Fighting Giant Hogweed

Transcription

1 Fighting Giant Hogweed A RETROSPECTIVE OF KING COUNTY S EFFORTS FROM 1996 TO 2014 Karen Peterson, Maria Winkler, Sasha Shaw King County Noxious Weed Control Program

2 Giant hogweed Heracleum mantegazzianum Is a very large, herbaceous plant in the Apiaceae or parsley family It comes from the western Caucasus Mountains (Russia, Georgia, Azerbaijan) It is considered noxious in several European countries It is listed as a Class A noxious weed here because of its invasiveness, and health hazards

3 Native range

4 How did it get here? Brought over as an ornamental Used as a tropical looking hardy plant in the gorilla exhibit at Woodland Park Zoo. Added bonus: the gorillas wouldn t eat it. (it s since been removed) Some homeowners in Seattle area took seed from hogweed in the Arboretum. Imported from the middle east as golpar, a spice used in cooking Used as forage until they realized it made the milk and meat taste bad.

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6 How to identify hogweed feet tall at maturity Red blotched stems, up to 6 in diameter

7 Giant Hogweed ID

8 Extremely large jagged leaves Raised, red blotches with hairs

9 Leaves from seedlings to adult

10 As they get older they get larger and more divided

11 Inflorescences can be up to 2.5 across Terminal flowers are those at the top on the main stem Most of those in the terminal are perfect, ie both male and female The umbels on lower and farther away umbels have perfect or just male flowers The higher order (farther from terminal) have more male flowers If there are both, the male flowers are located in the center

12 First signs of flowering begin in early May It usually takes an average of 44 days from blooming to seed set Flowers can be self fertile so there is a high rate of viable seeds per plant; 10-20,000

13 Good Guy Look Alike: Native Cow Parsnip dnr.wi.gov/invasives upload.wikimedia.org extension.unh.edu

14 Seedling in with buttercup and other plants

15 What makes hogweed such a problem? Each plant produces 10,000-20,000 viable seeds The seedlings germinate early Plants grow quickly early on, beating their competition to the sunlight with their large leaves It can regenerate quickly if cut back down to ground level, even when in seed set It doesn t have any specialized predators People are reluctant to control it because they are afraid of it Sap causes burns, blistering, blindness

16 But. It is monocarpic, it dies after it blooms The seed bank only lasts 3-5 years Most of the seeds germinate in the first year

17 What makes hogweed so scary? Most individuals experience burning, blistering, discoloration when coming in contact with the sap. Sometimes they show an increased sensitivity to sunlight for years Contact with the eyes can cause blindness, temporary or permanent

18 People are often exposed to sap when weed whacking or mowing Especially without adequate coverage Always wear long pants, long sleeves, gloves and eye protection when working around hogweed Hazmat suits not necessary

19 furanocoumarins These are the chemicals in hogweed evolved as a defense against predators Furanocoumarins are found mainly in the sap They are at their highest concentration in the seeds They are also found in other members of Apiaceae but hogweed has some of the highest amounts Furanocoumarins act as a phototoxin when exposed to UV light Photodermatitis can occur hours after contact with sap Wash immediately with cold water and cover to protect from light

20 Introduced to New York in 1917 Hogweed had been present in Seattle since the early 1950 s Within 40 years it had spread 7.5 miles along French Creek on Vancouver Island

21 Sites in King County since 1996 Dormant sites 1413 Closed sites 967 Total hogweed 1779 There were 116 sites found in 1996 There were 118 sites with hogweed on them in 2013

22 Known populations in King County 2000

23 Known populations in King County 2013

24 Sites surveyed in King County by year Sites Surveyed Sites with hogweed 200 0

25 New sites with hogweed 250 New sites New sites 50 0

26 Area found Area found

27 Hogweed controlled Sites surveyed Sites controlled 200 0

28 Where will it grow? In its native range, it grew in a wide variety of habitats with widely ranging temperatures Winter temperatures range from -33 F to 61 F Summer temperatures from 27 to 95 F Average annual rainfall is 34 (very much like ours) Will tolerate salt spray It is very adaptable

29 Once hogweed is established and there is no control, it will spread very quickly.

30 Giant Hogweed Control Use Caution

31 What doesn t work Even though it is monocarpic, cutting it back, even to the ground when seeds have formed, will still result in re-blooming and setting seed in the same season Cutting vegetative plants will result in regrowth Cutting immediately before or after spraying Spraying at too high a concentration or too low. Always check the label 2-4 d Stomping on them Leaving cut flower heads on ground. They will continue to flower and set seed

32 Giant Hogweed Control First, cut off and bag flower heads and leaves Next, dig up roots completely or cut root at 6 below stem Or, you can spray the plants with herbicide, either glyphosate or triclopyr The key is to control the roots don t be fooled by small upper growth

33 Timing Spray in spring while still actively growing Digging is easier when soil is still moist and blackberries are low enough to see the younger plants

34 Mechanical control Digging out the entire root Best for young plants Cutting root Be sure to cut at least 6 below stem Sometimes soil can pile around plant, so be sure to locate the top of the root

35 Chemical control Best products for control are those with Glyphosate or Triclopyr as an active ingredient Best control in spring while plant is still growing Denmark outlawed the use of pesticides on public property, but an exception was made for hogweed

36 Stem Injection Injection is also very effective for treating hogweed (Glyphosate - Roundup Pro or Aquamaster): Inject one leaf stem per plant 12 above root crown with 5 ml of a 5% solution of Roundup Pro Concentrate Flowering plants: inject main flowering stem near base, 2-4 ml of 100% glyphosate; use cavity needle (wall of stem too thick for regular needle)

37 Hogweed site in Normandy Park Before treatment

38 Biocontrol No insect, fungus or disease has been found that is specific enough to target hogweed alone. Except grazers like sheep, cows or goats (if not used for milk or cheese) Horses tend to avoid eating hogweed If using animals to graze, the best are those with dark skin and a dense coat. Otherwise they can be sensitive to the sap. They need to graze several times a year for several years (5-10) to achieve control

39 Control and Prevention Be aggressive Monitor Recheck sites for several years Educate the public

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41 Return of the Giant Hogweed Genesis, 1971 Turn and run! Nothing can stop them, Around every river and canal their power is growing. Stamp them out! We must destroy them, They infiltrate each city with their thick dark warning odour. They are invincible, They seem immune to all our herbicidal battering. Long ago in the Russian hills, A Victorian explorer found the regal Hogweed by a marsh, He captured it and brought it home. Botanical creature stirs, seeking revenge. Royal beast did not forget. He came home to London, And made a present of the Hogweed to the Royal Gardens at Kew. Waste no time! They are approaching. Hurry now, we must protect ourselves and find some shelter Strike by night! They are defenceless. They all need the sun to photosensitize their venom. Still they're invincible, Still they're immune to all our herbicidal battering. Fashionable country gentlemen had some cultivated wild gardens, In which they innocently planted the Giant Hogweed throughout the land. Botanical creature stirs, seeking revenge. Royal beast did not forget. Soon they escaped, spreading their seed, Preparing for an onslaught, threatening the human race. Mighty Hogweed is avenged. Human bodies soon will know our anger. Kill them with your Hogweed hairs HERACLEUM MANTEGAZZIANI Giant Hogweed lives

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43 King County Noxious Weed Control Program WEED