diploid and triploid populations of flowering rush in mesocosm systems to determine phenological weak-points for improved chemical control techniques; and 2) evaluate efficacy of chemical management strategies under field conditions in the Pacific Northwest, based on results of the phenological work.

1) Growth and Carbohydrate Experiment. Plants will be collected from Western locations of both diploid and triploid flowering rush populations, in an outdoor mesocosm experiment at the USDA-ARS Aquatic Weed Research Laboratory at UC-Davis. Three 8-ft diameter tanks will be used for each population type, for a total of twelve tanks. Seventy-two (72) one gallon pots will be planted with the appropriate population, two rhizomes per pot, amended with fertilizer. Plants will be allowed to grow for three to nine months before initiating sampling events. Plants will be harvested monthly and sorted by above and belowground tissue, rhizomes, inflorescences, and bulbils to determine biomass levels of each tissue type. These tissues will be processed and analyzed for carbohydrate content, as a marker for phenological weak points in the growth cycle. In addition, degree-days (used to model growth), relative growth rate, and developmental stages of plants will be assessed. The growth rate of the populations will be compared statistically to determine if there is any difference in growth between diploid and triploid populations. (2) Field Efficacy of Herbicide Treatments. Herbicide evaluations will focus on applications to selected de-watered sites on Lake Pend Oreille, ID, (a CE Project) in 2015. These sites contain flowering rush populations of various sizes in up to 10 feet of water at full-pool lake elevation. Treatment plots will be 1 surface acre in size, and replicated three times for each application, including untreated reference plots. Treatments will be conducted on de-watered (dry) sites in April/May, once young shoots have emerged from the de-watered sediment. Herbicides to be evaluated will include imazamox, imazapyr, 2,4-D, tank mixed with an aquatic surfactant. Quantitative assessments of the vegetative community, using point intercept techniques, will be conducted at pretreatment, and 6-8 weeks posttreatment, and one and two years posttreatment (pending funding). Plant sampling will be used to assess changes in above and belowground biomass, and rhizome bud density. These assessments will be performed across three growing seasons (2015-17), and will be used to determine treatment efficacy against flowering rush, and any impacts on the non-target plants within the site.