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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGY AND MANAGEMENT OF INVASIVE WEEDS IN THE WESTERN UNITED STATES Title: Integrated management of Scotch broom, Cytisus scoparius: is control enhanced when seed predation is combined with prescribed fire or mowing?

Authors
item Reddy, Angelica
item Carruthers, Raymond
item Mills, Nick -

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 13, 2010
Publication Date: N/A

Interpretive Summary: Integrated weed management (IWM) strategies are being advocated and employed to control invasive plants species. Prescribed fire, mechanical removal, and biological control by a beetle seed predator (Exapion fuscirostre) are used to manage Scotch broom (Cytisus scoparius) in prairies at Fort Lewis, Washington. In this study, we compared three management strategies [biological control alone (BC), BC with fire (BC + F), and BC with mowing (BC + M)] to determine if combining fire or mowing with biological control improves the control of Scotch broom. We measured seed production by Scotch broom and beetle seed predation at both the pod and plant scale, and seed bank density over two field seasons. There was no difference in the number of seeds per pod among management strategies. However, both the BC + M and BC + F plots contained fewer pods per plant, fewer mature seeds per plant, and a greater reduction in the number of seeds per meter square in the soil than BC plots. We found no difference among the three management strategies in the number of beetles per pod or the number of seeds predated by the beetle per pod or plant. While both integrated management strategies seemed to outperformed BC alone in reducing seed production and the seed bank, we propose that prescribed burning may be a more effective strategy for long term control of Scotch broom.

Technical Abstract: Integrated weed management (IWM) strategies are being advocated and employed to control invasive plants species. Prescribed fire, mechanical removal, and biological control (seed predator Exapion fuscirostre) are used to manage the invasive plant, Cytisus scoparius, in prairies at Fort Lewis, Washington. In this study, we compared the impact of three management strategies [biological control alone (BC), BC with fire (BC + F), and BC with mowing (BC + M)] to determine if combining fire or mowing with biological control enhances control of C. scoparius. We measured seed production by C. scoparius and seed predation by E. fuscirostre at both the pod and plant scale, and seed bank density over two field seasons in replicated field plots. There was no difference in the number of seeds per pod among management strategies. However, there were 71% fewer pods per plant, 79% fewer mature seeds per plant, and an 82% reduction in seed bank density in the BC + M plots, and 55% fewer pods per plant, 69% fewer mature seeds per plant, and a 93% reduction in seed bank density in the BC + F plots compared to the BC alone plots. We found no difference among management strategies in the number of E. fuscirostre per pod or the proportion of seeds predated by E. fuscirostre at either the pod or whole plant scale. While both integrated management strategies outperformed BC alone in reducing seed production and the seed bank, with no statistical difference between them, we propose that short-rotation prescribed fire may prove to be the more effective strategy for long-term management of C. scoparius as its potential for slightly greater depletion of the seed bank.

Last Modified: 10/31/2014
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