Efficacy of Treatments against Garlic Mustard (Alliaria petiolata) and Effects on Forest Understory Plant Diversity

AbstractThe interactive effects of herbivory, exotic species, and other human-mediated changes to the biosphere are reducing species diversity and altering ecosystem services globally. In this study, we tested whether facilitation could be used as a management technique to restore a degraded northeast Wisconsin forest understory facing high white-tailed deer (Odocoileus virginianus) browse pressure and high abundance of the exotic herb garlic mustard [Alliaria petiolata (Bieb.) Cavara & Grande]. Specifically, we attempted to facilitate native understory restoration by planting or seeding native herbs into three different matrix densities of the native, browse-tolerant grass Virginia wildrye (Elymus virginicus L.), which were either protected from (fenced), or accessible to, deer browsing. Deer had minimal impacts on E. virginicus but significantly reduced the cover, survival, and flower production of white snakeroot [Ageratina altissima (L.) King & H.E. Robins.] transplants, largely independent of the density of E. virginicus plantings in open-access plots. In contrast, the richness and abundance of native-seeded species were not affected by deer access but were reduced by increasing E. virginicus densities. Alliaria petiolata cover was significantly higher in plots accessible to deer but declined significantly with increasing E. virginicus planting density in both open-access and fenced plots. These results were largely corroborated by results from an associated observational study, with the exception that natural E. virginicus stands supported slightly higher native-species richness than did adjacent areas lacking E. virginicus. Thus, although we found little support that establishing E. virginicus facilitated browse-susceptible native understory herbs during our short-term experimental study, restored E. virginicus successfully established, thereby increasing native species cover and significantly reducing the cover of the exotic A. petiolata. We suggest the planting of browse-tolerant native species, such as E. virginicus, as a viable restoration technique in heavily browsed, A. petiolata–invaded woodlands.

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Colonization and Effects of Garlic Mustard (Alliaria petiolata), European Buckthorn (Rhamnus cathartica), and Bell's Honeysuckle (Lonicera × bella) on Understory Plants After Five Decades in Southern Wisconsin Forests

Invasive Plant Science and Management ◽

10.1614/ipsm-d-10-00084.1 ◽

2011 ◽

Vol 4 (3) ◽

pp. 317-325 ◽

Cited By ~ 13

Author(s):

Thomas P. Rooney ◽

David A. Rogers

Keyword(s):

Invasive Species ◽

Plant Species ◽

Invasive Plants ◽

Alliaria Petiolata ◽

Species Density ◽

Forest Understory ◽

Time Lags ◽

Garlic Mustard ◽

Native Plant ◽

Measurable Effect

AbstractPreinvasion baseline data on entire communities are absent for most taxa in most places, and this limits our ability to connect long-term ecological changes to particular invasive species or invasion events. We obtained data on forest understory composition from 94 stands in the 1950s and again the 2000s. We recorded within-stand frequency of occurrence for garlic mustard, European buckthorn, and Bell's honeysuckle and identified changes in native plant species density in 20, 1-m2 quadrats in invaded and noninvaded stands. All three invasive species were absent from all study sites 50 yr ago, yet at least one was present in 77.7% of the stands by the 2000s. All three species were present in 14.9% of the stands. Garlic mustard and European buckthorn were found at 47.9% of resurveyed sites, and Bell's honeysuckle was found in 40.4% of resurveyed sites. Native understory plant species density declined an average of 23.1% during the past 50 yr. Declines were not significantly different in stands with or without invasive plants. The absence of a measurable effect by invasive plant presence or frequency could be due to invasive plants being too few to have a measurable effect at the plot scale, species density being an insensitive response variable, time lags between invasions and effects, or regional factors like development pressure and fire suppression driving density declines in both invasives and native species.

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A multifaceted approach for beech forest conservation: Environmental drivers of understory plant diversity

Flora ◽

10.1016/j.flora.2019.05.006 ◽

2019 ◽

Vol 256 ◽

pp. 85-91 ◽

Cited By ~ 3

Author(s):

Gianluigi Ottaviani ◽

Lars Götzenberger ◽

Giovanni Bacaro ◽

Alessandro Chiarucci ◽

Francesco de Bello ◽

...

Keyword(s):

Plant Diversity ◽

Forest Conservation ◽

Beech Forest ◽

Environmental Drivers ◽

Multifaceted Approach ◽

Understory Plant

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Do applications of systemic herbicides when green fruit are present prevent seed production or viability of Alliaria petiolata (garlic mustard)?

Invasive Plant Science and Management ◽

10.1017/inp.2021.8 ◽

2021 ◽

pp. 1-17

Author(s):

Leo Roth ◽

José Luiz C. S. Dias ◽

Christopher Evans ◽

Kevin Rohling ◽

Mark Renz

Keyword(s):

Seed Production ◽

Seed Viability ◽

Early Spring ◽

Alliaria Petiolata ◽

Late Spring ◽

Garlic Mustard ◽

Viable Seed ◽

Application Timing ◽

Control Seed ◽

Second Year

Garlic mustard [Alliaria petiolata (M. Bieb.) Cavara & Grande] is a biennial invasive plant commonly found in the northeastern and midwestern United States. Although it is not recommended to apply herbicides after flowering, land managers frequently desire to conduct management during this timing. We applied glyphosate and triclopyr (3% v/v and 1% v/v using 31.8% and 39.8% acid equivalent formulations, respectively) postemergence to established, second-year A. petiolata populations at three locations when petals were dehiscing, and evaluated control, seed production and seed viability. Postemergence glyphosate applications at this timing provided 100% control of A. petiolata by 4 weeks after treatment at all locations whereas triclopyr efficacy was variable, providing 38-62% control. Seed production was only reduced at one location, with similar results regardless of treatment. Percent seed viability was also reduced, and when combined with reductions in seed production, we found a 71-99% reduction in number of viable seed produced plant-1 regardless of treatment. While applications did not eliminate viable seed production, our findings indicate that glyphosate and triclopyr applied while petals were dehiscing is a viable alternative to cutting or hand-pulling at this timing as it substantially decreased viable A. petiolata seed production. Management Implications Postemergence glyphosate and triclopyr applications in the early spring to rosettes are standard treatments used to manage A. petiolata. However, weather and other priorities limit the window for management, forcing field practitioners to utilize more labor-intensive methods such as hand-pulling. It is not known how late in the development of A. petiolata these herbicides can be applied to prevent viable seed production. Since prevention of soil seedbank replenishment is a key management factor for effective long-term control of biennial invasive species, we hypothesized late spring foliar herbicide applications to second year A. petiolata plants when flower petals were dehiscing could be an effective management tool if seed production or viability is eliminated. Our study indicated that glyphosate applications at this timing provided 100% control of A. petiolata plants by 4 weeks after treatment at all locations, whereas triclopyr efficacy was inconsistent. Although both glyphosate and triclopyr decreased viable seed production to nearly zero at one of our three study locations, the same treatments produced significant amounts of viable seed at the other two locations. Our findings suggest late spring glyphosate and triclopyr applications should not be recommended over early spring applications to rosettes for A. petiolata management, as our late spring application timing did not prevent viable seed production, and may require multiple years of implementation to eradicate populations. Nonetheless, this application timing holds value in areas devoid of desirable understory vegetation compared to no management practices or mechanical management options including hand-pulling when fruit are present, as overall viable seed production was reduced to similar levels as these treatments.

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