Invasive Plant Control Options

Chemical treatment, biological treatment, photosynthesis interruption, aeration and systemic methods have all been tried as a means to control invasive plants.  Not all are effective.

 

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Clear Lake Solutions will help you select the most effective solution for your invasive plant problem.

Biological Control Methods: Milfoil Weevils, Sterile Carp

ProsCons
Uses “natural processes”Introduces non-native species
Banned in British Columbia
Slow impact on invasive plants
Has not proven to be very effective in practice

Biological control may sound like the most environmentally friendly solution to invasive plant control, but it is not.  While the Milfoil Weevil, an aquatic insect that feeds on the milfoil plant, and sterile grass carp, a fish that feeds on aquatic plants have been tried, neither of these species is naturally present in our lakes and ponds.  

Introducing non-native species can have very profound negative consequences on native plant and animal species and is therefore not allowed in many jurisdictions, including British Columbia.

VSHL Herbicides

ProsCons
Immediately effective on invasive plantsMay require regulatory approvals
Negligable impact on aquatic wildlifeLicensed applicators needed
Health Canada approved
Only impacts targeted plants
Often the lowest cost option

Very short half life (VSHL) herbicides offer an effective and environmentally friendly invasive plant control method.  Clear Lake Solutions offers Health Canada approved VSHL herbicides which only affect the unwanted plants to which they are applied and do not harm the other natural aquatic plants and animals.  The herbicides become fully non-toxic within 24 hrs and poses no long-term environmental consequences.  

Compared to other invasive plant control methods, VSHL herbicides are often the lowest cost option.  They are also the most effective method of controlling invasive plants and have the least negative environmental impact.  The most comprehensive study of invasive plant control methods “Lessons learned from invasive plant control experiments: a systematic review and meta-analysis” found that herbicides were “according to our meta-analysis, the most effective control method for reducing invasives“.

Effective against a broad spectrum of invasive plants, VSHL herbicides are easily applied by certified applicators supplied by Clear Lake Solutions.

Photosynthesis Interruption With Dyes

ProsCons
Quickly reduces submerged plant growthCan only be used in private ponds and lakes
Can provide longer term growth inhibitionImpacts all submerged plants, natural and invasive
Low cost for small pondsWill be depleted by rainfall and flow through streams
Imparts pleasing color to the waterCost prohibitive for larger water bodies
Does not affect other aquatic species or water fowl 

Dyes block sunlight from reaching the plants, thereby inhibiting their growth.  Dyes can be quite effective and provide a low cost option for smaller water bodies.  They also impart an attractive “blue” colour to the water.  However, since the dyes block the sunlight from reaching all submerged species, they are prohibited from use in natural water bodies.

dye

Photosynthesis Interruption With Liners and Barriers

ProsCons
Quickly reduces submerged plant growthCan only be used in private ponds and lakes
Provides long term growth inhibitionImpacts all aquatic plants, natural and invasive
Cost prohibitive for larger water bodies
Difficult to install

Liners and benthic barriers physically block sunlight from reaching the plants by covering bottom of the water body with a “mat”. This approach can be quite effective, but obviously is not selective and affects all plants, natural and invasive.   The cost of these barriers per square foot can be very high, so they are impractical in larger ponds and lakes.   Aquatic animals and water fowl will likely be negatively impacted by the lack of plant growth.

liners

Aeration

ProsCons
Promotes the growth of bacteria to consume excess nutrientsCan reduce but not eliminate invasive plant growth
No chemicals, dyes or barriers are usedRequires initial capital investment, ongoing operational cost and maintenance 
Slow impact on plant growth
Difficult to install

Aeration oxygenates the water which promotes the growth of aerobic bacteria and suppresses the growth of anaerobic bacteria.  The addition of aeration will increase the growth of aerobic bacteria which will consume both nitrogen and phosphorus from the water as long as there is also a source of carbon for the bacteria to feed on.  The reduction in nitrogen and phosphorus in the water slows the growth of the aquatic plants present.

As the bacteria grow they lower the level of nitrogen and phosphorus in the water by incorporating it into their cells.  However, this does not go on forever, because the bacterial growth tapers off as the bacteria population ages.  Surface area for aerobic bacterial growth is finite.  Unless bacterial cells are physically removed from the water system surfaces, a new equilibrium develops and the bacteria are no longer able to absorb more nitrogen or phosphorus.  Dying bacteria release their nitrogen and phosphorus back into the water.  So aeration can reduce both invasive and non-invasive plant growth in a body of water, but it will not eliminate growth.  Since the invasive plants are faster growing and hardier, they will out-compete the natural plants, leaving only the invasive plants to survive.

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Systemic Control Methods – Rototilling, Harvesting, Manual Exraction/Divers

ProsCons
Does not introduce anything “new” into the water bodySystemic methods encourage plant fragmentation and seed dispersal which increases invasive plant  growth in the long term
Immediate removal (short term) of invasive plantsCan have a significant negative impact on aquatic life 
Expensive

Systemic, mechanical extraction/harvesting, methods to control invasive aquatic plant species are a costly and short-term solution.  The main problem with these approaches is that the invasive plants that are being targeted spread through plant fragments and/or seeds from one water body to another.  All of the systemic approaches encourage plant fragment generation and seed dispersal, which just means that the invasive plant problem will return again, often in greater intensity than before.  

Systemic methods are expensive, involving divers and/or specialized equipment, plus the eventual disposal of the invasive plants removed.  The mechanical removal of the plants also disrupts the bottom of the water body, increasing turbidity and potentially choking out aquatic species.

Some of Clear Lake Solutions clients previously tried systemic methods and were disappointed with the results.  The solutions Clear Lake Solutions provided were much more effective and lower in cost.