KLSA’s Guide to the Watermilfoil Weevil
Eurasian water-milfoil weevil (Alwin, 2008)
Milfoil management techniques
The milfoil weevil
Life cycle of the weevil
Stocking lakes with the weevil
The weevil in the Kawarthas
Regulatory issues in the Kawarthas
Economics of stocking projects
Survey of public perceptions
This Guide is based on a study commissioned by the Kawartha Lakes (Ontario, Canada) Stewards Association, conducted by four Ecosystem Management Technology students at Sandford Fleming Collegefrom January to April 2011. Their assignment was to collect information on the use of the milfoil weevil to manage Eurasian watermilfoil, including:
A comprehensive review of available literature
A resident survey
A review of important legislative considerations
Also contributing to the Guide is Kyle Borrowman, M.Sc. student in Environmental and Life Sciences at Trent University, who is actively surveying the milfoil weevil’s presence in Ontario lakes.
KLSA has commissioned further research on the Eurasian milfoil weevil in 2011. Results will appear in the KLSA Annual Report to be published in print and on this website in April 2012.
A native aquatic weevil which lives exclusively on watermilfoil has been found in many of the Kawartha Lakes. It shows promise as a biological control mechanism for the invasive Eurasian watermilfoil. However natural weevil densities do no typically reach levels that cause significant declines of Eurasian watermilfoil. This leads to stocking or augmenting native weevil populations to levels that can cause significant declines. Currently, there is no legislation that allows the release of the milfoil weevil into the Kawartha Lakes, other than for research purposes. If release were permitted, stocking lakes with this weevil would be expensive, costing upwards of $10,000 per initial stocking. Because it appears to be so effective, however, collaborative efforts among applicable authorities and those groups who are affected may be merited. Further study is needed.
Eurasian watermilfoil (Myriophyllum spicatum, herein referred to as EWM) is an invasive aquatic plant that has become widespread throughout North America, including many lakes and water systems in Southern Ontario. Millions of dollars are spent every year on this continent on physical and chemical management techniques to control nuisance populations of milfoil.1 Many of these methods are expensive, provide only temporary results and may have negative impacts on the surrounding ecosystem.
In addition to physical and chemical management, biological control of EWM using the milfoil weevil (Euhrychiopsis lecontei) has been tried throughout the United States since the 1990s and has recently received growing interest in Ontario including stocking projects in Puslinch Lake, Scugog Lake, and Jack’s Lake among others. This insect is native to North America, feeds specifically on milfoil (plants within the Myriophyllum genus) and is commercially available as a biological control agent.2
GETTING TO KNOW EURASIAN WATERMILFOIL (Myriophyllum spicatum)
Eurasian watermilfoil (EWM) is a submersed aquatic plant native to Europe and Asia that has become widespread throughout North America since the 1960s. Within Ontario, nuisance populations of milfoil have been identified historically throughout the Kawartha Lakes region of the Trent-Severn Waterway and in the Rideau Lakes system. Currently, populations of Eurasian milfoil have been identified across the province, most notably in southern Ontario and the Greater Sudbury Area. Milfoil has also been identified in the Muskoka lakes, Haliburton lakes and in several waterways along the north channel of Lake Huron.4
Growth and Habitat
Reproduction of EWM is possible by seed, stolon production and stem fragmentation. Most reproduction occurs through fragmentation caused by disturbance, such as boat motors or cutting, or by autofragmentation, a response to nutrient availability. Fragmented stems float through the water column until they lose buoyancy and root in the receiving sediments. Stem fragmentation is responsible for new invasions and long-distance dispersal as fragments become attached to boats and boat trailers and are transported to new waterways.3
Growth occurs early in the growing season once water temperatures reach 10ºC. Upon reaching the surface, the milfoil stem branches profusely, blocking available sunlight to other submersed plants underneath the canopy. This growth habit often results in dense monocultures of Eurasian watermilfoil. 3 EWM typically grows in mesotrophic* to moderately eutrophic* lakes in depths of one to four metres, although it has been found in areas up to 10 metres in depth. Depth range is limited by wave action and competition in shallow water, and typically by water clarity in deeper waters. In general, low density sediments with approximately 20% organic matter are sufficient for milfoil. 3
* Mesotrophic lakes commonly have clear water, with beds of submerged aquatic plants and medium levels of nutrients.
A eutrophic body of water has excessive nutrients and is subject to algal blooms resulting in poor water quality. The bottom waters of such bodies are commonly deficient in oxygen. Eutrophic waters commonly lack fish species like trout which require cold, well-oxygenated waters.
Eurasian watermilfoil is a rooted, submersed, perennial herb with finely dissected leaves.3 These leaves are located along the stem at every node in whorls of four. Leaves become dense toward the upper portions of the plant and around the stem. Each dissected leaf generally consists of 12 or more paired divisions. Flowering consists of tiny pink flowers that develop on red spikes that stand above the water. Winter buds can also occur and are often red or green in colour.5 The stems of younger shoots are green in colour; as they grow they turn beige and resemble spaghetti in appearance.
Myriophyllum: Water milfoil
Each leaf resemble a feather with threadlike leaflets on either side of a central axis. Eurasian milfoil has 12 to 20 leaflets on each side of the central stem (upper drawing). Northern milfoil, which is native to the Kawarthas, has 11 or fewer on each side (lower drawing).
Drawing by Colleen Middleton and Jessica Middleton for KLSA.
Proper identification of EWM can be difficult. There are several similar milfoil species native to Ontario, as well as other aquatic plant species that bear a resemblance. To make matters worse, EWM apparently hybridizes with its closest native relative, northern watermilfoil (Myriophyllum sibiricum) making identification reliant on genetic analysis in some cases.6
Despite their similarities, it is possible to make somewhat accurate identification of EWM and northern milfoil in the field. The lack of winter buds on northern watermilfoil and the number of leaf segments per leaflet are the most distinguishable differences between the two. Typically, northern watermilfoil consists of leaflets with less than 12 paired divisions whereas EWM consists of more than 12 paired divisions. Five leaves of EWM become closely arranged towards the apical meristem* of the plant; this is not as noticeable in northern milfoil. In addition, when pulled out of the water, leaves of EWM typically collapse onto the stem where as northern milfoil is somewhat rigid and the leaves hold their form out of the water.
Since identification can be difficult, we encourage people to collect samples or take pictures of the plant in question (including close-up pictures of the leaves, stems and flowers if possible) for identification by scientific advisors who work with our association. Consider uploading your pictures to KLSA’s Facebook page.
*Meristem: undifferentiated plant cells, an area where growth can take place.
Negative Impacts of EWM Infestations
EWM can alter many aspects of an aquatic ecosystem. It can reduce oxygen exchange and deplete the level of available dissolved oxygen in the water needed for a healthy lake. It may increase water temperatures, sedimentation and the loading rates of nutrients. It can cause a decrease in biodiversity by taking over areas once populated by native plant species. Reduced drainage and increased flooding are also negative effects that may occur when populations are very high.3 The consequences of herbicide use for EWM control can also have adverse effects on natural ecosystems.1
Tangled biomass of Eurasian water milfoil (Borrowman, 2010)
Economic and Social
Property values may drop when an invasion of aquatic plants affects recreational activities and the health of the lake. Tourism and local economies suffer if fewer tourists visit beaches and lakes, where aquatic plants make swimming, boating, fishing and commercial navigation a frustrating experience. Herbicide use as a control agent may cause water to become unsafe for drinking, swimming or fishing. Milfoil may also block intakes for hydroelectric turbines, drinking water and irrigation.3
CURRENT MANAGEMENT TECHNIQUES
Mechanical harvesting entails removal by physical means such as cutting, mowing, dredging, or hand harvesting. Mechanical harvesters and cutters can remove plants at desired depths. Although mechanical harvesting is effective, it is labour intensive and may actually increase seasonal biomass and exacerbate the nuisance problem. This is because milfoil fragments will root and re-establish themselves if they are not properly collected and removed. Large mechanical harvesters and cutters are not species specific and may remove beneficial native plants along with the milfoil.3
Chemical methods such as herbicides are usually effective but a last resort due to the harmful effects on the environment. Herbicides used for aquatic plant management are often broad spectrum and do not target specific plant species. The use of such herbicides could be detrimental to beneficial native plant and invertebrate communities. In some cases, such as treatment of Hydrilla spp., herbicide application has led to the production of resistant plant strains and the need for stronger herbicide dosage. Some herbicides that have been used to manage EWM include: 2, 4-diclorophenoxy, fluridone, triclopyr, diquat, and endothall dipotassium salt. Diquat is the only herbicide used inOntariowhile the others are heavily used in theUnited States.
Several native insects, and some naturalized ones as well (non-native and non-invasive) feed on and thereby suppress the growth of Eurasian watermilfoil. These include the milfoil weevil Euhrychiopsis lecontei, an aquatic moth Acentria nivea, the milfoil midge Cricotopus myriophylli, and to a lesser extent some caddisflies Tricoptera. Of these, the milfoil weevil is considered to be the most likely candidate for biological control of EWM.2
MEET THE MILFOIL WEEVIL
Weevils at work
The milfoil weevil is an aquatic beetle from the Curculionidae family and is native to North America. It is present in the Kawartha Lakes and is greatly distributed throughout southern Ontario and the northern United States. This herbivorous insect feeds solely on plants within the milfoil genus Myriophyllum species, and completes all life stages on its host. 2
The milfoil weevil is visible to the naked eye, although it takes a bit of training to spot one. The best way to observe the weevil is to snorkel through the milfoil patch focussing on the upper 30 centimetres of the milfoil plants. Weevils are about the size of a sesame seed, (two to three millimetres long, with a typical “weevil like” elongated nose (proboscus) and a yellow shell with black blotches or stripes. The underside (abdomen) is silvery in colour; in sunny conditions the silvery flash is what gives away their location. Weevils are very active as adults moving, feeding and mating as they travel along the stem or meristem of the plant. Not only are these critters small, they are also somewhat elusive, much like a squirrel around a tree. Milfoil weevils use the stem as cover to avoid predation and in some cases will play dead until they feel the threat has passed. This is often noticed when observing weevils in a sample tray.
Other signs of weevil presence are milfoil stem damage and the presence of eggs. These are easily viewed by collecting stems of milfoil (by snorkelling or by boat), then submersing them in water in a white tray. Stem damage consists of stem burrowing and pupae chambers. Burrowing is caused by feeding during the larval stage; the plant stem is hollowed out and sometimes breaks off. It is very noticeable when held up to light. Sometimes larvae can be spotted within the stem or along the outside of the plant. Pupae chambers form later in the life stage and further down the stem, typically 30 to 50 cm below the meristem. This will appear as a dark spot and bulge with a pupating weevil inside. If the adult has emerged from pupation, the dark spot will become a circular or elliptical hole about the size of an adult weevil.
The milfoil weevil is distributed across North Americain a range similar to the northern watermilfoil. Populations of the milfoil weevil have been identified within Quebec, Ontario, British Columbia, Albertaand Saskatchewanand in at least 44 states including Idaho, Colorado, Connecticut, Minnesota, Wisconsin, New York, and Washington.2,7,8,9
After ice-out each spring, the milfoil weevil moves from its winter hibernation site on shore, out into the milfoil patches. Once water temperatures reach 15OC, the female begins to lay eggs. It takes the milfoil weevil typically 17 to 30 days to complete its lifecycle, and multiple generations are possible per year. The weevil spends the summer months submersed and feeding on watermilfoil throughout all life stages, then adults leave the water in mid-September in search of natural shoreline sites for overwintering. They have a 60 percent rate of survival past winter, a mortality rate which is not severe. The weevil has four life stages: egg, larvae, pupa and adult as described below.2
Egg: 3 to 6 days
Weevil eggs are typically laid on the plant meristem and upper layers. They are yellowish, elliptical and about 0.5mm long. Eggs are difficult to see and are sometimes confused with blobs of algae, which have a fuzzy appearance compared to the solid colour of the weevil eggs.
Larva: 8 to 15 days
Larva phase (Newman ,2008)
Once the eggs have hatched, the larvae feed on the upper portions of the host and are usually three to five millimetres in length. Larvae spend the first three to five days of this stage feeding on the meristems*, eventually burrowing into the stem (also known as stem mining). Larvae cause the most damage to milfoil at this stage and on average consume 15 centimetres of stem. Then they begin to hollow out a pupal chamber, ready for the next stage of life.2
Pupa: 9 to 12 days
Pupa phase (Newman, 2008)
Pupation takes place 60 to 90 centimetres down the stem of the plant. Researchers believe this happens further down the shoot because the weevil prefers thicker stems for pupation. Studies indicate that at this stage weevils need minimal temperatures of 10˚C to successfully morph into adults.2
Adult weevil on watermilfoil stem (Johnson, 2006)
The adult weevil can grow to be two or three millimetres long at this final phase. They have been recorded living up to 162 days in laboratory studies.¹⁹ Females lay their eggs upon the apical (top) meristem of their host and can produce two to four eggs daily with a maximum of five generations per summer. Adults primarily feed upon the milfoil’s leaves but also eat stem tissues. Seasonally, the last generation of adults refrain from reproducing; instead, they store energy for development of wings and fat stores. This prepares them for the overwintering process, which has been observed occurring in leaf litter and other organic matter near the shoreline.
Making it through the winter
Weevils typically overwinter on shore in the top five centimetres or so of leaf litter, dry duff and soil. A study by weevil expert Raymond Newman in Wisconsin found highest overwinter weevil densities one metre from shore; at some sites it was not uncommon to find weevils overwintering on land up to six metres from shore. This is reassuring for weevil survival in the Kawarthas, where water levels change dramatically in November and April.
If they are still on land, weevils have been reported to head for the water shortly after the ice goes out, and have been collected on plants at this time. It is when water temperatures reach 10 to 15ºC that weevils begin to actively feed and reproduce. It takes about a week at 15ºC for a female to lay eggs. Other literature confirms that weevils should be in the water by mid-May. This seems to be a safe time for shore dwellers to rake up accumulated debris, without fear of removing precious weevils.
Choosing a host plant: native, Eurasian or hybrid?
The weevil is a selective diner. It lives only on watermilfoil plants, and does not spread to others. It is endemic to North America, which indicates that its original host plant choice was the northern watermilfoil. The spread of invasive EWM across North American regions has allowed EWM exposure to the milfoil weevil.
Laboratory studies have revealed that weevil growth and development occurs over a shorter period of time on EWM in comparison to northern milfoil, and EWM is preferred over its native counterpart for egg laying.2, 10 Further studies have found hybrids of Eurasian and northern watermilfoil occurring throughout Ontario and the midwest United States. This includes several of the Kawartha Lakes (Lower Buckhorn, Pigeon, Scugog and Stony) as well as theRideauLakes system. In laboratory studies milfoil weevil performance on hybrid milfoil is intermediate in comparison with EWM and northern milfoil.
One might wonder, then, if hybrids could be more invasive (through hybrid vigour and fragmentation) and be less susceptible to the milfoil weevil because of a natural resistance inherited from northern watermilfoil. Although this is possible, early surveys of hybrid milfoil populations throughout Ontario have determined that the milfoil weevil does naturally occur on these hybrids in similar densities to those on EWM. There is a need for more research in order to fully understand the relationship between weevils and hybrid watermilfoil.10
Impact of the weevil on EWM
The greatest threat to milfoil survival occurs when the weevil larvae burrow into the stem and consume cortical and vascular tissue. This mining action interrupts the flow of nutrients through the plant. Stem mining also forms holes in the shoot’s walls, releasing gases that keep the plant upright. Reduced buoyancy makes the plant sink out of the water column inhibiting root production and eventually leading to the collapse of entire EWM beds2. Weevils survive and reproduce abundantly on EWM, and populations can reach levels capable of controlling EWM biomasses. Conversely, on native milfoil plants, weevil populations are said to remain low, and they generally do not negatively affect the native milfoil population. However, weevil densities in most lakes are not adequate to control the invasive EWM without stocking methods.2
Darker areas of the milfoil stem depicting weevil damage (Ross, 2010)
Currently, there is no legislation that allows the release of the milfoil weevil in theKawartha Lakes, other than for research purposes.
Canadian Food Inspection Agency (CFIA)
Under the National Animal Health Program, the CFIA establishes import requirements for all animals and animal products that enterCanada. An import permit is required to bring milfoil weevils across the border intoCanada. If anOntariosource of weevils is found, then the import permit is not required. Permit applications are available at:
Ontario Ministry of Natural Resources (OMNR)
Under the Fish and Wildlife Conservation Act section 54 (1) (Release of Imports), “except with the authorization of the Minister, a person shall not release wildlife or an invertebrate that has been transported intoOntarioor has been propagated from stock that was transported intoOntario.” However, this Act does not apply if an import permit is issued by the Canadian Food Inspection Agency.
Curve Lake First Nation
TheKawartha Lakesare situated within the traditional territory of Curve Lake First Nation. The First Nation territory is incorporated within the Williams Treaty Territoryand is the subject of a claim underCanada’s Specific Claims Policy. Consultation with Curve Lake First Nation’s Rights and Resources committee is a very important step and also an obligatory duty outlined by the Supreme Court of Canada. To set up a meeting, contact their cultural outreach coordinator at:
ECONOMICS OF TYPICAL WEEVIL CONTROL PROJECTS
Budgeting can be the one factor that contributes to the success or failure of EWM biological control methods. As discussed below, the cost can be prohibitive. However investment in biological methods for control of the EWM plant and for spread prevention are reasonable considerations for communities troubled by this nuisance species.
What Eurasian watermilfoil costs
Millions of dollars are spent annually on control of EWM in the United Statesincluding mechanical, physical and biological management techniques and invasion prevention programs. In addition to control costs, EWM may contribute to billions of dollars in lost revenue from recreational activities such as swimming, boating and fishing, which are hindered during peak seasons in lakes across the United Statesand Canada.14
What weevils cost
Nancy Cushing of the U.S.company EnviroScience Inc. estimates a cost of $1.00 to $1.20 per weevil, with a minimum of 10,000 to 50,000 milfoil weevils needed to start introductory EWM plant control.15 A single EWM biological control project can cost up to $95,000 but this estimate is not typical; it allows for unexpected circumstances during the project start up. Madsen et al. (2000) stated that weevils were sold in units of 1000 individuals. Generally, 3000 weevils per acre were needed for efficient control.14 The cost for lake surveying, weevil application and post application monitoring can range from $1,000 to $3,000 per step for a typical lake project. Other control methods such as herbicides can cost up to $110,000 and harvesting may be even more expensive.15In perspective, using the milfoil weevil to control EWM is not only a more cost effective method but it is also sustainable in the long term, with ecological benefits.15
PUBLIC PERCEPTION OF BIOLOGICAL CONTROL METHODS
Public perception of invasive species and biological control methods plays a large role in the practice of biological control. There are five ‘publics’ involved in any biological control project:16
Open communication with all five parties is essential at all times in any project. The science of biological control is a public-interest science, which means that practitioners need to understand the public and cultivate public support for their work.16 The public’s perception of the potential risks and benefits associated with biological control methods plays a key role in the success or failure of a project.
How people perceive risk is key. In biological control, risk is measured by quantifying potential damage to the public, such as the sport fishing industry, or to beneficial native plant species such as wild rice, through a risk assessment process.
Ethics is not often discussed in the context of biological control programs, despite the fact that ethical and emotional decisions must be made when considering the release of any biological control agent. For control programs to be ethical, all reasonable alternatives must be listed and people choose objectively among them to compare the consequences of actions.17 This helps to inform and reassure everyone involved. There are a number of things that biological control scientists can do to quantify, predict and minimize risks. Proper risk assessment is vital to the success of any proposed project.
Results of an online survey on biological control
One way to assess public interest in biological control methods is through a survey. Surveys give the public an opportunity to voice their support, ask questions and share concerns about invasive species and control methods. The Kawartha Lakes Stewards Association invited 350 members to take a survey on invasive species control during a two week period spanning February and March of 2011, hosted on SurveyMonkey.com. 90 of the 350 people completed the survey, a response rate of 25.7%. This rate is very high, and indicative of the interest level amongst KLSA members.
Of those who completed the survey, 77% have noticed an increase in the presence and/or density of Eurasian watermilfoil or other aquatic plants in recent years (Figure 8). 69% polled are able to identify Eurasian watermilfoil, but only 47% are aware that a native aquatic insect, the milfoil weevil, can be used to reduce the abundance and density of Eurasian watermilfoil in lakes. It is interesting to note that 100% of participants consider the problem of invasive, exotic plants to be important or very important. These results indicate that people are concerned about invasive aquatic plants.
Use of the milfoil weevil to control Eurasian watermilfoil in theKawartha Lakescomes with a number of ecological, economic, regulatory and social considerations. All four of these spheres must be considered from the outset of any project, and all stakeholders should be included in the discussion from the very beginning. Based on our research into the ecology, feasibility, and regulatory considerations of using the weevil to control Eurasian watermilfoil in the Kawartha Lakes, here are recommendations for any group wishing to pursue this form of biological control.
Map the location and density of Eurasian watermilfoil in this area. This will help to determine where the problem areas are, and where research should be focused.
Disseminate information on biological control of Eurasian watermilfoil by the milfoil weevil toKawartha Lakesresidents. This will better inform the public of the problem of invasive species, and the potential of biological control methods.
Hold an information session to discuss the project with potential stakeholders and residents who may be affected by a biological control project. Deal with concerns and considerations that come to light, before the implementation stage.
Encourage invasive species scientists to produce more research on weevil control programs, the establishment of baselines for monitoring, and long-term effects.
Encourage legislation that allows the release of the milfoil weevil in the Kawartha Lakes, other than for research purposes. This will require collaboration to produce a studied and persuasive case for further biological control projects.
Contact other lake associations throughout the United States and Canada to inquire about their weevil stocking experience.
Set up a monitoring program to collect information before and after to determine the success of the project. Excellent information is available through the Citizen Lake Monitoring Network in Wisconsin, USA, including a guide to weevil and milfoil monitoring. Visit http://www.uwsp.edu/cnr/uwexlakes/clmn/AIS-Manual/12weevil10.pdf
Establish a lead authority to pursue recommendations prompted by this report.
1. Richardson, R. J. (2008). Aquatic Plant Management and the Impact of Emerging Herbicide Resistance Issues. Weed Technology, 22, 8-15.
2. Newman, R. M. (2004). Biological Control of EWM by aquatic insects: basic insights from an applied problem. Stuttgart. 159-166.
3. Smith, C.S & J.W. Barko. (1990). Ecology of EWM. Journal of Aquatic Plant Management, 28, 55-64.
4. Borrowman, K. (2011). EWM: Life History, Habitat and Management. Trent University, unpublished data.
5. Crow, G.E. & C.B. Hellquist. (2000). Aquatic and wetland plants of Northeastern North America Vol. 1. The University of Wisconsin Press,Madison,Wisconsin
6. Moody, M.L. & D.H. Les. (2007). Geographic distribution and genotypic composition of invasive hybrid watermilfoil (Myriophyllum spicatum× Myriophyllum sibiricum) populations in North America. Biol. Invasions. 9(5): 559-570.
7. Creed, R. (1998). A Biogeographic Perspective on EWM Declines: Additional Evidence for the Role of Herbivorous Weevils in Promoting Declines? Journal of Aquatic Plant Management, 36, 16-22.
8. Newman, R. M. & W. G. Inglis. (2009). Distribution and Abundance of the Milfoil Weevil, Euhrychiopsis lecontei, in Lake Minnetonka and Relation to Milfoil Harvesting. Journal of Aquatic Management, 47-57.
9. Jester, L., Bozek, M., Helsel, D. & S. Sheldon. (2000). Euhrychiopsis lecontei Distribution, Abundance, and Experimental Augmentations for EWM Control in Wisconsin Lakes. Journal of Aquatic Plant Management, 38, 88-97.
10. Roley, S. & R. Newman. (2006). Developmental Performance of the Milfoil Weevil, Euhrychiopsis lecontei (Coleoptera: Curculionidae), on Northern Watermilfoil, EWM, and Hybrid (Northern X Eurasian) Watermilfoil. Environmental Entomology, 35(1), 121-126.
11. Mazzei, K. C., Newman, R. M., Loos, A., & D. W. Ragsdale. (1999). Developmental rates of the native milfoil weevil, Euhrychiopsis lecontei, and damage to EWM at constant temperatures. Journal of Biological Control, 16, 139-143.
12. Newman, R. M., Ragsdale, D. W., Miles, A. & C. Oien (2001a). Overwinter habitat and the relationship of overwinter to in-lake densities of the milfoil weevil, Euhrychiopsis lecontei, a EWM biological control agent. Journal of the Aquatic Plant Management, 39(1), 63- 67.
13. Sheldon, S. & R. Creed. (2003). The effect of a native biological control agent for EWM on six North American watermilfoils. Aquatic Botany, 76, 259-265.
14. Madsen, J. D., H. A. Crosson, K. S. Hamel, M. A. Hilovsky, and C. H. Welling. 2000. Panel Discussion – Management of Eurasian watermilfoil in theUnited Statesusing native insects: State regulatory and management issues. Journal of Aquatic Plant Management 38: 121-124.
15. Cushing, N. (2011). EnviroScience Inc. Telephone Conversation. 14 February 2011.
16. Warner, K.D., J.N. McNeil & C. Getz. (2009). What every Biocontol researcher should know about the public. Proceedings from the XII International Symposium on Biological Control of Weeds. Accessed from http://webpages.scu.edu/ftp/kwarner/ageco-Warner-ISBCW-Public.pdf
17. Delfosse, E. S. (2005). Risk and ethics in biological control. Biological Control, 35, 319-329.
Rutgers University has extensively studied Curly Leaf Pondweed as well as the various means of control. We feel it would be helpful if we provided you with their study. It shows the effectiveness of grass carp, the issues with mechanical harvesting, and the difficulties of utilizing synthetic herbicides.
To review this study, please click below:
There are several members who apply natural/organic fertilizers to their lawns and gardens thinking the are helping save our lake. The truth is that all fertilizers end up feeding the weeds in the lake. Over 50% of the nutrients that flow into lakes are from lawns and gardens. We need to stop this flow.
There are a few at the lake who are investigating how fertilizers may be used with the least impact. Hopefully, this work will lead to clearer guidelines the Board will approve and distribute to members.
It is important that we use organic pesticides and herbicides in our yards to avoid harmful chemicals flowing into our lake. This article highlights some of the alternatives to chemicals.
Organic pesticides and herbicides
We have learned to think carefully about the chemicals we use to protect our property (and family!) from bugs and weeds. There is a growing concern about the personal and environmental effects of long-term low-dose exposure to many commercial pesticides and herbicides. One thing that isn’t changing is our desire to avoid these weedy and multi-legged pests as much as possible. Luckily, organic pesticides and herbicides are available on the market. You can also make your own from natural and effective ingredients. Remember to keep even natural products away from children and pets.
The EPA classifies twelve of the twenty-six most-used pesticides in the U.S. as carcinogenic. No wonder people are looking for alternatives! Here are some that are not toxic to humans:
Boric Acid. One of the most common ingredients in natural pesticide recipes and consumer products is boric acid, which will help eliminate carpenter ants, termites and cockroaches. For ants, mix together 1 liter of water and 1 teaspoon of boric acid. Soak cotton balls in the liquid and place them in a small container with holes in the lid (large enough for ants to get in). Place this in an area where ants are spotted.
You can use boric acid to kill off a termite colony. Make a bait trap with a piece of wood treated with boric acid. To treat a piece of unfinished wood, dissolve four tablespoons of boric acid in boiling water, pour in a spray bottle and spray on wood. Bury in the ground near your foundation where you have an infestation.
Boric acid can also help to control cockroaches. Since cockroaches like high spots, sprinkle a little powder in places such as the top of the refrigerator and cupboards.
Neem Oil. This oil is extracted from the neem tree of India. It contains a compound called sallanin. When sprayed on leaves, it protects plants from chewing insects like weevils.
Insecticide Soap. You can easily make your own spray by mixing two tablespoons of pure castile soap with one quart of water. Spray on plants to control aphids, leaf hoppers, whiteflies and mites.
Diatomaceous Earth. This is a dust made of marine organism shells that deters and kills creepy-crawlies such as ants, ticks, cockroaches, earwigs, slugs, and silverfish.
Look for organic pesticides with natural ingredients in home and garden stores. They feature a number of plant oils and other natural ingredients.
Organic Mosquito Repellents
Repelling insects is vital for comfort and health. A study by the New England Journal of Medicine reported that eucalyptus oil (30 percent concentrate with a 70 percent cineole content) will keep bites at bay for two hours, Bite Blocker (2 percent soybean oil) for an hour and a half, and citronella for 20 minutes. Neem oil is also used to repel mosquitoes. The good news is that these oils also repel other pests, such as gnats and ticks.
To repel mosquitos with plants, plant marigolds, mint, pennyroyal, rosemary or wormwood in your garden. Many stores now carry organic repellents.
Getting rid of weeds naturally can be as easy as picking them, root and all. Be sure not to mow or compost them, since doing so spreads the seeds around your yard.
Since the lawn is usually the main component of the yard – and the place where we play with our children and pets – using a natural weed controller makes sense. Instead of typical weed-and-feed products for the lawn, try corn gluten meal. It is a pre-emergent (a product that prevents growth) that controls dandelions, smart weed, crabgrass and more.
To spot-treat weeds, make a homemade vinegar spray. It works by altering a plant’s pH balance. Mix four ounces of lemon juice concentrate with one quart of vinegar and pour the mixture into a spray bottle. You can also pour boiling water on weeds to kill them. Cut off the top of the weed and slowly pour the hot water onto the crown.
Spring mulching is a great way to choke weeds in a flower beds. If you are planting an entire bed this year, incorporate a weed barrier.
Keeping your family and property pest-free doesn’t require harsh chemicals. Stores now carry plenty of natural products to control insects and weeds. Also, the Internet has thousands of sites that contain recipes for organic pesticides and herbicides.
You can prevent bugs naturally with hardscaping and xeriscaping. Learn how to get free mulch, too.
Author Anne Burkley is a writer from central Pennsylvania.
Organic Herbicides To Fight Weeds
An important thing we can do is not use pesticides and herbicides in our gardens as these flow into our lake. We strongly urge our neighbors to use natural or organic herbicides and pesticides.
From Organic Gardening:
Q: Although our brick patio has a plastic liner, weeds are starting to pop up in the cracks. The tight spacing between the bricks makes it difficult to remove the weeds by hand. Are there any safe organic herbicides to effectively control weeds coming up through our patio?
A: Most organic herbicides are nonselective, making them hard to wield against weeds in a lawn or garden, but useful where eradication is the goal. Ready-to-use products that zap weeds with fatty acids (herbicidal soap), vinegar (acetic acid), or essential oils (such as eugenol, or clove oil; and d-limonene, or citrus oil) are available from various manufacturers. You can find these at online gardening=supply retailers or at well-stocked garden or home centers. Most are at their weed-scorching best when applied to young weeds on a hot, sunny day.
Straight vinegar or vinegar with a squirt or two of dishwashing liquid will also lay weeds low, but it may take repeated applications to do the job. The more acidic the vinegar, the more effective it will be at controlling weeds, but it also becomes more dangerous for you to handle as the concentration increases. “Regular” grocery-store vinegar typically has 3 to 5 percent acidity; you may be able to find 10 percent vinegar at a restaurant-supply store or where supplies for pickling are sold. Repeated applications of vinegar will acidify the soil, making it harder for future generations of weeds to get a roothold.
Speaking of scorching, you could also invest in a handheld flame weeder – basically a propane torch with an extended nozzle – that lets you wipe out weeds without any herbicides at all. You can find flame-weeder nozzles that attach to a gas-grill-sized propane tank by means of a long hose, or small models that use a I-pound propane tank you can carry easily. An advantage of a flame weeder is that you can use it in the winter to rid you patio of treacherous icy patches, too.
Another popular organic method of dealing with weeds is boiling water. Organic growers sometimes use steam instead of flame to control weeds, and you could simply wander about your patio with a teakettle, scalding every pesky plant you see. Not every weed will succumb easily to this method – and depending on the size of you patio, this may be as tedious as hand weeding but with the added risk of splashing yourself with boiling water.
Visit organicgardening.com for more tips.
In the 1940s, Americans found a new way to love salt. Not simply for sprinkling on food — we’d acquired a taste for the mineral long before that — but for spreading on roads and sidewalks. Salt became a go-to method to de-ice frozen pavement.
During the past half-century, annual U.S. sales of road salt grew from 160,000 tons to about 20 million tons, as a group of environmental scientists pointed out in a study published Monday in the Proceedings of the Natural Academy of the Sciences. NaCl kept roads free from slippery ice, but it also changed the nature of North America’s freshwater lakes. Of 371 lakes reviewed in the new study, 44 percent showed signs of long-term salinization.
Extrapolating that finding for all of North America, at least 7,770 lakes are at risk of elevated salt levels — a likely underestimate, the researchers said.
Theirs is the first study of freshwater lakes on a continental scope. “No one has tried to understand the scale of this problem across the continent in the Northeast and Midwest, where people apply road salt,” said study co-author Hilary Dugan, a University of Wisconsin-Madison freshwater expert.
No federal body tracks how much salt gets spread on our roadways or makes its way into our lakes. So the researchers hoovered up a vast number of different data sets, produced by states, municipalities and universities. The study was the product of several “big, nasty, hairy heterogeneous databases,” as co-author Kathleen Weathers, an ecologist at the Cary Institute of Ecosystem Studies in New York, described it.
Each lake in the report had chloride measurements going back 10 years or more, was at least four hectares in size (about nine football fields or larger) and was in a state that regularly salted its roads during winter. The study authors also analyzed what percentage of the lake was surrounded by an impervious surface. This could be any combination of roadways, sidewalk pavement, boat launches or other hard surfaces.
Impervious surfaces, critically, allow dissolved salt to slide into lakes rather than soaking into soil. If at least 1 percent of the surface circling a lake was impervious, the lake was at risk of high chloride concentrations, the environmental scientists found.
Across all lakes, chloride concentrations ranged from 0.18 to 240 milligrams per liter, with a median of 6 milligrams per liter. (Seawater, by contrast, is much saltier — an average of about 35 grams per liter.) The Environmental Protection Agency recommends that salt in drinking water exceed no more than 250 milligrams per liter, at which point water tastes salty.
The scientists could not directly measure how much of the chloride came from road salt. But previous research indicated that agriculture, water softeners and other sources played only minimal roles. “Road salt is the major driver for chloride loading,” Dugan said.
Environmental scientists had previously observed rising salt levels in the nation’s rivers and streams. “These trends have been going on for decades,” said Sujay Kaushal, an ecologist at the University of Maryland who was not involved in the new study. Kaushal has assessed freshwater streams that have wintertime salt concentrations up to 40 percent that of seawater. Saltwater plants now grow in some of these streams.
Lakes are generally less susceptible than streams to changes like salinization. They may also serve as sources of drinking water.
James P. Gibbs, a conservation biologist at the State University of New York who was not affiliated with the new research, said that combining the lake data sets must have amounted to a “herculean effort.”
Gibbs has studied roadside pools and springs where amphibians lay their eggs and observed a “pretty high reduction in survival rates” of eggs and young in pools contaminated with road salt. Few amphibians live in large lakes, he noted. (“Lakes mean fish, and fish are bad news for amphibians.”) But he and other environmentalists are concerned that exotic species, better suited for brackish water or tolerating chloride, will move into saltier lakes.
If current trends continue through 2050, 14 of the lakes studied would exceed the EPA’s “aquatic life criterion concentration” of 230 milligrams per liter, the study authors predict. Another 47 would have a chloride concentration above 100 milligrams per liter.
“Right now it’s about ecosystems and biota,” Gibbs said, meaning animal and plant life. “It is kind of alarming. Ultimately, we’re looking at a human health issue.”
The average water treatment system will not remove dissolved elements like chloride ions from water. “You can’t filter out these salts,” Kaushal said.
Increased salt in drinking water poses health problems to humans who have kidney trouble, use dialysis or have hypertension. Kaushal has personal concerns about the matter, too — for his young child’s health. He lives in an area where high salt levels were likely responsible for turning Montgomery County’s drinking water brown in 2015, when, the theory goes, road salt stripped manganese from old pipes.
“I think it should be listed as a primary contaminant,” just like potential pollutants such as nitrogen and phosphorous, he said. Changing our salty ways, though, may not be simple. “About 10 years ago, I was asked by a state senator in Maryland to testify on a road salt bill,” he said. “And when he presented that, all of the other senators laughed at him.”
Some municipalities have improved how they manage salt by tweaking the rate at which trucks dump salt on roads, for example. But signs point to an increased reliance on salt. In winter 2014, the Wall Street Journal reported that road salt prices surged by 20 percent due to a huge demand.
“We also are experiencing changes in the frequency and intensity of ice storms and snowstorms,” Weathers said. “It’s clearly a case where science can and should be used to help guide management decisions.”
Even if we curb our enthusiasm for road salt, it will take some time for the environment to respond. In the latter half of the 20th century, Germany decreased the amount of road salt it used. But the country’s lakes only recently began to show lower salinity levels. “There’s a lag after stopping laying down salt — a lot of salt is stored in soils,” Dugan said. “It’s like a reservoir of salt.”
Individual business and property owners are responsible, in some cases, for up to half of all road salt used, Dugan said.
For those caught between the need to keep their pavement safe and a desire to be environmentally conscious, Kaushal advised a more judicious approach. “People tend to think more is better, so they just dump or cake it on,” he said. He recommends salting before a snow event. “That’s going to be more effective.”
And some states are exploring different de-icers — like beet juice or, in Wisconsin, liquid cheese brine. At low temperatures, the latter is more efficient than just salt.
First evidence found of popular farm pesticides in drinking water
By Ben Guarino April 5
Of the many pesticides that American farmers have embraced in their war on bugs, neonicotinoids are among the most popular. One of them, called imidacloprid, is among the world’s best-selling insecticides, boasting sales of over $1 billion a year. But with their widespread use comes a notorious reputation — that neonics, as they are nicknamed, are a bee killer. A 2016 study suggested a link between neonicotinoid use and local pollinator extinctions, though other agricultural researchers contested the pesticides’ bad rap.
As the bee debate raged, scientists studying the country’s waterways started to detect neonicotinoid pollutants. In 2015, the U.S. Geological Survey collected water samples from streams throughout the United States and discovered neonicotinoids in more than half of the samples.
And on Wednesday, a team of chemists and engineers at the USGS and University of Iowa reported that they found neonicotinoids in treated drinking water. It marks the first time that anyone has identified this class of pesticide in tap water, the researchers write in Environmental Science & Technology Letters.
Gregory LeFevre, a study author and U of Iowa environmental engineer, told The Washington Post that the find was important but not immediate cause for alarm.
“Having these types of compounds present in water does have the potential to be concerning,” he said, “but we don’t really know, at this point, what these levels might be.”
If the dose makes the poison, the doses of insect neurotoxin reported in the new study were quite small. The scientists collected samples last year from taps in Iowa City as well as on the university campus and found neonicotinoid concentrations ranging from 0.24 to 57.3 nanograms per liter — that is, on a scale of parts per trillion. “Parts per trillion is a really, really small concentration,” LeFevre said, roughly equal to a single drop of water plopped into 20 Olympic-size swimming pools.
The Environmental Protection Agency has not defined safe levels of neonicotinoids in drinking water, in part because the chemicals are relative newcomers to the pesticide pantheon. “There is no EPA standard for drinking water,” LeFevre said.
The pesticides, most of which were released in the 1990s, were designed to be more environmentally friendly than other chemicals on the market. The compounds work their way into plant tissue rather than just coating the leaves and stems, requiring fewer sprays. And though the pesticides wreak havoc on insect nervous systems, neonicotinoids do not easily cross from a mammal’s bloodstream into a mammalian brain.
In 2015, environmental health scientists at George Washington University and the National Institutes of Health published a review of human health risks from neonic pesticide exposure. Acute exposure — to high concentrations over a brief period — resulted in “low rates of adverse health effects.” Reports of chronic, low-level exposure had “suggestive but methodologically weak findings,” with a Japanese study associating neonicotinoids with memory loss.
Melissa Perry, a public health researcher at George Washington University who was involved in that review, said via email that the new study “provides further evidence that neonicotinoid pesticides are present in our daily environments. From a public health standpoint, this issue clearly needs better attention.”
The Iowa scientists tracked neonicotinoid concentrations in the local drinking supply from May to July, the seven-week span after the region’s farmers planted maize and soy crops. Every sample contained three types of neonicotinoids: clothianidin, imidacloprid and thiamethoxam.
“Everything in the watershed is connected,” LeFevre said. “This is one of many types of trace pollutants that might be present in rivers.” (The USGS released an interactive map of the nation’s water quality on Tuesday, where those inclined can track trends in common pollutants.)
Most water filtration systems target clay, dirt or other particles, as well as pathogenic contaminants like bacteria. They’re not designed to eliminate chemical pesticides — and the properties of neonicotinoids make these compounds unusually challenging to remove. Other types of pesticides stick to soil particles, which are then filtered out. But neonicotinoids can slip past sand filters because they are polar chemicals. “They dissolve very readily in water,” LeFevre said. He invoked a chemistry aphorism: “Like dissolves like.”
This proved out as the research team looked at how effectively the university’s sand filtration system and Iowa City’s different water treatment technique blocked the three neonicotinoids studied. The university’s sand filter removed 1 percent of the clothianidin, 8 percent of imidacloprid and 44 percent of thiamethoxam. By contrast, the city’s activated carbon filter blocked 100 percent of clothianidin, 94 percent of imidacloprid and 85 percent of thiamethoxam. That finding was “quite a pleasant surprise,” LeFevre said. “It’s definitely not all bad news.”
The activated carbon filters are relatively economical, he said. In fact, after the research was completed, the university installed a similar system on its campus.
Given the study’s small sample size and geographical span, Perry said more comprehensive assessments of water supplies are needed “to determine how ubiquitous neonics are in water supplies in other parts of the country.” The chance of that happening is unclear. “There is currently no national effort to measure to what extent neonicotinoids are making it into our bodies, be it through water or food,” she noted.
It is commonly understood that over 50% of nutrients that flow into lakes are from fertilizers and pesticides we apply to our lawns and gardens. Those nutrients in turn feed the weeds in our lake that we are now spending $150,000 annually to control.
Let’s all join the effort to work together to help control the weeds in our lake by making sure that we and our landscape contractors do not use pesticides and fertilizers this season.
There are several of us who are working to find ways to fertilize our plants and to keep the pests away while also not fertilizing the lake weeds. We hope to have positive guidelines for all to implement. We hope to have this ready by the Fall season.
This week some signs have appeared on lawns indicating pesticides have been applied. I hope this message will get out to others who are getting ready to contract their Spring yard clean up. Wouldn’t it be nice if there were no additional applications this year?
A consulting group based in Michigan has developed a strategy to significantly reduce weeds in lakes in a natural manner. They developed this program after becoming frustrated with the negative impacts resulting from the use of herbicides.
The program consists of four steps. To view each step, please click below:
Step 1: Revive
Step 2: Repair
Step 3: Protect
Step 4: Sustain
This is an approach which should be considered by the Lake and Dam Committee and the WLPOA Board. The cost is relatively comparable to the cost of chemicals and it has the side benefits of reducing the “muck” in the lake as well as the weeds. The result is a healthier lake.
For additional information: HTTP: //LAKE-SAVERS.COM