Managing Milfoil: Control Options for Eurasian Water Milfoil

1. 14 Sept 2019, NJCOLAPart 1 – Managing MilfoilPart 2 – What the HABs is Going On? Stephen J. Souza, Ph.D. Clean Waters Consulting, LLC SJSouza.CWC@gmail.com

2. Thanks To

3. Part 1 Managing Milfoil

4. Eurasian Water Milfoil

5. Life History Eurasian Watermilfoil • Submerged and weakly rooted, perennial plant. • Grows in variety of conditions – depth, clarity, pH, salinity • Prefers disturbed areas, with fine sediments, and ample nutrients • Spreads by seeds and fragments...vegetative growth primary reproductive strategy. • Autofragmentation or fragmentation by wind, waves, etc. scatters fragments that set root resulting in a new plant. • Autofragmentation and flowering/seed peak in July. • Plants die back in fall, but roots remain alive...enable plant to start growing quickly in spring.

7. Milfoil vs. Coontail vs. Parrot Feather

8. Before You Begin Sample Map milfoil density and distribution

9. Control Options • Physical • Biological • Mechanical • Chemical

10. The IPM Approach • Integrated Pest Management • Know your pests, know life history the target species • Define management objectives • Be proactive – not reactive • Combine techniques...don’t put all “eggs in one basket” • Understand pros/cons, etc. of control techniques • When using herbicides understand selected product, mode of action, dose rate and application technique

11. Physical Controls

12. Weed Roller • Powered device used to slowly and continuously disrupt soft sediment • Agitation limits establishment of weeds • Applicable only for small areas; dock or pier

13. Schematic of Unit in Operation

14. Weed Roller Controlled Weed Growth Plants Vs. No Plants Note furrows in sand caused by fins on roller

15. Benthic Mats • Used like black plastic in the flower bed. • Screen sediments from sunlight hampering weed and mat algae growth. • Need to use special material (negatively buoyant, durable and capable of venting trapped gas). • Cost approx $.70/ft2 for material only, $1.50/ft2 installed.

16. Benthic Mat – Basic Material

17. Benthic Mat - Preparation

18. Benthic Mats https://lakebottomblanket.com/

19. Lake Lowering • Lower lake in fall • Expose sediments to air • Allow sediments to freeze • Kill off milfoil fragments, roots and seeds

20. Lake Lowering • Inexpensive • Unpredictable results • May increase spread of some other invasives ( e.g., curly leaf pond weed and water chestnut) • Requires NJDEP permit – • Extent of lower • Duration of lowering • Start of refill • Potential impact to fishery

21. Water Dyes • Only feasible for small lakes/ponds with very slow flushing rate • Relatively inexpensive • Proactive, most effective if added before onset of a bloom • Could potentially increase water temp, but very unlikely significant • Bench test as could cause “off” color due to dissolved solids or turbidity • Some require NJDEP permit

22. Biological Controls

23. Biological ControlsGrass Carp and Milfoil Weevils

24. Grass Carp • Not same fish as common carp • White amur, Ctenopharyngodon idella • Native to Amur River basin,China • Member of minnow family • May live 20 years, but usual life span is 5 to 7 years • May grow to as large as 20” and a weight of 5.5 pounds in 2 years

25. Grass Carp vs Common Carp Grass carp Common carp

26. NJDEP Permit Requirements • Certified triploid sterile fish. • Waterbody <10 acres in size. • Must have 40% weed cover . • Outlet barrier required. • Stocking guided by NJDEP. • Stock at least 8” fish in spring. • Stock conservatively…3-5/acre. • Monitor conditions.

27. Milfoil Weevil • Aquatic milfoil weevil (Euhrychiopsislecontei) feed exclusively on species of watermilfoil including Myriophyllum spicatum. • Native to U.S., but more common naturally in New England states than Mid-Atlantic • The southern limit is northern New Jersey • Larvae purchased from commercial “nurseries” http://aquaweed.com/pdf/progressive%20weevil.pdf

28. Milfoil Weevil • Milfoil control mostly via larvae • The larvae are stem miners, but adults feed on the leaves • The weevil larvae about the size of a pin head

29. Milfoil Weevil • As larvae bore through and feed on internal content of the stems, the plant is weakened and collapses • Weakened plant may be less able to over winter or to out-compete other aggressive plants

30. Stocking Milfoil Weevils • Optimal stocking density approximately 1-3 weevils per stem...about $1.00/weevil • Typically introduce roughly 500 – 700 /acre • Introduced literally one at a time, laborious and costly • May take full season to see results, need to be patient!

31. Milfoil Weevil – Down Side • Results may come slowly • Expensive • Larvae susceptible to climatic events (prolonged ice cover, exposed shoreline) • Larvae susceptible to fish predation • As milfoil densities decline so will densities of weevils…lake can become re-infested

32. Mechanical Controls

33. Harvesting • Cut and remove milfoil • Selectively reduce the density and coverage of nuisance or invasive plant species • Create boat access and navigation channels • Create fishing lanes • Improve circulation and water movement • Improve swimming and decrease plant density issues that affect safety

35. Hand Harvesting

36. Semi-Mechanical Harvesting

37. Small Harvesters Most small, “homeowner” machines cut but don’t harvest. Need to manually rake up cut plant material. Lack the ability to handle dense growth.

38. Truxor – Intermediate “Harvester” • Highly portable maneuverable. • Works in very shallow, confined areas. • Lightweight. • Relatively powerful. • Available with various attachments.

39. Truxor Cut, Rake, Collect.

40. Typical 8 ft Diesel Powered Harvester Pilot House Cut Weed Storage Area Cutting Bar Paddle Wheel Diesel Engine Compartment

41. “Business End” Of Harvester Conveyor Side Cutter Bars Lower Cutter Bar

42. Supplemental Transport Barge Barge docks on lake with harvester. Load conveyed from harvester to barge. Barge transports cut weeds to shore for offloading

43. Shore Conveyors

44. Off Loading and Disposal Fully automated, involves minimal manual labor. Filled trucks offload at disposal site which could be landfill, composting facility, or farm.

45. Dewatering of Harvested Weeds

46. Hydroraking • Mechanically remove milfoil by roots...longer term weed control. • Can be conducted selectively • Can operate in shallow water (< 2 ft, rake to 9 ft) and confined areas where harvesting is difficult • Slower, more expensive, “sloppier” than harvesting...NJDEP now requires permit.

47. Hydroraking – Harvesting Alternative Paddle Wheel Propelled Barge Deep Tine Rake on Articulating, Extendable Arm

48. Weeds Transferred to Harvester or Transport Barge Hydrorake Operation Extracted Weeds and Hydrosoil On Rake

49. Miscellaneous Options • Suction dredge • Diver assisted hand pulling • Hand pulling • OK for small areas • Questionable efficiency • Could require NJDEP permit • Diver assisted options expensive

50. Chemical Controls