Mosquito Control Chemical Guide
2003 West Nile Virus Response Plan
Prepared by:
Emilio DeBess DVM, MPVM
State Public Health Veterinarian
This document was created with the assistance of the West Nile Virus (WNV) working group
Joe Engler ,USFWS
Jay Kravitz, MD Washington County
Nancy Munn, NOAA Fisheries
Phil Rossignol ,Oregon State University
Bob Sallinger, Audubon Society
David Sjogren, Fennimore
Jill Townsen, (for Darleene Judd) Oregon State University
David Turner, Multnomah County Vector
Mace Vaughan, Xerces Society
Curt Zonick, Metro-Parks
Introduction
Because of concern in Oregon about possible West NileVirus (WNV) activity in 2003, it is likely that some communities will begin or
increase mosquito control programs this year. Consequently, Oregon Department of Human Services recommend that local
governments that conduct mosquito control programs should emphasize the methods that are most effective at controlling the
anticipated primary mosquito vectors (carriers) of WNV.
Please be aware that all pesticide applicators for mosquito control should be licensed by the Oregon Department of Agriculture
(ODA). The only exceptions are if one applies pesticide(s) to one's own residential property.
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Control of the West Nile Virus Mosquito Vector
Control of Culex spp. larvae is a priority: Although WNV has been detected in several species of mosquitoes, about 70% of the
positive samples have been from Culex pipiens (the house mosquito) and related species of Culex. The house mosquito breeds most
prolifically in stagnant water that has a heavy organic content. In urban areas, catch basins, artificial water-filled containers like used
tires and poorly-draining ditches are common production sites for Culex spp. mosquitoes. Additionally, most of the house
mosquitoes present in a community were produced locally, because the house mosquito does not fly more than about 1 to 2 miles
from its production site. In contrast, the inland floodwater mosquito, Aedes vexans can fly 20 or more miles from where it hatches,
particularly along prevailing winds. Although floodwater mosquitoes can be a nuisance to the public when they are abundant, they are
currently believed to be minor carriers of WNV.
The most effective method of mosquito control is "larviciding," or the treatment of locations where mosquito larvae are present, such
as the water impounded in the bottom of “catch basins” (storm drains). Catch basins may be found along streets, in parking lots and
sometimes in backyards. Because catch basins are a major source of the house mosquito in urban areas, the Department recommends
that catch basins be treated at least three times during the summer to control Culex spp. mosquitoes. Ideally, communities should treat
catch basins and other locations that produce Culex spp. mosquitoes as often as determined by necessary inspection and according to
insecticide label directions. However, a minimum response by a municipality would be to treat catch basins and other Culex
production sites three times during the summer (June, July and August). Please see Table 1 for a list of mosquito larvicides. This
would reduce numbers of vector mosquitoes during late summer, the period that seems to be of greatest risk to humans. We
recommend that local officials review the references about mosquito control found in Table 2, particularly the CDC /USEPA Joint
Statement on Mosquito Control and Integrated Methods of Mosquito Control.
Spraying for Adult Mosquitoes: Adult mosquito control (also called "fogging," "spraying" or “adulticiding”) is the method of
mosquito control that is most familiar to the public. However, the aerosol fog kills only mosquitoes that contact insecticide droplets;
the fog soon dissipates. Although the local mosquito population is reduced for a few days, fogging does not prevent mosquitoes from
re-entering the area. Because only a part of the local adult mosquito population is reduced only for a few days by fogging,
municipalities should give priority to larval mosquito control of Culex spp. mosquitoes. Nonetheless, when the risk of human disease
is present, the only method that will reduce the population of WNV-infected mosquitoes throughout a community is adulticiding. This
may be the best option available to those communities lacking an organized mosquito control program. However, every effort should
be made to inform the public when treatment for adult mosquitoes is planned. An informed public will better understand the measures
being taken and will be able to take precautions to limit their exposure to pesticides.
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Non-chemical Mosquito Control: Mosquito larvae or "wrigglers" must live in still water for five or more days to complete their
growth before changing into adult biting mosquitoes capable of transmitting disease. Often, the number of mosquitoes in an area can
be reduced by removing sources of standing water around residences. For example, hundreds of mosquitoes can come from a single
discarded tire. Local agencies should inform the public how to prevent mosquito production around residences and prevent mosquito
bites:
1. Get rid of old tires, tin cans, buckets, drums, bottles or any water-holding containers.
2. Keep drains, ditches, and culverts free of weeds and trash so water will drain properly.
3. Keep roof gutters free of leaves and other debris.
4. Empty plastic wading pools at least once a week and store indoors when not in use.
5. Unused swimming pools should be drained and kept dry during the mosquito season.
6. Change the water in birdbaths and plant pots or drip trays at least once each week.
7. Store boats covered or upside down, or remove rainwater weekly.
8. Make sure ornamental ponds are well maintained, and are stocked with fish.
9. Repair window screens.
10. When outdoors in the evening or when mosquitoes are biting, use personal protection
measures to prevent mosquito bites (proper use of insect repellent and appropriate
clothing).
In summary, local agencies that conduct mosquito control should give highest priority to eliminating breeding sites and
larviciding. Elimination and treatment of Culex spp. mosquito production sites will help municipalities protect Oregon citizens
from mosquito-borne West Nile virus.
Mosquito larvicides for use in West Nile virus Response.
Always read and follow all current pesticide label instructions. If any information in these recommendations disagrees with the
pesticide label, the label instructions must be followed. Use of a product name does not constitute product endorsement. All
pesticides must be registered with USEPA and the ODA.
Common Mosquito Larvacides registered for use in Oregon.
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These materials offer residual control.
Active Ingredient Bacillus sphaericus
Vectolex CG
Vectolex WSP
Vectolex WDG
Active Ingredient Methoprene
Altosid Pellets
Altosid Briquets
Altosid XR Briquets
Altosid XRG
Altosid ALL
These materials offer no residual control.
Active Ingredient Bacillus thuringiensis var. israelensis
Vectobac G
Vectobac CG
Vectobac 12AS
Aquabac G
Aquabac CG
Mosquito Adulticides for use in West Nile Virus Response.
Applications of pesticides for the control of adult mosquitoes should only be made by personnel properly trained and holding
an Oregon State Department of Agriculture Public Health Pesticide Applicator license. Fogging for adult mosquitoes should
ONLY be conducted at the proper time when mosquitoes are most active, usually evening or early morning, and under
appropriate environmental conditions (such as temperatures from 60 to 85 degrees Fahrenheit and low wind speeds). For ultra-
low volume (ULV) spraying units to control mosquitoes, they MUST be serviced so they produce a proper droplet size
spectrum. Please consult the pesticide label and manufacturer's recommendations for further information
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Common Mosquito Adulticides registered for use in Oregon.
Tier 1
Active Ingredient Pyrethrin
Pyrenone 100
Pyrenone 25-5
Pyrenone 50
Pyrenone Crop Spray
Pyrocide Mosquito Adulticiding Conc.
These materials offer no crop restrictions or setbacks to water.
Pesticide products containing pyrethrins usually contain a synergist such as piperonyl butoxide (PBO). PBO’s work by
restricting an enzyme that insects use to detoxify the pyrethrins. A synergist allows the insecticide to be more effective.
Pyrethrins have a soil half life of 12 days. They have an extremely low pesticide movement rating because they bind tightly to
soil. Pyrethrins are unstable in light or air, and are rapidly degraded in sunlight at the soil surface, and in water. Pyrethrins are
highly toxic to fish, tadpoles, honeybees and many aquatic invertebrates.
Tier 2
Active Ingredients Permethrin, Resmethrin and Sumithrin
Anvil 10+10 ULV
Anvil 2+2 ULV
Aqua Reslin
Permanone 10% E.C.
Permanone 31-66
Permanone Ready to use Insecticide
Scourge 18% + 54%
Scourge 4% + 12%
Permethrin, Resmethrin and Sumithrin have setback restrictions to water, and do contain restrictions on applications to some
crops. These materials also contain PBO’s. The typical half life of these materials in soil is 30 days. These materials have an
extremely low potential to move in soil. They are unlikely to contaminate groundwater because they bind tightly to soil
particles. In water, and on soil surfaces these materials are degraded by sunlight. These products are highly toxic to fish, bees
and many aquatic invertebrates.
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Tier 3
Active Ingredient Malathion
Fyfanon ULV (Malathion 96.5%)
Malathion ULV
Atrapa 96.5
Malathion does have setbacks restrictions to water, but does not contain any crop restrictions. Based on its physical-chemical
properties, malathion shows little persistence in soil and water. This product is highly toxic to fish, bees and many aquatic
invertebrates.
Active Ingredient Dibrom
Trumpet EC
Dibrom Concentrate
This product can be applied by conventional ground based ULV applications, however it is best suited as an aerial applied
adulticide. This product does not have setback restrictions to water, is labeled on over 25 crops and has a .5 ppm tolerance as
established by the EPA for all crops. Naled shows little persistence in soil or water. This product is highly toxic to fish, bees
and many aquatic invertebrates.
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Table 1
Aqua Reslin Permanone Scourge Anvil Pyrenone Mosquito Mist
Active Ingredient Permethrin Permethrin Resmethrin Sumithrin Pyrethrin Chlopyrifios
Class of Insecticide Pyrethroid Pyrethroid Pyrethroid Pyrethroid Pyrethrin Organophospate
AI% 20 18 10 5 19.36
PBO % 20 66 54 10 25
Max Label Rate 0.007lb of ai/acre 0.007lb of ai/acre 0.007lb of ai/acre .0036lb of ai/acre 0.0025lb of ai/acre 0.01lb of ai/acre
Set Back 100 feet 100 feet no no no no
Corp Tolerance no no no no yes no
Photodegredation Stable Stable less than 4 hours 48 hours Rapid
Photolysis Stable Stable 37 minutes 200 days Rapid
Rainbow trout LC50 Rainbow trout LC50 Rainbow trout LC50 Rainbow trout LC50
Fish Toxicity (96h) = 2.5 ug/l (96h) = 2.4 ug/l (96h) = .0167 mg/l (96h) = 54 ug/l
Specific Gravity 1.015 1.11 0.99 0.884 0.884
Oral LD50 1000 mg/kg rat 1250 mg/kg rat 2700 mg/kg rat >5000 mg/kg rat >5000 mg/kg
Dermal LD50 >5000 mg/kg rabbit 2,020 mg/kg rabbit >2000 mg/kg rabbit >5000 mg/kg rabbit >5000 mg/kg
Inhalatin LC50 -
4hr >2.87 mg/L rat 4.39 mg/L >2.64 mg/L rat 1.21 mg/L - 4hr. Rat >4.93 mg/L
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Table 2 DIBROM TRUMPET
Active Ingredient Naled Naled Fyfanon Atrapa Baytex - FL only
Class of Insecticide Organophosphate Organophosphate Malathion Malathion Fenthion
AI% 87.4 78 Organophosphate Organophosphate Organophosphate
PBO % 0.0 0.0 96.5 96.5 95
Max Label Rate 0.10 lb of ai/acre 0.10 lb of ai/acre
Set Back no no .05lb of ai/acre .05lb of ai/acre 0.1lb of ai/acre
Crop Tolerance yes yes no no
Photodegredation <24 hours <24 hours yes yes no
Photolysis <24 hours <24 hours
Rainbow trout LC50 Rainbow trout LC50
Fish Toxicity (96h) = .195 mg/l (96h) = .195 mg/l
Specific Gravity 1.79 1.67
Oral LD50 50-100mg/kg rat 50-100mg/kg rat 1.23 1.24
Dermal LD50 2-5000 mg/kg rabbit 2-5000 mg/kg rabbit 5500 mg/kg rat 1950 mg/kg rat 405 mg/kg rat
Inhalatin LC50 -
4hr 1.2 mg/L - 4hr. Rat 1.2 mg/L - 4hr. Rat 8790 mg/kg rabbit >2000 mg/kg rat 586 mg/kg rabbit
87.4 78 >5.2 mg/L rat >2.05 mg/L rat .454 mg/L rat
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Table 3 Mosquito Control References
Agency Title Web Site Address
ODHS West Nile Virus Web Site http://www.dhs.state.or.us/publichealth/acd/wnile/index.cfm
CDC DEET Insect Repellents http://www.cdc.gov/ncidod/dvbid/westnile/qa/insect_repellent.htm
CDC / US EPA http://www.epa.gov/pesticides/citizens/mosquitojoint.htm
Joint Statement
CDC and on Mosquito Control
USEPA Pesticides and Public Health: http://www.cdc.gov/ncidod/eid/vol7no1/rose.htm
Integrated Methods of Mosquito
Management
Pesticides and http://www.epa.gov/pesticides/citizens/pmcfs.pdf
Mosquito Control http://www.epa.gov/pesticides/factsheets/skeeters.htm
Using Insect http://www.epa.gov/pesticides/citizens/insectrp.htm
USEPA Repellents Safely
Larvicides for http://www.epa.gov/pesticides/citizens/larvfs.pdf
Mosquito Control http://www.epa.gov/pesticides/citizens/larvicides4mosquitos.htm
Synthetic Pyrethroids for http://www.epa.gov/pesticides/citizens/synpyfs.pdf
Mosquito Control http://www.epa.gov/pesticides/citizens/pyrethroids4mosquitos.htm
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