Written By Kellie Nestrud, Biologist and Contract Manager in Louisiana
There are several different components of a successful Integrated Mosquito Management (IMM) program. The consideration of chemical resistance in the local mosquito population is one of the components. Knowing, understanding, and monitoring for chemical resistance should begin as early as possible in an IMM program. It is recommended that all IMM programs monitor their mosquito populations for resistance at the beginning of a season and as often throughout the season as thought necessary. Resistance data is most valuable when collected over time to allow for comparison and monitoring of trends. There are many methods to monitor the effectiveness of an insecticide, and program managers may need to adjust their approach from season to season.
The Centers for Disease Control and Prevention (CDC) defines that a population of mosquitoes is considered to be resistant to an insecticide if a mortality rate is less than 90%. So how would one know if they are working with a population that has resistance?
CDC Bottle Bioassay
Is it Possible to Use a Chemical Routinely and NOT Observe Resistance?
Overcoming a Resistant Population
Management by Moderation. This method is meant to maintain the susceptible genes in the overall mosquito population by using low insecticide rates, infrequent applications, and non-persistent compounds.
Goal: Genetically speaking, you are trying to give the local population a chance to “recover.”
Management by Saturation. The approach is just as it sounds. The population is saturated with sufficient doses so that no survivors remain. This method can be especially useful during the early stages of selection of resistant genes.
Goal: To put a break in the resistance and not let it continue to the next generation.
Management by Class Rotation. An additional option, for continuing to successfully manage a mosquito population with known chemical resistance, is to change to a different class of chemical that uses a different Mode of Action (MoA). There are many EPA approved pesticides available for the use of mosquito control. However, there are limited classes of chemicals - only three (3). This is important because each class of chemical has a unique MoA, which is the method of interrupting a mosquito’s vital processes that result in its death. But with only three options available, and typically a significant price increase between classes, it is important that this method is used responsibly.
Goal: To prevent further growth of resistance in a population by introducing a chemical that has an alternative process to attack the mosquito’s body functions and result in death.
Potential Resistance Phenomena
Cross Resistance means that the population is not only resistant to one insecticide of a particular class, but also to other insecticides in the same class, even when that population has never been treated with that insecticide.
Multiple Resistance refers to separate detoxification mechanisms for unrelated insecticides are present resulting in a mosquito population that is resistant to different classes of insecticides (with different MoA) which makes chemical control of that population extremely difficult.
Behavioral Resistance. There is also documentation of a phenomenon called Behavioral Resistance where mosquitoes have been found to no longer rest on surfaces that have been treated with a residual adulticide chemical in the past.
Ignoring the Problem
Advice: Monitor, Monitor, Monitor
VDCI is committed to public education and spreading awareness throughout the U.S. about the dangers of mosquito-borne diseases and their preventability, with the overarching goal of reducing illness and fatality statistics in 2018. Our dedicated and experienced team works tirelessly to prevent the spread of mosquito-borne diseases in all of the contracts we service. If you would like more information about any aspect of an Integrated Mosquito Management (IMM) Plan, including mosquito surveillance, disease testing, adult control, or aerial applications, please contact Vector Disease Control International (VDCI), and we will help you get started immediately.
Kellie Nestrud is a Contract Manager for Vector Disease Control International (VDCI) in our Delta Region and has been a member of the VDCI family since 2002. Kellie holds a degree in Biology with a minor in Chemistry from Louisiana Tech University. Her experience includes research trials for new chemicals, bottle bioassays for tracking chemical resistance in mosquito populations, and participating in Emergency Response missions following hurricanes or major flooding. She is one of the few privileged to study mosquito identification under the late Dr. Richard Darsie Jr. (Co-author of Identification and Geographical Distribution of the Mosquitoes of North America, North of Mexico) at Florida Medical Entomology Laboratory (FMEL). She can be reached through the VDCI website or by calling 800.413.4445.
Since 1992, Vector Disease Control International (VDCI) has taken pride in providing municipalities, mosquito abatement districts, military bases, industrial sites, planned communities, homeowners associations, and golf courses with the tools they need to run effective integrated tick and mosquito management. We are determined to protect the public health of the communities in which we operate. Our tick and mosquito management professionals have over 100 years of combined experience in the field of public health, specifically vector disease control. We strive to provide the most effective and scientifically sound mosquito surveillance and control programs possible based on an Integrated Mosquito Management approach recommended by the American Mosquito Control Association (AMCA) and Centers for Disease Control and Prevention (CDC). VDCI is the only company in the country that can manage all aspects of an integrated tick and mosquito management program, from surveillance to disease testing to mosquito aerial application in emergency response situations.
Contact the professionals at 800.413.4445 for all of your integrated tick and mosquito management needs.