Pollinator Habitat Conservation Along Roadways, Volume 1: Alaska (2023) / Chapter Skim
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Pages 93-126
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6-1 Chapter 6 Roadside Maintenance and Vegetation Management for Pollinators 6.1 Introduction Roadside vegetation management provides a safe driving environment, preserves infrastructure, and maintains a resilient plant community. Many departments of transportation (DOTs)
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-2 butterfly or other needed habitat is present at a roadside site within the known range of an imperiled pollinator species, there is a chance that the pollinator is also there and that management actions could result in direct mortality. It is useful, although difficult, to survey host plants for immature stages of butterflies prior to mowing or using herbicides (or proceeding with other management actions, such as prescribed grazing)
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-3 Table 6-1. Periods of imperiled pollinator activity to avoid when conducting maintenance activities in Alaska.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-4 6.3 Adjusting Maintenance Practices to Benefit Imperiled Pollinators 6.3.1 Common Roadside Vegetation Management Practices Mowing How Mowing Affects Pollinators Mowing is frequently used to maintain roadside vegetation, reduce occurrences of invasive weeds and woody plants, improve drivers' sight lines, allow vehicles to pull off, and reduce the risk of wildfires. Typically, vegetation in the recovery area (also known as the clear zone -- the band of vegetation directly adjacent to the pavement or shoulder where vehicles that have left the roadway can recover)
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-5 season (Valtonen et al.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-6 habitats. Litter removal (e.g., haying)
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-7 Adjust mowing height to a minimum height of 8 to 10 inches in areas with target butterfly host plants or bumble bee colonies in grass thatch, if mowing during the growing season. Mowing established vegetation at a height of 8 to 10 inches (or higher, if equipment allows; see Eco 1200 from MULAG (Steidle et al.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-8 production of the next generation of queen bumble bees. Mowing late in the season would prevent injury or destruction of the colony from use of the mower.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-9 Box 6-3. How Do Other Wildlife Respond to Maintenance Practices Designed to Help Pollinators?
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-10 Herbicide Application How Herbicide Applications Affect Pollinators Herbicides are used to control woody vegetation as well as target weed species and other undesirable plant species on roadsides. The control of noxious and many invasive weeds is critical in maintaining habitat for many imperiled pollinators (Schultz and Dlugosch 1999)
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-11 Table 6-2. This information is based primarily on the testing of adult honey bees ahead of pesticide registration; there is very little information available on herbicide toxicity to larval bees, wild bees, or adult or larval butterflies.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-12 Table 6-2. Herbicides used on roadsides and what is known of their potential direct toxicity to pollinators.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-13 Herbicide Ratinga Precautions for Use within Roadside Pollinator Habitatb Source Dicamba Moderately toxic to adult honey bees Do not apply to or allow to drift onto flowers in bloom (including weeds) AERU 2022 Dichlobenil Moderately toxic to adult honey bees Do not apply to or allow to drift onto flowers in bloom (including weeds)
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From page 106... ...
Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-14 Herbicide Ratinga Precautions for Use within Roadside Pollinator Habitatb Source Fosamine Practically non‐toxic to honey bees No bee precaution, except when required by the label or regulations AERU 2022 Glyphosate Moderately toxic to honey bee adults and their brood, with impacts on gut biota, navigation, and survival Do not apply to or allow to drift onto flowers in bloom (including weeds) University of California Statewide Integrated Pest Management Program 2022 Motta et al. 2018, 2020 Battisti et al. 2021 Halosulfuron‐methyl Practically non‐toxic to honey bees No bee precaution, except when required by the label or regulations AERU 2022 Imazapic Practically non‐toxic to honey bees No bee precaution, except when required by the label or regulations AERU 2022 Imazapyr Moderately toxic to honey bees upon ingestion Practically non‐toxic upon contact Toxic to butterflies exposed as larvae, including some imperiled species Do not apply to or allow to drift onto flowers in bloom (including weeds)
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-15 Herbicide Ratinga Precautions for Use within Roadside Pollinator Habitatb Source Metsulfuron‐Methyl Moderately toxic to honey bees Do not apply to or allow to drift onto flowers in bloom (including weeds) AERU 2022 Norflurazon Practically non‐toxic to honey bees No bee precaution, except when required by the label or regulations University of California Statewide Integrated Pest Management Program 2022 AERU 2022 Oryzalin Moderately toxic to honey bees Do not apply to or allow to drift onto flowers in bloom (including weeds)
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-16 Herbicide Ratinga Precautions for Use within Roadside Pollinator Habitatb Source Pyraflufen Practically non‐toxic to moderately toxic to honey bees Do not apply to or allow to drift onto flowers in bloom (including weeds) University of California Statewide Integrated Pest Management Program 2022 EFSA 2015 Rimsulfuron Moderately toxic to honey bees upon ingestion Practically non‐toxic upon contact Do not apply to or allow to drift onto flowers in bloom (including weeds)
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-17 Herbicide Ratinga Precautions for Use within Roadside Pollinator Habitatb Source Triclopyr Practically non‐toxic to honey bees Toxic to butterflies exposed as larvae, including some imperiled species Avoid regular/repeated use on flowering plants Make applications outside season when caterpillars are active (see Chapter 3 for adult and larval active periods by species) EPA 2017 Stark et al. 2012 a.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-18 Conservation practices that benefit pollinators broadly: Train the staff and contractors to recognize native plants as well as noxious and invasive weeds to reduce unintended damage to nontarget plants. Conducting training in weed identification, as well as using plant identification reference materials to recognize noxious and invasive weeds, will help distinguish such species from similar nontarget species.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-19 Avoid herbicide sprays when weather conditions increase drift (e.g., avoid wind speeds above 15 mph, and avoid applications during a temperature inversion)
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-20 Avoid the use of pre-emergent herbicides on areas where the seed bank might contain desirable native species. Native species can be beneficial to pollinators and other wildlife; therefore, choose other methods of weed suppression in areas with desirable species.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-21 Box 6-6. Current Herbicide Practices Used by DOTs Many of the practices to reduce herbicide risk to pollinators were commonly used by DOTs across the country.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-22 Box 6‐7. Adjusting Herbicide Practices to Support Monarch Butterflies One of the most iconic pollinator species, the monarch butterfly (Danaus plexippus) , is recognized and celebrated by people throughout North America.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-23 Conservation actions that support pollinators generally include: Feather or soften forest edges adjacent to the recovery area to create a transitional area between forests and grass (e.g., thin portions of the forest canopy along the edge next to grassy areas, removing undesirable or unhealthy trees)
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-24 Box 6-8. Current Brush Removal Practices by DOTs Most respondents reported using practices that minimize soil disturbance during brush removal.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-25 6.3.2 Less Common Roadside Vegetation Management Practices Haying In some states, landowners are permitted to cut and remove roadside vegetation for animal fodder. States might grant emergency hay permits under drought conditions, for example, or allow annual haying by adjacent landowners on certain roads throughout the growing season.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-26 It is best to avoid using natural enemies that have expanded their hosts to include native plants. This could reduce food sources and alter habitat quality for imperiled pollinators.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-27 Prescribed Fire Prescribed fire is used to manage roadside vegetation and rejuvenate plant diversity in some regions of the United States that have a history of natural fires. Prescribed fire can remove old vegetation to create room for new growth, can reduce the spread of some invasive plants, and can stimulate the seed germination of some wildflowers.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-28 plant diversity in this region. However, it is important to note that the timing can be in direct conflict with the activity of certain imperiled pollinator species.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-29 area. (Plants are more likely to be toxic when traffic levels exceed 20,000 cars per day.)
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-30 6.4 Case Studies 6.4.1 Adjusting Mowing Practices to Benefit Monarch Butterflies in Illinois The monarch butterfly (Danaus plexippus) is the official state insect of Illinois.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-31 allows native vegetation to emerge and flourish, with sagebrush (Artemisia tridentata) , greasewood (Sarcobatus vermiculatus)
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-32 reduce the attractiveness of the foreslope to Fender's blue butterfly by managing it so that Kincaid's lupine would not persist. Working with USFWS, Yamhill County developed a habitat conservation plan for Fender's blue butterfly and Kincaid's lupine.
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Chapter 6. Roadside Maintenance and Vegetation Management for Pollinators 6-33 Evaluating the Suitability of Roadway Corridors for Use by Monarch Butterflies: https://www.nap.edu/catalog/25693/evaluating‐the‐suitability‐of‐roadway‐corridors‐for‐use‐by‐monarch‐ butterflies and http://www.trb.org/Main/Blurbs/180186.aspx. Milkweed Recognition Guides: https://www.xerces.org/monarchs/roadsides.
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