Skip Treatments: When to use them and how to decide

Transcription

1 Skip Treatments: When to use them and how to decide Laurel Moulton Clallam County Noxious Weed Program

2 Introduction Started in 2004 with pilot study on Big River We have worked on ~23 rivers and streams Longer term project than initially thought Decreasing funding for all partners Knotweed infestations have decreasedbut rivers that need treatment have not Need decision making criteria to maximize efficacy without losing ground

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5 Adaptations tments later in season orter season nges in rates/method ostly switched to foliar, 1% Imazapyr ven t found magic bullet for small, epinasticre-growth urce limitations-labor, funding, treatment window EED TO DECIDE IF SKIP YEARS ARE A GOOD TOOL FOR BALANCING PROGRAM REACH AND EFFICACy-

6 Infestation trends: Hypotheses Lightly infested river = more gone or not showing up Giant knotweed least persistent of three If treated for 3-4 years, no great changes as a result of skipping No/few new sites Depending on disturbance factors

7 Clallam County treatment trends Generally treated for 3 years Generally treating later Generally reduced treatments for 1-3 years

8 What information do we have? Number of years treated before skipping. Number of years skipped How many new sites after skipping treatments? How many sites still gone after skip treatments? What does regrowth look like? Is it easier to find? STILL UNKNOWN: Will treatments after skipping be more effective because of greater surface area without losing ground to root growth or recovery?

9 2006 survey 2012 survey x Big River then and now Sites 593 incomplete 130 Description Dense stands Scattered stems/ clumps Scattered stems Biggest site Herbicide injected Herbicide sprayed Labor 1/3 sites 1000 s of stems stem* 65 gal 3.5 gal 0 4 sites >100 small stems gal 0.25 gal 3 month 5+ crew 12 days/ crew 6 days/ 2 crew

10 2007 survey 2012 survey x Clallam River then and now Sites 84 incomplete 77 Description Dense stands Scattered stems/ clumps Scattered stems Biggest site 28 sites = Herbicide injected Herbicide sprayed Labor Some sites still >100 stems* 33 gal 0.52 gal 0 1 site >100 lg stems 3 sites > 100 sm stems 2.14 gal 0.34 gal.25 gal Multicrews 8 days/ 2 crew 1.5 day/ 4 crew

11 2006 survey 2012 survey x Lake creek then and now Sites Description Biggest site Herbicide injected Herbicide sprayed Labor Dense stands 21 sites > 1000 stems Scattered stems NA 15gal 0 0 Scattered stems 1 site >50 stems 11gal gal gal 31 days/ 2 crew 11 days/ 2 crew 1 day/ 2crew

12 Observations Even now not every single spot has been surveyed nobody is perfect Need to do more complete surveying every few years Don t just go to known locations to check look further Look on wider flood plain areas away from river Advantage to newcomers fresh search technique, less project fatigue

13 Criteria for skipping river Species of Knotweed (Hoko) Bohemian vs. giant vs. Japanese Density of infestation (Big River) How dynamic is the river? (Lake Creek vs. Big) Flood events Size of flood plain Did you do a complete treatment (Clallam) Suggest doing 2-3 years of consistent, complete treatments before skipping a year (Lake Creek)

14 Risk Matrix Score 1 Score 2 Score 3 Giant knotweed Japanese Knotweed Bohemian Knotweed Low density, single plants Moderate density, sporadic clumps High density, multiple clumps-monocultures Low disturbance, confined Occasional disturbance, gradual banks High disturbance, followed by quiescence, off channel or bank terraces, log jams 3-4= Low Risk 5-6= Mod Risk 7-9= High Risk

15 Risk Matrix Score 1 Score 2 Score 3 Giant knotweed Japanese Knotweed Bohemian Knotweed Low density, single plants Moderate density, sporadic clumps High density, multiple clumps-monocultures Low disturbance, confined Occasional disturbance, gradual banks High disturbance, followed by quiescence, off channel or bank terraces, log jams 3-4= Low Risk 5-6= Mod Risk 7-9= High Risk

16 Risk Matrix Score 1 Score 2 Score 3 Giant knotweed Japanese Knotweed Bohemian Knotweed Low density, single plants Moderate density, sporadic clumps High density, multiple clumps-monocultures Low disturbance, confined Occasional disturbance, gradual banks High disturbance, followed by quiescence, broad flood plain, log jams 3-4= Low Risk 5-6= Mod Risk 7-9= High Risk

17 Take away messages Skip treatments are a reasonable tool - under the right conditions Increase collaboration/combine resources to hit a subset of rivers thoroughly each year Thorough treatment leads to better skip success At regular intervals repeat thorough survey Don t just go directly to known sites After change of management Encourage field observations, document changes Consider EDR&R or co-treatments of other priority?