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What's Wrong with Methoprene?

by Helen Roussel

Suffolk County’s Vector Control Weakens Coastal Resiliency


What is Methoprene?

Methoprene is a slow-acting bio-chemical growth inhibitor that is used by municipalities to control mosquitoes. Brand names of pesticides containing methoprene include Altosid™, Apex™, Diacan™, Dianex™, Kabat™, Minex™, Pharorid™, ZR-515 and Precor™.

Methoprene is an endocrine disrupter used to target mosquitos and control diseases by disrupting growth hormones and development of larvae - read about it HERE [1]. Evidence indicates methoprene impacts non-target species[2].

How does methoprene impact non-target species?

Research evidence indicates that methoprene effects the development of species that share similar evolutionary traits [3]. The arthropod phylum encompasses not only mosquitos but crustaceans and all other insects. Crustaceans such as lobsters and crabs are impacted by methoprene [5]. Lobster larvae has been found to be affected even by low levels of methoprene, and studies have shown that 80% of blue crab larvae is similarly affected after 10 days. And the shells/structure of both species as adults is altered, resulting in delayed molt and death[6]. The similarity in findings does indicate that methoprene affects the development of many species of arthropods impacting their ability to survive.

Fig. 1

A more hidden impact is the depletion of food webs [7],which impacts a wider variety of species such as birds and fish, starving them as there is less food. Loss of habitat is also a major factor. Furthermore, zooplankton (a critical source of food which almost all oceanic organisms is dependent upon) is to a large degree made up of crustaceans and therefore is impacted by methoprene [8]. Zooplankton is especially important around Long Island as zooplankton feeds on phytoplankton and is critical in retaining the balance in the marine food web (keeping levels of phytoplankton stable). An imbalance of phytoplankton is said to contribute to blue-green algae blooms [9].

Fig. 2 — Food Webs 

An interactive food web showing how fish (for instance) have indirect effects on populations in and around wetlands. Nature Education (2017).

Zooplankton is critical for a healthy marine environment. NASA (2017)

What About West Nile Virus (WNV)?

Data of human cases of WNV in Suffolk County indicate that infections occur in urban and suburban areas and not in wetlands.The map below shows areas sprayed with methoprene. The map below shows 5 areas where WNV occurred, and only in the area identified as Cluster 5are there significant wetlands. WNV occurs in urban and suburban areas where American Robins (the main reservoir for WNV) and Culex pipiens mosquito (the bird to human WNV bridge) can be found. Furthermore, WNV is driven by shifts of feeding behavior that is influenced by the migratory patterns of American Robins (the preferred host for Culex pipiens) [12].

 Fig. 3 — Combined map with overlays (Rochlin, 2011), (EPA, 2008).

What Can Be Done to Prevent the Spread of Mosquito-borne Disease?  

As climate change continues to alter our environment, WNV and other previously unknown diseases will continue to appear. The Culex pipiens (house mosquito) lays its eggs in polluted fresh water and degraded wetland areas around homes and built-up areas. Artificial vessels and containers that are left around in people's yards collect water which becomes polluted and creates the perfect environment for the Culex pipiens to lay its eggs.

Currently educational information includes mowing wetland plants in dry basins in urban and suburban areas. However, studies in 2016 indicated that the practice actually increases the problem. Degraded urban and suburban wetland areas are turned into mosquito breeding grounds because wetland plants are mowed [13] or cut and the dead plant does not absorb water which therefore puddles. Removing plants also means there is less habitat for birds and other potential mosquito predators.


Why are wetlands being sprayed with methoprene?

Please see the 'biting mosquito, complaint map' below which, illustrates that the majority of the complaints originate from people who live or are on vacation in wetlands areas. There is some correlation between complaints and methoprene spray locations, but absolutely no correlation between WNV outbreaks and methoprene application. Tourism spending is worth $5.5 billion [14] per year and development on wetland areas continues. As a result of over-development of wetland areas, there is less and less habitat for mosquito predators and increasing water quality issues.


The quick fix of applying pesticides is a response to phone call complaints and not a response to a threat of WNV.

Compare the 'biting mosquito complaint map' to the Water Quality Impairments map (The Nature Conservancy, 2017) Figure (5) which indicates that there are multiple issues that require sustainable approaches to deal with the impact of human activity on Long Island. 

Applying methoprene to degraded waterways is a poor quick-fix solution that increases the overall cost to biodiverse communities, wetland health and ultimately human health and the economy.

The funds need to be better spent; Rachel Carson once said "In nature nothing exists alone". Long Islands wetlands need a multi-faceted approach and an alternative nature-based scientific approach. Healthy wetlands are buffers that protect the mainland from sea level rise, floods and severe weather events (impacts of climate change).

 Fig. 4 — Suffolk County Vector Control and Wetlands Management Plan: Biting Mosquito Complaints Map

 Fig. 5 — Long Island Water Quality Impairments and 2000-2004 Cluster Hotspot Boundary and Aerial Larvicide Locations (2017).

The Social-ecosystem is Important - What is the Solution?

The health and welfare of Long Island's socio-economic systems are inextricably dependent  on healthy wetlands and healthy urban and suburban environments. Healthy ecosystems provide clean water, air and food. Wetland ecosystems support a robust tourism industry as well as serving as a buffer zone between the impacts of climate change and inland areas. Wetlands and estuaries provide food and habitat for many species of marine fish. The effects of climate change will continue to yield severe floods, increased run-off, droughts and more powerful hurricanes, which will further degrade water quality and increase algae blooms and disease. It is critical to move toward he use of less chemicals and instead adopt approaches that lead to habitat restoration that will enable ecosystems to return to levels that sustain the life around them.


Restoration of and more rigorous protection of dune areas and wetland areas are needed. Certain types of development (such as hardening of coastal shorelines) weakens resilience. Read about how healthy wetland areas saved more than $625 million in property damage during Hurricane Sandy [15] by absorbing flood water [16].

Predator breeding projects and habitat restoration programs for predator insects, birds and fish need to be established. This would attract more tourists, control mosquitos and improve the health of wetlands.


Disease Control:

Urban and Suburban Disease Control:


  • Stop the practice of cutting down wetland plants such as reeds 

  • Increase habitat restoration in degraded urban and suburban wetland areas

  • Encourage predators by launching habitat gardens for degraded areas, bird, bat and dragonfly breeding and enrichment projects 

  • Public school education programs on mosquito-borne diseases and how to prevent them as well as more public information on maintaining biodiverse gardens

  • Read the study [17] that demonstrates how wetland plants in urban and suburban areas should NOT be mowed as it creates the perfect habitat for mosquitos including Culex pipiens / WNV carrying mosquitoes: read an article about it [18]

 Fig. 6 — Andrew Mackay (2015)





[1] National Pesticide Information Center (2017), ‘Methoprene’[online]. Available at:


[2] Beyond pesticides (2017), ‘Pesticides that disrupt endocrine system are still unregulated by EPA’ [online] Available at:

[3] Tree of Life (2017),’Arthropoda’ [online]. Available at:

[4] Garcia R. N., Chung K.W., Key P.B., Burnett L.E., Coen L. D., Delorenzo M.E., (2014), ‘Interactive effects of mosquito control insecticide toxicity, hypoxia, and increased carbon dioxide on larval and juvenile eastern oysters and hard clams’, Pubmed [online]. Available at:

[5] Walker A. N., Bush P., Puritz J., Wilson T., Chang E.S., Miller T., Holloway K., Horst M. N., (2005), ‘Bioaccumulation and Metabolic Effects of the Endocrine Disruptor Methoprene in the Lobster, Homarus americanus’ Pubmed [online]. Available at:

[6] Horst M.N., Walker A.N., (1999),‘Effects Effects of the Pesticide Methoprene on Morphogenesis and Shell Formation in the Blue Crab Callinectes sapidus’, JSTOR, [online]. Available at:

[7] Pratt S. E., (2007), ‘Are Pollutants Disrupting Marine ecosystems?’, Oceanus Magazine [online]. Available at:

[8] Olmstead A.W., LeBlanc G.L., (2001), ‘Low Exposure Concentration Effects of Methoprene on Endocrine-Regulated Processes in the Crustacean Daphnia magna’ Toxilogical Sciences [online]. Available at:

[9] Suffolk County Government (2017) ‘Harmful Algae Blooms’ [online. Available at:


[10] Garcia R. N., Chung K. W., Key P. B., Burnett L.E., Coen L. D., DeLorenzo M. E., (2014), ‘Interactive Effects of Mosquito Control Insecticide Toxicity, Hypoxia, and Increased Carbon Dioxide on Larval and Juvenile Eastern Oysters and Hard Clams [online]. Available at:


[11] New York State Government (2017), ‘Governor Cuomo Announces $10.4 Million Effort to Improve Long Island Water Quality, Restore Shellfish Populations and Bolster Resilience of Coastal Communities’ [online]. Available at:


[12] Kilpatrick A.M., (2011),’Globalization, land use, and the invasion of West Nile virus’, PubMed [online]. Available at:

[13] Science Daily (2015), ‘Mowing dry detention basins makes mosquito problems worse’[online]. Available at:


[14] Long Island association (2016)

[15] Narayan S., Beck M. W., Wilson P., Thomas C. J., Guerrero A., Shepard C. C., Reguero B. G., Ingram J. C., Trespalacios D. (2017) ' The value of coastal wetlands for flood damage reduction in the Northeastern USA', Nature [online]. Available at:

[16] Akan N. (2017) 'Wetlands stopped $625 million in property damage during Hurricane Sandy. Can they help Houston?', PBS News Hour [online]. Available at:

[17] Mackay A. J., Muturi E. J., Ward M. P., Allan B. F., (2016) 'Cascade of ecological consequences for West Nile virus transmission when aquatic macrophytes invade stormwater habitats' [online]. Available at:

[18] Entomology Today (2015), ' Mowing grass in water-detention basins increases mosquito populations' [online]. Available at:

Connecticut banned methoprene spraying in 2013
It's time for New York State to do it's part to protect our coastal waterways
Contact members of the New York State Senate and Assembly and ask them to support  NYS Senate & Assembly bills A6336/S.4819.

Find your State Senator & Assembly-member here:


and here:

For more information visit:
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