Six Mile Lake2011 Summary

Weevil Biology

Native to North America and Long Lake

Original host plant is native Northern watermilfoil

Entirely aquatic, except for shoreline hibernation in

winter

Larvae and Pupae stages have highest impact

Tunnel through stem, emerge as adults

Eggs

Larvae

Pupa

Adult

Weevil-Induced Damage

Nutrient flow disrupted Loss of buoyancy = collapse Reduced biomass & plant

height Secondary infections

EnviroScience Stocking Strategy Stock multiple

years More weevils in first

year Concentrate weevil

populations in a few locations

Annual surveys: evaluate progress

Seasonal variation

YearSites

Stocked Total

Weevils

2009 S1 6,000

2010 S1, S2, S3 12,000

2011 S1, S2, S3 16,000

Survey ComponentsWeevil population density

Milfoil densityNative plant species and relative abundance

Weevil activityOverall health of milfoil

Long term data

2011 Positive Results

• Weevil life stages and damage found at all stocking sites•2011 results indicate an increase in weevil population• Found weevils at S2 which was previously undetected in 2010• Milfoil density at S2 and S3 decreased by 75% and 50% post-stocking 2011• Milfoil is well-below surface of water (1-3 feet) in stocking sites• S1 had a 50/50 mix of milfoil and native plants

Native Plant Species Seven native aquatic plant species were recorded in 2011: Clasping leaf pondweed (Potamogeton

perfoliatus), Chara (Chara sp.), Coontail (Ceratophyllum demersum), Eelgrass/Water Celery (Valisneria americana), Elodea (Elodea canadensis), Flat-stem pondweed (P. zosteriformis), Large leaf pondweed (P. amplifolius), Northern watermilfoil (Myriophyllum sibiricum), Sago pondweed (P. pectinatus), Thin pondweed (P. pusilus), White water-buttercup (Ranunculus aquatilus), and White water lily (Nymphaea spp.).

Slow start to stocking 2011 Seasonal Variability

Expected Results Milfoil growing below surface Decrease in milfoil density and

health Increase in native plant species

density

Six Mile LakeProject Considerations

2012 Proposal

Association contract for 15,000 weevils

EnviroScience will match (30,000 total) for a more aggressive plan

Address additional areas of infestation Comprehensive milfoil assessment

What you can do to help

(800)940-4025(330)688-1111

3781 Darrow RdStow, OH 44224

www.enviroscienceinc.com

Contact EnviroScience