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United States Department of Agriculture

Agricultural Research Service

Research Project: Aquatic and Riparian Weed Management to Protect U.S. Water Resources in the Far West United States

Location: Exotic and Invasive Weeds Research

Title: Impacts of mowing and bud destruction on Centaurea solstitialis growth, flowering, root dynamics and soil moisture

Authors
item Spencer, David
item Enloe, Stephen -
item Pitcairn, Michael -
item Di Tomaso, Joseph -

Submitted to: Weed Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 12, 2013
Publication Date: April 1, 2014
Citation: Spencer, D.F., Enloe, S.F., Pitcairn, M.J., Di Tomaso, J.M. 2014. Impacts of mowing and bud destruction on Centaurea solstitialis growth, flowering, root dynamics and soil moisture. Weed Research. 54:140-150.

Interpretive Summary: Yellow starthistle has invaded western grasslands within the last 100 years. For two control measures, mowing and biological control, evidence suggests that mowing is more effective at reducing growth and seed production. We conducted an experiment to test this hypothesis. We chose two treatments (late spring and early summer bud destruction and shoot mowing) and measured yellow starthistle’s growth and reproduction. We also measured changes in soil moisture content to test the hypothesis that these management approaches affect soil moisture differently. Mowing produced shorter plants that weighed less, while bud damage reduced plant height and weight only slightly. The number of developed seed heads was reduced 67% by mowing but was not affected by bud damage. Mowed plants transferred resources from root to flower production. Both treatments reduced mean seed head diameter. This resulted in reductions of 76% and 21% in estimated seed number for mowed and bud damaged plants, respectively. Root abundance decreased and root longevity was reduced by both treatments. Soil moisture depletion was greatest from mid-May through mid-July (from 21% to 9%), and occurred mainly after root abundance reached its maximum. Mowing resulted in a delay in soil moisture depletion compared to bud damage and the untreated control. It appears damage similar to that caused by biological control agents does not reduce yellow starthistle’s requirement for soil water as much as mowing does. Overall, this study demonstrated that mowing reduced yellow starthistle growth and reproduction more than bud damage. This information will aid managers in selecting the appropriate strategy for managing yellow starthistle in a particular habitat.

Technical Abstract: Yellow starthistle (Centaurea solstitialis) occurs in rangelands and natural areas in the western USA. For two control measures, mowing and biological control, evidence suggests the hypothesis that mowing is more effective at reducing growth and seed production. We conducted an experiment to test this hypothesis. We chose two treatments (late spring and early summer bud destruction and shoot mowing) and measured yellow starthistle’s growth and reproduction. We also measured changes in soil moisture content to test the hypothesis that these management approaches differentially affect soil moisture. Mowing produced shorter plants that weighed less, while bud damage reduced plant height and weight only slightly. The number of developed capitula was reduced 67% by mowing but was not affected by bud damage. Mowed plants redistributed resources from root to flower production. Both treatments reduced mean capitula diameter. This resulted in reductions of 76% and 21% in estimated seed number for defoliated and bud damaged plants, respectively. Root abundance decreased and root longevity was reduced by both treatments. Soil moisture depletion was greatest from mid-May through mid-July (from 21% to 9%), and occurred mainly after root abundance reached its maximum. Mowing resulted in a temporal delay in soil moisture depletion compared to bud damage and the untreated control. It appears damage similar to that caused by biological control agents does not affect yellow starthistle’s requirement for soil water. Overall, this study demonstrated that mowing reduced yellow starthistle growth and reproduction more than bud damage. This information will aid managers in selecting the appropriate strategy for managing yellow starthistle in a particular habitat.

Last Modified: 7/25/2014
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