Consultant's Report - Minnesota State Legislature

Limitations in this data set hav.e direct consequences on the ability to make
recommendations for field application of Cutrine®-Ultra and CUS04 to control D.
polymorpha larvae. As a result of these limitations, implicit and explicit uncertainty
should be considered in determining the use of Cu and Cu-based products to control
zebra mussels. Limitations and uncertainty include:
This report does not sanction the use of Cu or Cu-based products in the control of
zebra mussels. This decision is the responsibility ofMN DNR, or any other party,
with due regard to relevant permits and regulations. EERT and ERDC do not take
responsibility for actions taken by any party based upon information in this report.
• Cu toxicity data are highly dependent upon the temperature, hardness, and
alkalinity of water. These data only apply for the water quality parameters stated
in Table 1, Appendix 1. If necessary, the data can be used to model toxicity
estimates under other water quality conditions.
• Larval data only pertain to 0 - 96-h old larvae. While these are key planktonic
phases, we were not able to test Cutrine®-Ultra efficacy on later life stages.
LC99 data are modeled estimates, not observations.
• Similarly, the 95 % confidence intervals are modeled estimates, not observations.
• These tests were performed under controlled laboratory conditions. There
remains uncertainty as to the application of mussel sensitivity data to field
situations.
Recommendationsfor monitoring ofCutrine@-Ultra
We recommend daily measurements of aqueous Cu to ensure adequate control.
Accurate, field-based analytical techniques are widely available. Concentrations of
Cutrine®-Ultra should be maintained at approximately 0.3 mg CulL, should a lOx
protection factor be required. In addition, water residence time in the treated area should
be assessed and used to gauge the suitability of these data for the measured water
residence time in the treated area.
We also recommend that any Cu treatment regime be amended to reflect any
residual Cu in the water column at time of treatment, to ensure that Cu concentrations in
the water body do not exceed 1 mg CulL at any time.
Recommendationsfor monitoring D. polym01pha
We recommend regular plankton screening in the spring and summer, to monitor
for occurrence of D. polymorpha larvae in the water column. Observations of D.
polymorpha larvae during these screens may be used to initiate Cutrine®-Ultra treatment
prior to onset of 12°C water temperatures. In the absence of D. polymorpha Cutrine®­
Ultra treatment can be suspended.
In addition, regular monitoring of suitable settlement sites downstream for
emergent adult D. polymorpha populations is recommended.
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