Invasive Plants and Noxious Weeds: Identification and Management

Transcription

1 Invasive Plants and Noxious Weeds: Identification and Management Sasha Shaw King County Noxious Weed Control Program

2 Agenda Brief review of definitions, lists and impacts Biology and control of common invasive plants and noxious weeds Early detection training for less common noxious weeds IPM for managing noxious weeds in natural areas Methods for staff and volunteers Field trip to Kiwanis Ravine (two stops)

3 What is an Invasive Plant? Successful invader Introduced from elsewhere, non-native Escapes into natural areas Persists and spreads Generally lacks predators and natural controls Causes harm Disrupts ecosystems Out-grows, out-spreads and out-competes native plants Invasive plants such as English ivy displace native plants and wildlife and can transform entire ecosystems

4 How bad is the problem in our cities? Seattle has ~8,000 acres of public land Invasive non-native plant species are present in 94% of these urban natural areas 20% of the city s forested areas are highly invaded by a suite of invasive species Percent cover of invasive species present in Seattle's urban forests Very High (>100%) High (81-100%) Moderately High (51-80%) 9% 18% 20% 11% 17% Trace (0-10%) 25% Medium (31-50%) Low (11-30%) In 47% of Seattle s forests, the majority of the plant cover consists of invasive species

5 Sources of Introduction Intentional (accidentally on purpose) Ornamental planting Crops Erosion control Accidental Ballast material Contaminant Seeds Hay Live plants Ornamental escapee Ship ballast and ornamental escapee Erosion control Seed and hay contaminant

6 Dispersal Methods Natural Processes Wind Water/flooding Birds and other animals Human Causes Hitchhiking on vehicles, boots, boats, etc Construction/Grading Mowing/Equipment Yard waste dumping Being planted

7 What is a Noxious Weed? Legal term, defined and regulated by Washington State law (RCW 17.10) Non-native plant that impacts agriculture, wildlife, human health, land values or natural resources Private and public property owners are required to control selected weeds Goal of law is to prevent spread of new invaders to uninfested areas Weeds are regulated only where they are not widespread Regulated at the county level; lists and priorities vary by county Not all invasive weeds are on the noxious weed list and not all noxious weeds impact natural areas

8 Invasive Plants Noxious Weeds Ecologically-based concept Legal, policy-based concept

9 One Law, Two Lists (both covered under RCW 17.10) Noxious Weed List (WAC ) Dictates which weeds need to be controlled statewide or in particular counties or regions Weeds are regulated where they are beginning to invade but not yet widespread or according to county priorities Updated annually by the State Weed Board, administered by county noxious weed boards Each county has its own weed list set by the county weed board County lists can include more but not fewer noxious weeds than required by the state State Prohibited Plants List (WAC ) Determines what can t be sold (quarantine list) Administered by WSDA Nursery Inspection Program Goal is to prevent introduction of new weeds

10 What are the Categories on the King County Weed List? Class A Weeds new invaders, control required statewide, still a chance to eradicate Examples: garlic mustard, giant hogweed Class B and C Regulated Weeds control required in King County, still have a chance to stop them from getting established Examples: garden loosestrife, policeman s helmet Non-Regulated Class B and C Noxious Weeds and Weeds of Concern widespread noxious and invasive weeds in King County, control not required but definitely a good idea whenever possible! Examples: English ivy, holly, butterfly bush, Scotch broom, etc.

11 Most Abundant Regulated Noxious Weeds in King County Giant Hogweed Garlic Mustard Tansy Ragwort Purple Loosestrife Spotted Knapweed Orange Hawkweed Policeman s Helmet Garden Loosestrife Sulfur Cinquefoil Dalmatian Toadflax

12 Examples of Non-Regulated Weeds Butterfly Bush Yellow Archangel Canada Thistle English Holly Blackberry English Ivy Bittersweet Nightshade Yellow Flag Iris Scotch Broom Knotweed Poison-hemlock Bull Thistle

13 Some Local Invaders and How to Control Them

14 Himalayan Blackberry (Rubus armeniacus) Evergreen Blackberry (Rubus laciniatus)

15 Blackberry Control Base control plan on ability to maintain Least infested areas first, then more heavily infested areas Preserve native vegetation Clear mature blackberry with loppers, brush mowers, machetes, or goats before seed set Dig up root crowns or spot spray resprouting canes at about 2 ft tall in late summer or fall (foliar spray or wiped onto fresh cut stems) Or cut several times a year for several years to exhaust the roots Mulch and re-vegetate as needed to reduce soil erosion and weed seedlings

16 Chemical Control of Blackberry Triclopyr amine (2-3% solution) apply anytime during active growth period spring to fall e.g. Garlon 3A, Brush B Gon, Lilly/Miller Blackberry and Brush Killer Or triclopyr ester (4% solution) is effective in the winter, when many native plants are dormant (leave 60 foot buffer from water) e.g. Garlon 4, Crossbow Or glyphosate (2-3%) fall application e.g. Roundup, Aquamaster Cut stem apply any of above per label to fresh cut stems, need to apply to both sides if rooted at nodes

17 English Holly (Ilex aquifolium)

18 English Holly Control Prevent further spread by removing berries or berryproducing trees Re-sprouts from cut stumps and root crowns so digging is best non-chemical method Cut stump or girdling with herbicide (glyphosate or triclopyr) is more effective than foliar spray

19 Scotch Broom (Cytisus scoparius)

20 Scotch Broom Control Plants under 3 feet can be hand pulled when soil is moist Remove larger plants with weed wrenches Can cut older plants near ground level in the dry season (July- September) Spray plants spring to early summer (before leaves fall) For less dense sites, use selective treatment cut stump (late spring), stem injection, basal/stem spray (in fall) Monitor site for at least ten years for new seedlings Broom removal with weed wrenches

21 English Ivy (Hedera helix, H. hibernica)

22 Ivy Control: Lifesaver Method Kill upper growth by cutting the vines all around the tree at about shoulder height and clearing the trunk. Pull up ivy about 6 ft from base of tree and maintain ivy-free area. Use a hand saw or clippers to cut vines and then pull vines off trunk

23 Ivy Control: Hand Pulling/Digging Hand-pulling ivy is hard work but very effective and gets done quickly with large groups of young volunteers! Pulled ivy can be rolled up like a carpet easiest to do from the top of the hill down!

24 English Ivy Control with Chemicals Waxy coating on leaves reduces herbicide uptake, especially during the summer and fall growing season Young ivy leaves absorb more herbicide than older leaves In the early spring or regrowth from being mowed Applying pelargonic acid before or with herbicide may increase absorption Or can create wounds with a weed trimmer before spraying Either glyphosate or triclopyr (2-5% solution) sprayed on a sunny winter or early spring day is more effective than summer or fall Can also cut stems and apply 25% solution glyphosate to freshly cut surfaces Ivy may respond slowly to herbicide, so wait to follow up for at least a few months Can combine methods: pulling where roots are accessible and chemical control for rocky areas or steep slopes

25 Old Man s Beard (Clematis vitalba)

26 Old Man s Beard Control Combination of cutting and chemical treatment Cut climbing vines in the winter at waist height (leave the top stems to wither) Spray the foliage in the spring to summer with triclopyr or glyphosate, avoid natives Mature plants use cut stump method Stem and root fragments should be collected and burned or disposed of; do not compost

27 Bittersweet Nightshade (Solanum dulcamara) This aggressive woody vine can form dense patches and blanket trees and shrubs along creeks

28 Bittersweet Nightshade Control Manual removal of roots can be effective Hand pull the stem close to the ground and pull or dig up the roots, taking care not to break the slender roots This method is most effective with young plants and new infestations Be thorough because stem and root fragments can re-sprout Along streams, need to prevent erosion, contain sediment Cutting may improve access to roots but won t control plants Chemical treatment: use care to avoid drift, spot spray or wipe on herbicides

29 Invasive Knotweed (Polygonum spp.)

30 Knotweed has hollow, upright, bamboo like stems, often reddish

31 Knotweed Control Non-Chemical Dig up individual plants growing in soft soil Dispose of roots and rhizomes in the garbage Cut down twice a month between April and August, once a month after that until the first frost Don t let stems exceed 6 inches Cut stems can be dried, crushed and composted Cover with heavy-duty erosion control fabric or sturdy plastic Weigh down with rocks or cement blocks (no stakes) Monitor and maintain (stomp down regrowth, pull or spray re-sprouts along edges, fix holes) Leave in place for five years Seattle Public Utilities Loose fabric allows growth without breaking through; rocks hold it down without creating holes.

32 Chemical Control Spraying or Injecting Spray the leaves and stems Imazapyr (most effective) or glyphosate (next best) Usually mid-june to September Continue to monitor sites for at least three years after knotweed appears to be gone Stem injection with concentrated glyphosate Need to inject every stem July to September Highly effective and reduces drift Some limitations Labor-intensive and uses more herbicide Limited to about 2500 canes per acre per year per glyphosate label Some stems will be too small to inject Will need to spray re-growth the next year Spraying knotweed re-growth Injecting knotweed

33 Yellow Archangel Lamiastrum galeobdolon (a.k.a. Lamium) Small yellow mint-type flowers in leaf axils Silvery markings on leaves of this popular garden plant make it easy to spot invading into shady forests

34 Yellow Archangel Infestation

35 Yellow Archangel Control Persistence Required! Hand pulling collect all roots and stems or they will regrow Covering needs to be very well-covered, no holes and extending beyond plants Spraying combinations and repeat treatment Glyphosate (Roundup) mixed with either triclopyr (Garlon), imazapyr (Habitat) or aminopyralid (Milestone) Add surfactant for best results Concentrated vinegar products short term control is good, need to re-apply regularly Regrowth after spraying Seedlings emerging in treated area

36 Herb Robert (a.k.a. Stinky Bob) (Geranium robertianum) Weak roots make this plant easy to pull but plants seed prolifically and germinates multiple times in a season so repeat visits to the same location are needed for complete control.

37 Some Threatening Noxious Weeds Prevention of spread in the county and state is highest priority Call your County Noxious Weed Program if you find these or any other regulated noxious weeds King County Pierce County Snohomish County

38 Garlic Mustard (Alliaria petiolata) Class A Noxious Weed Infestation along Longfellow Creek

39 Class A Noxious Weed Garlic Mustard (Alliaria petiolata)

40 Class A Noxious Weed Garlic Mustard In undisturbed forests, garlic mustard spreads up to 120 feet in one year. It inhibits tree growth through negative impacts on beneficial fungi and has no natural enemies in North America. Garlic mustard covering a hillside near Carkeek Park in Seattle.

41 Garlic Mustard in King County in

42 Garlic Mustard in King County 2011

43 Lots of Look-A-Likes Garlic Mustard Nipplewort (Lapsana communis) Nettles White-Flowered Money Plant

44 Don t take it with you Prevention of Spread Clean your boots and equipment Don t move mulch from infested sites

45 Giant Hogweed (Heracleum mantegazzianum) Class A Noxious Weed 15 feet tall with a stout, purple-blotched stem, large white umbrella-shaped flower clusters, and giant, sharply toothed leaves ashtabula.osu.edu

46 Giant Hogweed Use Caution When Handling Class A Noxious Weed Wear gloves and long sleeves when cutting off flower heads, then dig up roots Sap from hogweed causes painful burns

47 Giant Hogweed (Heracleum mantegazzianum)

48 Purple Loosestrife (Lythrum salicaria) Garden Loosestrife (Lysimachia vulgaris) Class B Noxious Weeds

49 Class B Noxious Weed Policeman s Helmet (Impatiens glandulifera) Annual with fleshy, reddish stems, 3-10 ft tall, flowers resemble English policeman s helmet, vary in color from white to dark pink-purple

50 Class B Noxious Weed Policeman s Helmet (Impatiens glandulifera) Policeman s helmet spreads along creeks and out-competes and crowds out other plants Can grow to 10 feet tall in one season Courtesy of Sasha Shaw, King County Noxious Weed Control Program

51 Managing Invasive Weeds in Urban Forests

52 FOOD FOR THOUGHT Some people say that invasive plants are just taking advantage of disturbed or poor conditions and aren t actually causing any problems. Is this true and should this impact how we do urban restoration?

53 Ecology-Based Weed Management Old approach see the weed, kill the weed New approach focus on prevention and establishing invasionresistant plant communities minimize disturbance like tillage, trampling use competition from established vegetation to help hold off weeds different strategies work at different stages of weed invasion Weed Population Growth Prevent Control Time Restore

54 First Step: Decide on Goals New and small infestations Prevention of spread is first priority Eradication is still feasible Established, large infestations Decide on level of control needed to reduce impact Remove entire plant for small infestations or high priority weeds like garlic mustard Consider regular cutting or covering to contain large infestations if resources are limited to allow natives to get established

55 Now, Consider Your Options

56 Manual Control Pull seedlings and young plants when small, before root systems fully develop Remove as much of the root as possible Limit disturbance and be sure to follow-up Digging giant hogweed Pulling gorse with a weed wrench Pulling and bagging garlic mustard

57 Mechanical Control Useful to reduce size, seed production and to starve roots Weeds will resprout after mowing and can be spread on equipment or by breaking up roots and rhizomes Best results when combined with manual control Himalayan Blackberry can be mowed to remove brambles Reduces seeding, but be careful not to move weeds on equipment

58 A Few Weeds Spread by Mowing Knotweed Garlic Mustard Tansy Ragwort Knapweed

59 Chemical Control Safety: Use with caution, protect skin and eyes Always follow the directions on the label Prevent drift (in water, other plants, etc.) Applications: Spot treatments, target the weed and avoid injury to desirable plants Incorporate other treatment methods Choose the least harmful herbicide that is appropriate for the weed and the site

60 Cultural Control Changes to environment to suppress weeds Shade/Cover Thick mulch Cardboard plus woodchips Weed fabric Competition Sterile grass Dense plantings of quick growing shrubs and trees

61 Finally, Follow up and Dispose Follow Up: Check site for several years Mulch to suppress weeds & improve soil Fill in holes with low-maintenance natives Disposal: Best: control before flowering! Noxious weeds: discard in garbage Widespread weeds: city yard waste or leave on site

62 Making the Best Use of Volunteers Large work parties Require oversight but can cover large areas quickly Best for dense patches of one or two target species (e.g. ivy and blackberry) in easy terrain Usually not as good at distinguishing weeds from natives Not so good for weeds requiring herbicide or careful weeding (e.g yellow archangel or knotweed) Dedicated forest stewards or friends of groups Better trained to detect and remove scattered infestations; don t waste them on large infestations Monitoring and mop up after large work parties Early detection and removal of new invaders (like garlic mustard) Marking invasive trees or weeds needing chemical control for removal by city crews

63 Making the Best Use of Staff Earthcorps, WCC, VCC, WA State Corrections, etc. Best for large, dense infestations and/or challenging terrain (steep slopes, dense blackberry) Better for targeting a limited number of species since ID skills can vary Clearing or grubbing out large areas and installing erosion fabric or plants Can do some herbicide applications if trained (e.g. knotweed injection, cut and wipe) City staff Coordination with stewards and work party supervisions Best for ongoing maintenance and mop up after large work crews Can be trained for early detection and control of a wide range of invasive species Most herbicide applications and power tools

64 Case Study: Happy Creek Park 1. Read the case study 2. Review the questions 3. Discuss as a group

65 The Problem: Happy Creek Park The Mayor has asked the Parks Department to restore Happy Creek Park, a 40 acre weed-infested natural area that has been left to itself since it was purchased for open space 50 years ago. The park has a pretty healthy stand of large Douglas firs and cedars and some native plants like sword fern and salal in the understory, mixed in with lots of herb Robert, English ivy, scattered English holly saplings, a few large English holly trees, and a few small patches of garlic mustard and yellow archangel. The maples and alders along the creek and several of the firs are covered with English ivy and Old Man s Beard. The streambanks are draped with dense vines of bittersweet nightshade. In addition, one side of the upper 500 feet of creek is bordered with invasive knotweed and lower down there are patches of policeman s helmet and purple loosestrife starting to spread from nearby private properties. And, of course, Himalayan blackberry is growing throughout the park wherever it can get enough sunlight. The Mayor wants the park to be weed-free in two years, but wants to keep the cost down by relying mostly on volunteers with small amounts of paid crew time.

66 Questions for Discussion 1. What control method and timing will work best on each weed species? 2. Where would you use volunteers or staff? Large work parties vs. forest stewards vs. park staff? 3. Which weeds are going to need repeat work in the same year? The following year? 4. Where are you likely to need to plant, mulch, control erosion? Where can you leave it to nature? 5. Are there any weeds you are unlikely to eradicate in 2 years? What should you tell the Mayor about what is realistic given the resources and timeline? 6. Do you think herbicides are needed to accomplish the goals of this project? If herbicides were not allowed, what, if anything, should change in terms of resources and/or expectations?

67 For More Info on Noxious Weeds in King County: Weed Photo Page: Search by Weed Name Click thumbnail picture to get more information and photos

68 Sasha Shaw King County Noxious Weed Program