Some suggested/recommended changes to draft general NPDES permit re: mosquito control spray 

practices 

Meredith William H. (DNREC) 

to: 

Linda Boornazian, Doris Gray, Allison Wiedeman, Jack Faulk, William Jordan, Susan Lewis 

01/27/2010 07:52 PM 

Cc: 

David Rise 

Show Details 

History: This message has been forwarded. 

EPA folks – as I indicated in Dallas for some follow‐up that I’d provide, below are some

suggestions/recommendations for modifying 3 sections of the draft general NPDES permit pertaining to mosquito

control spray practices:

  

2.2.1.3.4   [Currently reads] Use larvicides as the primary pesticide for mosquito or aquatic nuisance insect

control;

  

Suggested change to:   In situations or locations where practicable and feasible for efficacious control, use

larvicides as a preferred pesticide for mosquito or aquatic insect control when larval action thresholds have been

met;

  

This change would more realistically recognize that there’ll be many situations where from the start a MCD would

quickly reject the notion of first trying to larvicide, but almost immediately move onto adulticiding – e.g. for a

coastal community bordering expansive areas of breeding salt marsh that would require larviciding thousands or

tens‐of‐thousands of nearby or even distant wetland acres to reduce mosquito problems for the community (and

hence a lot of product use in water), versus more surgically adulticiding as needed only a few hundred acres within

or nearby the community (which might primarily be upland without much water, albeit you might also then be

spraying directly over where people live, work or recreate).  I realize that the current wording in the draft permit

might please or be some type of “sop” to the “environmentalists,” but it really makes little ecological or

environmental sense, and in many locations would be infeasible or impracticable to implement.  Also please be

sure wherever else in the draft permit such dubious primacy is touted that this too gets modified as

suggested/recommended above.

2.2.1.3.5    [Currently reads]   Use adulticides only where the adult action threshold has been met and/or under

emergency condition (e.g. flooding, disease outbreak);

  

Suggested change to:  In situations or locations where larvicide use is not practicable or feasible for efficacious

control, use adulticides for mosquito or aquatic insect control when adult action thresholds have been met,

and/or under emergency conditions (e.g. flooding, disease outbreak);    

  

See my rationale above for 2.2.1.3.4

2.2.1.3.6    [Currently reads]   Do not apply adulticides over waters of the U.S. except when necessary to target

areas where adult mosquitoes or insect pests are present, and when weather conditions will facilitate movement

of pesticide product away from the water to minimize discharges into the water.

  

Suggested change to:   Do not apply adulticides over waters of the U.S. except when necessary to target areas

where adult mosquitoes or insect pests are present and adult action thresholds have been met, as may be an

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occasional or even frequent need in or over some wetland areas, to be done in consideration of wind direction

that facilitates applied product to reach targeted treatment areas.

  

The current wording in the draft permit is lifted directly from PRN 2005‐1, whereby the second part of the current

read above apparently was a last minute “sop” to the “environmentalists” in crafting PRN 2005‐1, perhaps as

some type of “trade‐off” for the EPA’s having realistically consented to the first part of the statement above (and

the second part above surely caught the mosquito control community by surprise!), which in many situations

makes little sense and can be counter‐productive to both good environmental protection and wise pesticide

stewardship.  I recommend that you don’t perpetuate this problem as found in the second part above from PRN

2005‐1 by then repeating such language in the new permit.  In part my suggested alternative verbiage above also

comes from my speaking with EPA’s David Rise while in Dallas.  

The window of opportunity in terms of adult mosquito emergence and adult population occurrence over a marsh

can be quite limited for effectively applying adulticides before adult mosquitoes emigrate landward and spread

out over vast expanses of uplands.  In many situations and locations, you’ll want to adulticide in timely manner

over only a few hundred acres of breeding marsh when and where newly emerged adult mosquitoes are still

congregated, doing such by utilizing whatever wind direction at time of spraying will yield most effective control

(whether any additional spray drift beyond the target area then eventually settles out into water or not).  You thus

want to apply adulticides in timely manner before adult mosquitoes move off‐site to occupy new areas, which if

not achieved might then require that thousands or tens‐of‐thousands of acres both nearby and distant be

adulticided, with the latter often being a mixture of uplands and other types of wetlands.  Possibly having to wait

to apply adulticides until you have a wind direction that allows product to reach the target area, and then for any

further spray drift beyond the target area to eventually settle out away from water (whether away from other

wetlands or open water bodies), will often cause you to miss spraying over natal marshes in timely manner to

knock‐down emerged adult populations before they widely disperse.  Please also understand that the purposeful,

relatively long‐distance spray drift of adulticides applied for mosquito control causes great dispersal of any

product that eventually settles out into water bodies (whether into wetlands or open waters), and hence very low

concentrations of product within the water column, and only deminimus if any impacts to non‐target aquatic

organisms.            

Thank you for considering these suggestions/recommendations.

  

Regards,  

  

BILL MEREDITH

Environmental Program Administrator

Delaware DNREC

302‐739‐9917

  

  

  

  

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