Agronomy and Horticulture, Department of

 

Date of this Version

Spring 5-1-2012

Comments

A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Agronomy (Weed Science), Under the Supervision of Professor Stevan Z. Knezevic. Lincoln, Nebraska: May, 2012

Copyright (c) 2012 Ryan E. Rapp

Abstract

There are two biotypes of common reed, which includes the native common reed (Phragmites australis subsp. americanus) and non-native (invasive) common reed (Phragmites australis subsp. australis).The non-native biotype of common reed has invaded wetland habitats in many states of the US, including Nebraska.

Three studies, disking followed by herbicide, mowing followed by herbicide, and herbicide followed by mechanical treatment were initiated in 2008 in Nebraska. The objective was to evaluate common reed control along the Platte River using an integrated management. Herbicide followed by mechanical treatment had excellent control (≥92%) with all treatments except glyphosate applied in the summer of 2008 alone or followed by a mechanical treatment 817 DAT.

Field studies were conducted the Platte River with the objective to determine the effect of herbicide selection and timing of application on common reed. Three herbicides were applied at two rates and three growth stages of common reed. In general, common reed showed more tolerance to applications during vegetative stage, with control ratings increasing with later timings. Imazapyr provided the highest levels of control (≥92%) across all three timings, while imazamox provided the lowest level of control 60%).

Measurements of gas exchange and leaf area index were collected in undisturbed stands of both native and non-native common reed stands. Stomatal conductance and leaf assimilation on average was higher in native common reed than in non-native common reed. LAI in invasive common reed was dramatically larger on average. There was 243 mm year-1 estimated difference in transpiration with non-native common reed having a higher estimation of transpiration.

An economic analysis of common reed management options reflecting water savings and net return on investment was performed. Returns ranged from $1,326 to $4,235 per hectare over three years. Treatments of disking followed by herbicide tended to have the highest initial net return. All treatments provided a net gain return after 3 years of control of common reed.

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