Where is West Nile virus this year?

If it seems you're hearing less about West Nile virus (WNV) this summer, you may not be imagining it.  Although mosquitoes have been abundant in north Texas this year, for some reason the virus has remained relatively quiet.

Where has WNV gone?

A paper written by epidemiologist Dr. Wendy Chung and colleagues in 2013 may offer some insights on the absence of the virus this summer. Those of us who lived in Dallas in 2012 may remember that summer as the worst human outbreak of WNV ever.  Nearly 400 cases were reported in Dallas County alone, and 19 people died of the disease. The epidemic was so bad that Dallas county resorted to spraying the entire county for mosquitoes by plane--something not seen in north Texas since an encephalitis outbreak in 1966.

Chung and colleagues charted the course of the disease during 2012 and saw high infection rates of mosquitoes early in the summer, followed by a rapid increase in human cases. Looking back over previous years and case numbers, the researchers concluded that an unusually mild winter followed by rainfall patterns ideal for mosquito breeding in the spring (and a very hot summer--West Nile virus multiplies quickly in mosquitoes at higher temperatures) created ideal conditions for an outbreak.

So what's different about 2019? We had a relatively mild winter, with only three days at or below 28° F, and a wet spring--both conditions mosquitoes love. But the summer, at least by Dallas standards, has so far been cool.  Until this week, the DFW Airport weather station saw only two days over 100° F. By the end of July the area usually has experienced more than seven days over 100° F.

These graphs show 2019 mosquito abundance and Vector Index (V.I.) estimates compared to previous years. Although mosquito numbers are high this year, the V.I. has remained low for both Tarrant (=Fort Worth-top) and Dallas counties (bottom). In 2012 the V.I. exceeded the danger level of 0.5 for multiple weeks (blue dotted line). Source: Tarrant County Public Health and Dallas County Health and Human Services.

Predicting WNV

One of the tools used by health departments to predict disease risk for WNV is a statistic called the vector index (V.I.).  The V.I. is calculated weekly from mosquito trap data, and combines information on both average abundance of Culex quinquefasciatus (the main carrier of WNV) and disease incidence in the trapped mosquitoes.  A V.I. of 0.5 or higher for two or more weeks is considered a crisis indicator by some health officials.

The graphs shown here are provided by epidemiologists in Dallas and Fort Worth, and show both mosquito abundance and V.I. estimates for both counties. Despite higher mosquito numbers, the V.I. hasn't ventured above 0.1 for either Dallas or Tarrant counties this summer. Most of the season the V.I. has been closer to zero, hence less need for mosquito spraying and fewer people getting sick. In Dallas county this year there have been no human cases of WNV. Tarrant County (Fort Worth) reports only one case this year with a very low V.I., near zero most weeks (top graph).

According to statistics from the Texas Department of State Health Services, low WNV incidence seems to be true for the whole state this year with no reported human cases as of the end of July.  Harris County (Houston) also reports a light year for WNV, according to the acting director of Mosquito and Vector Control, Chris Fredregill.

Looking Ahead

With this week's string of 100° days in many areas will risk go up?  Certainly West Nile virus remains a threat to all of us through the end of the summer and into the fall; but this late in the season the chance of a major outbreak is probably low. On the other hand, hot weather favors the virus. It's no time to forget about mosquitoes. I expect Aedes mosquitoes (yellow fever mosquito and Asian tiger mosquito) to become more abundant after last weekend's rains.  This week is a good time to get out and dump standing water.  Although Aedes mosquitoes are not major disease risks, they cause most of the itchy mosquito bites we get during the day--and we don't want that.

Why Surveillance Reports?

Integrated pest management is just as relevant for mosquito control as it is for all other forms of pest control.  One of the principles of IPM is to base treatments on pest numbers.  Because mosquito monitoring is expensive and requires special expertise beyond what most PMPs possess, few companies monitor mosquito numbers or disease. However, high quality data may be available from your local health authorities, depending where you live. A pest management company can use this data to alert customers to times of higher disease risk and changes in mosquito abundance.

Every community's mosquito situation will be different.  If you are doing business in a larger metropolitan area, or a mosquito control district, you may have access to the kind of data shown here. To find out, contact your local or regional health department and ask if they provide reports of mosquito abundance and disease prevalence.

In Dallas, weekly reports may be obtained by emailing Epidemiology@dallascounty.org and requesting to subscribe to the weekly Arbovirus Surveillance Report. For Tarrant County, email RWHill2@tarrantcounty.com and request to receive the Arbovirus Surveillance Report Weekly.  Unfortunately, not all counties have equivalent reporting systems. Harris County provides mapping of areas with virus detection.  And the Texas Department of State Health Services provides weekly reports throughout the summer for the whole state.

An additional source of information for both PMPs and your customers is the Mosquito Safari website. At the Safari you can take a virtual tour of a field and a backyard and learn important facts about mosquitoes. 

If you need more intensive training, our Extension medical entomologist, Dr. Sonja Swiger, is offering classes this year for pesticide applicators wanting to prepare for their Public Health (Category 12) license.  In the fall she also offers several 3-day Master Vector Borne Disease Management Courses around the state.  To learn more, or to register, go to https://livestockvetento.tamu.edu/workshop-registration/ .

Bugs and basil: Insecticides and veggies don't always mix

Who wants to eat insecticide?  Not me, and I'm guessing certainly not your customers.

So if your company does residential pest control, are your employees trained to know what to do when they encounter a vegetable garden, fruit or nut tree in a backyard?  And are they trained to answer a customer's questions about the safety of their insecticides around vegetables or herbs?  

Do your employees know what to do when encountering vegetables, herbs 
or other food plants around a home? Asking a customer about their edible
plants might save that account. Photo by Jeff Raska. 

I'm guessing this subject is not commonly addressed in technician training classes. I was asked by an industry sales representative this week: "Is it appropriate for a technician to be recommending that a homeowner simply wash their vegetables after having their yard treated for mosquitoes, or should the vegetables should be thrown away?"

The answer to this question depends on whether the plants were directly exposed to the spray and what the label says.

I did a quick review of the common mosquito adulticides used in backpack sprayers.  None of them allow application to edible plants.  The Suspend® Polyzone label, for example, says “do not apply this product to edible crops.” The Fendona® label says to not use on vegetable gardens.  Some make no mention of vegetables or edible crops at all.  And when it comes to edible plants, if application is not explicitly mentioned, it's not allowed.

Will pesticides make a plant toxic?

Of course many insecticides, including some of the active ingredients in your tool kit, are used legally on crops all the time by farmers. This is allowed by the EPA only if that pesticide has been granted a tolerance for a given crop, and certain days-to-harvest intervals are followed.  These rules work to ensure that any pesticide residues left after a pesticide application are below levels of concern for human health. The 2016 Pesticide Data Program survey by USDA shows that this system works. Out of 10,000 market food samples analyzed in the study, over 99 percent had residues well below the EPA established tolerances. More than 23 percent had no detectable pesticide residue.

So insecticide residues on plants are not necessarily toxic, especially when label directions are followed and adequate time passes to allow the product to naturally degrade. The products we use in pest control may be the same active ingredients used by farmers; but they may differ in concentration and formulation. Most importantly, pest control insecticides do not carry food-treatment labels so they cannot legally be used on edible crops.

Talstar® products, for example, consist of the active ingredient bifenthrin, the same active ingredient used by farmers and even home gardeners under a variety of trade names. The Talstar® P label for mosquito control, however, says "not to apply to bearing fruit or nut trees or vegetables or edible crops." To a law judge it won't matter whether other formulations allow application to food crops. To a judge enforcing FIFRA requirements, you must follow the label on the product you are using.

Spray contamination 

If an insecticide is deliberately sprayed on an edible crop or plant, and the product is not labeled for such use, the plant would not considered safe by EPA standards. The implication is that all of the plant, or at least the edible parts, should be thrown away. Your customer could replant, of course, unless prohibited by the label.

Backpack mistblowers are commonly used
for applying residual insecticides to mosquito
resting sites; but mists should be applied carefully
to avoid drift onto fruit and nut trees and
vegetable gardens.

Labels generally do not, however, prohibit use of these products in the vicinity of a vegetable garden. I assume this means that if you take care to keep sprays directed away from vegetable gardens, any incidental drift from nearby spraying with a coarse spray, aerosol or mist generator equipment should not be a problem. Likewise, thermal foggers and ULV applications used nearby should leave insignificant residues as long as the application orifices are directed away from edible plants at all times.

Of course applicators should always be aware of weather conditions and the locations of edible plants.  If wind is blowing toward a garden, upwind applications should be avoided.

So what should you do if a fruit, nut, vegetable or herb is is accidentally over-sprayed? Such a plant should be pulled, or else the produce should be left uneaten or discarded, by the customer.

Systemic insecticides

Some insecticides are "systemic," meaning they have enough water solubility to be taken up by plant roots and translocated to other parts of the plant. Although the EPA allows some systemic insecticides on crops, in general systemics are not labeled for use on food crops because they can leave residues in edible plant tissues that do not quickly degrade.

Insecticides containing neonicotinoids and acephate are examples of PMP insecticides that may be systemic in plants. These include products like Merit®, Premise®, Transport®, Tandem®, Alpine®, Temprid®, Orthene® and others.  Herbs and other root or leafy vegetables exposed to systemic insecticides should be considered contaminated for the season and should not be consumed.

Some termiticides can also be systemic in plants, leading to concerns about vegetable gardens planted next to homes treated for termites. Fipronil, for example, is slightly systemic in some plants; and the Termidor® SC label says not to "apply around edible plants."  The label does not say explicitly how far away an edible plant must be, although the Premise® 2 label (whose active ingredient, imidacloprid, is much more water soluble) is more specific. It says to "not treat within a distance of one foot out from the drip line of edible plants."  The Premise® guideline, therefore, is probably a good, conservative guidelines for all termiticides. Keep the outermost leaves of garden plants at least a foot away from any soil-applied termiticide and you should be OK.

Washing

Regarding washing, your technician may want to suggest vegetable washing to a concerned customer whose nearby yard or house perimeter has been treated with an insecticide spray.  Washing is a good idea whether pesticides have been used or not. The best washing technique includes a pre-rinse with a 10% vinegar solution (for germ control) followed by 30 seconds of tap water.  This is a great way to remove urban dust, microorganisms and traces of pesticides from vegetable and fruit surfaces.  

Would you recognize an edible plant?

Lastly, can you and your technicians tell a basil from a begonia, a mint from a marigold, or a pear from a poplar? Any applicator wanting to follow label directions around a home needs to be aware of what plants are present. We all don't have to be botanists, or know all the local tree species; but we should recognize the most common fruit and nut trees, herbs, and vegetables. Would you know what the common herbs sage, basil or rosemary look like? Sounds like a good exercise for training day.

When visiting a residence the first time, ask your customer if they have any herbs, fruit trees, nut trees or vegetables that you need to be aware of. Today's gardeners are more likely to plant edible plants within flower gardens, so you might have a basil plant or a tomato plant growing among the daisies. Assume your customers are organic in their vegetable garden and avoid these areas accordingly.

Believe me, your customers will appreciate any extra consideration you give to their home gardens. Treat them well and they might even greet you at the door with a big bag of zucchini.

Keeping up with mosquitoes

Every knowledgeable PMP knows that assessment and monitoring is a crucial part of integrated pest management (IPM). Yet practically no one in the mosquito control business monitors mosquitoes. Why is that?

BG Sentinel traps are among the most popular
traps for sampling nuisance biting mosquitoes
like Asian tiger and yellow fever mosquitoes.

Well, mosquito surveillance isn't easy. It's time consuming, requires expensive sampling equipment and specially trained personnel.  Disease surveillance means sending mosquitoes to an outside laboratory or else conducting expensive, highly technical lab tests. So, it's no surprise, really, that few pest control companies include monitoring services, beyond perhaps backyard inspections for breeding sites.

Yet, monitoring remains important to any PMP wanting to implement an IPM/IMM program.  Without monitoring you don't know what mosquitoes are biting, what diseases are circulating, and when human risk is highest.  So what's a mosquito technician to do?

Good news. Many counties, mosquito abatement districts and cities have area-wide mosquito surveillance programs.  While not necessarily focused on your customer's property, these area-wide programs are often quite good. Some even provide neighbor-hood level detail in their public reports.  They may chart Aedes mosquito numbers collected from traps like the carbon dioxide-baited BG Sentinel trap.  And they may provide both Culex mosquito numbers and disease prevalence from gravid traps.

The gravid trap is an especially powerful monitoring tool.  West Nile carrying Culex mosquitoes are drawn to these traps like cats to catnip. They are typically baited with polluted water known as "stink water." While every health department has their own formula for stink water, it's usually made by steeping grass clippings in water for 2 weeks or so.  The foul smell of the water draws gravid female mosquitoes as they seek stagnant water for egg laying.  Gravid traps help health departments measure the number of potential WNV-carrying mosquitoes present.  Mosquitoes collected in these traps are also collected into groups, or "pools," and sent to laboratories for virus testing. Some health departments publish this data in up-to-the-week reports that can tell you and your customer about their local, seasonal risk for West Nile and related viruses.

Gravid traps consist of a tray with "stink water," with a suction
trap positioned a few inches above the water. Female mosquitoes
drawn to the water for egg-laying are sucked into the trap, where
they are collected, counted and prepared for testing.

If you live in or near one of these health departments you should be able to get useful information about your community's mosquito status by visiting their website. Some health departments even provide weekly email updates on West Nile virus and Zika surveillance. Usually all you have to do is ask to subscribe to these reports.  For those of you in north Texas, the Dallas County Health and Human Services (DCHHS) and Tarrant County Public Health departments offer some of the best mosquito epidemiology reports I've seen.  To see a sample report, click here.

There's a lot of data in these reports, but some of the key things I look for include the following.  Where in my community has WNV been detected in mosquitoes? How abundant are Aedes mosquitoes (these are the daytime biting mosquitoes most noticed by your customers)? How abundant are Culex mosquitoes (responsible for transmitting WNV to people)?  And how is the Vector Index changing?

A July 2018 graph from Dallas County Health and Human Services shows the average abundance of West Nile virus
(WNV) mosquitoes, and a calculated Vector Index (V.I.) in both 2012 and to date in 2018.  A V.I. greater than 0.5
indicates high risk of a WNV epidemic, and may serve as a threshold for aerial spraying against mosquitoes. 
The blue dotted line is the V.I. from 2012, the year of the most severe WNV outbreak in Dallas with over
400 cases and 20 deaths. This year's data (in red) shows high mosquito abundance, equivalent to 2012,
but a relatively low V.I. suggesting that human risk from WNV is still relatively low.  Graphs like these
provide a weekly snapshot of public health risk due to mosquito-borne disease.

The Vector Index (V.I.) is a mathematically calculated number that combines information about both mosquito abundance and percent of mosquitoes carrying the West Nile virus.  If numbers of mosquitoes are high, but disease incidence is low, the V.I. will show low risk.  If mosquito numbers and disease incidence are high, the V.I. will be high.  The DCHHS considers a V.I. of 0.5 or higher to constitute an unacceptable high risk of mosquitoes. For Dallas county a high V.I. will trigger emergency public health measures, possibly including aerial spraying of insecticides.

Most of your customers will likely not be familiar with health department data, nor will they understand its interpretation. But by taking the time to get access to the data, and understanding its significance, your company can serve as an educational bridge to your community. By letting customers know when disease incidence and mosquito abundance is highest, everyone is reminded of when to take special steps to avoid mosquito contact, and the importance of their own mosquito control.

It's often said that information is power. Whether you include residential mosquito control as a special service, or simply an add-on benefit to your regular customers, you owe it to them to be informed about what mosquitoes are doing in your community.  A call to your local health department can provide you with a wealth of public health data, that can make you more a powerful advocate for your clients.

Some Texas and national WNV and mosquito information can be accessed online at:

• Dallas County: http://www.dallascounty.org/department/hhs/epistats.html
• Tarrant County: http://access.tarrantcounty.com/en/public-health/epidemiology-and-health-information/health-data-and-information/west-nile-virus/2017-arbovirus-season.html
• Harris County: http://publichealth.harriscountytx.gov/Resources/Mosquito-Borne-Illness
• Travis County: http://www.austintexas.gov/department/vector-control 
• National (Centers for Disease Control--will not be as timely as local reports, but offers national insights) https://www.cdc.gov/westnile/statsmaps/preliminarymapsdata2018/index.html 

Asian tiger mosquito a focus of last week's training

Keith Haas demonstrates use of a handheld ULV applicator
for treating adult mosquitoes hiding in dense vegetation.

For which important urban insect pest did 70% of pest control companies get more calls last year? For which pest are 88% of pest management professionals (PMPs) confident that control options are better than they were five years ago?  For what pest do nearly 2/3 of companies have callback rates of 4% or less?

According to a 2017 report by MGK^® Co., the repeated answer is "mosquitoes". It appears that pest control customers increasingly want to fight pesky mosquitoes in their backyards, and are willing to pay for it. 

Ultimately, this increased interest in mosquitoes is what brought 15 interested PMPs to the "Practical Mosquito Control" course last week at IPM Experience House. And, as students learned, the driving force for this demand may just be the tiny Asian tiger mosquito (ATM), Aedes albopictus, and its slightly less common cousin the yellow fever mosquito, Aedes aegypti.

A fast and opportunistic biter, tiger mosquitoes are relatively new pests, having arrived from Japan only about 30 years ago. When people complain that, "the mosquitoes are terrible this time of year", chances are they're talking about the day-flying ATM. But ironically, despite it's irritating bite, ATM is not currently a public health threat in most areas.

"The one good thing about ATM", said Scott Sawlis, county entomologist for Dallas County Health and Human Services, "is that it reminds people that they need to wear repellent, and thereby protect themselves from the more dangerous disease-carrying species."  In the Dallas area that would be Culex quinquefasciatus, the stealthier, nighttime-flying, southern house mosquito.  Even though folks don't tend to notice the house mosquito as much, it's the one to carry West Nile virus, our most serious mosquito-borne disease. 

Sawlis and fellow instructors (myself and Dr. Sonja Swiger with Texas A&M AgriLife, and Keith Haas, with Central Life Sciences), spent the day explaining to class attendees about the need for mosquito control, and some of the differences between the target species.  At the end of the day we got to practice what we learned in class by conducting an outdoor inspection and spending some workout time on microscopes looking at these tiniest of pests at a bug eye level. 

During our inspection we discovered mosquitoes breeding (naturally) just a few feet from where class took place.  Afterwards, students got to see fresh-caught mosquito eggs and watch mosquito larvae wriggle through murky breeding media.  Haas demonstrated the ability of a ULV generator to go through and around landscape vegetation, and Sawlis demonstrated proper use of a dipper when trying to determine whether mosquitoes might be breeding in a water source.

Although ATM may be one of the best things to happen to the pest control business in the past few years, it does have a darker side. The ATM is very difficult to control from city spray trucks and even from the air.  And it remains ready to transmit the viruses for Zika and dengue fever, should these diseases arrive in our area like Zika did last summer in Miami, FL and Brownsville, TX.  

One of the most effective tools, our class learned, for fighting tiger mosquitoes is the PMP. While county and city mosquito control staff must patrol streets with sprayers that treat city-blocks at a time (a technique that works well for the house mosquito), only the PMP walks backyards, identifies and treats ground-level breeding sites, and precisely targets sprays to ATM resting sites. This puts the pest control technician in an important role to reduce the most frequent mosquito bites, and to fight Zika and other Aedes-borne illnesses, should they arise here.

If you missed last week's class, and would like to learn more about control of ATM and its biting cousins, several regional training classes will be offered over the next few months.  Stay tuned here for more information.  

Gleanings from ICE 2016

After an unintentional break in blogging due to a month of travel, I'm finally caught up enough to sit down with my notes and remember what it was all about.

If you can imagine thousands of entomologists swarming a convention center like fire ants on Cheetos, that's what it was like at the 25th International Congress of Entomology (ICE) held in Orlando, FL.  Held every three years, and rotating to a different nation every time, the ICE is the largest gathering of professional insect experts in the world--and this one may have been the biggest ever.  This year there were over 6,600 registrants from 102 countries, giving 5,396 presentations.

This was my first ICE, and it was overwhelming. It seemed like I spent half my week just sorting through the program to know which sessions and posters I should attend.  So probably like everyone who attends the ICE, I came away feeling like I had a unique, though very limited, perspective on the meeting.

One of the more enjoyable aspects of the Congress was meeting insect geeks from around the world. Some were bench scientists (who work in the laboratory), others worked in the field (including one enthusiastic fellow I met from Germany who brought his own dung on a field trip to trap Florida dung beetles--and it worked!).  There were first time visitors to the U.S., and many young and enthusiastic students. I met scientists from Finland, Vietnam, Australia, Kenya, and Iraq. But in the research sessions we were all just entomologists, despite different dress, language or customs.

So here are some highlights of my notes from the many hours of sitting in sessions and looking at PowerPoint slides:

• German cockroach resistance to baits was the subject of a paper by NC State University researcher Jules Silverman. When comparing a susceptible German cockroach strain versus a field strain from Puerto Rico, his team found resistance to fipronil (15-20X), indoxacarb (15,000X) and even hydramethynon (350X). This was the first time hydramethylnon physiological resistance (as opposed to avoidance) has been found. Even with this resistance, in the lab they still saw complete control of cockroaches with gel baits.  But control was not as good in field trials where cockroaches had access to other foods.  My take home message was that we must be careful in our use of cockroach baits, and use them in combination with sanitation, sprays and other control tactics if we want to preserve them for coming years.

• Paula Stigler Granados from the UT School of Public Health reported on the status of Chagas disease in the U.S.  Dr. Granados leads a task force studying the best way to protect human health from this important, disease transmitted by kissing bugs.  Doctors tend to downplay the risk of Chagas disease and rarely test for the disease.  Blood banks only test for Chagas if a person is a first time donor; hence some are concerned about the possibility of our U.S. blood supply becoming contaminated with the Chagas disease parasite. It's estimated that as many as 98-99% of cases in the U.S. remain undiagnosed.
        Educational awareness among doctors and patients will be a focus of the Texas Chagas task force, along with better screening, diagnosis and treatment.  Chagas is a chronic and ultimately fatal disease.  In previous years it was considered untreatable; but with a new drug therapy it now can be treated in earlier stages. Getting the drug to people who need it is still a challenge, however.
• In related papers Dr. Gabe Hamer from Texas A&M reported on the results of a citizen science effort to study kissing bugs. From 2013 to 2015, they collected 2,812 bugs from 98 different Texas counties. The most common species detected was Triatoma gerstaeckeri, with 63% of those collected infected with the Chagas disease pathogen.  Another study by Rodion Gorchakov from the Baylor College of Medicine in Houston showed that humans are the most common host for kissing bugs collected by citizen scientists in Texas with human blood found in 66% of bugs.  So why not more Chagas disease in Texas and other parts of the U.S.?  The current theory is that gerstaeckeri and our other native kissing bug species are not very good at transmitting the disease during biting--something to be thankful for.
• A couple of the more interesting and fun talks I attended were on insects and Japanese art and culture.  Some of you may know Dr. Nan Yao Su, developer of the Sentricon system concept at the University of Florida.  Turns out he is interested in insect influences on Japanese culture.  
• Gunter Miller, from Hebrew University in Jerusalem, Israel, spoke on the process of developing effective attractive toxic sugar baits (ATSBs) for mosquito control.  Based on the fact that both male and female mosquitoes feed on natural sugar sources (like nectar, honeydew), ATSBs must be competitive with these natural sources, so the process of developing these baits is more complicated than just mixing sugar with a pesticide and spraying it on plants.  Their lab developed a "mosquito sangria" mixture (includes beer and Sangria) that will remain attractive to mosquitoes for more than a month after spraying.  Their technology is being used in the Terminix All Clear Mosquito Bait Spray.  This approach to mosquito control has attracted a lot of attention because of its potential to control some Aedes mosquitoes (vectors of Zika, and the most common daytime biters), and because of its need for less insecticide that might be harmful to beneficial insects.  
• Joel Coats from Iowa State University has been studying alternatives to PBO, the most commonly used synergist for pyrethrins and other pyrethroid insecticides.  He found that many of the plant extracts he tested synergized permethrin as well or better than PBO, and many worked faster than PBO.  Apparently PBO was developed early as a standard synergist for the industry, and few people have taken the time to look at alternatives over the past 50 years. Having an organic synergist could be a real market boost to pyrethrins sprays, most of which cannot be sold as organic because of the synthetic PBO needed to make it effective.
• According to MacKenzie Kjeldgaard of Texas A&M University, who analyzed ant gut contents with sophisticated DNA techniques, the fire ant's top food source was crickets, but also included springtails, caterpillars, flies and spiders.  
• Freder Medina introduced a new BASF termiticide injection system using Termidor H.E.  The new application system uses 4000 psi pressure to inject the insecticide into the ground, eliminating the need for drenching.  The system will come with a base unit and mobile app to communicate with BASF.  You should be hearing more about this in 2017.
• Last, I had a pleasant surprise in the commercial exhibits when I discovered a new book just published by Stephen Doggett, University of Sydney, Australia.  Stephen is a well known bed bug researcher, but had the genius to put out a handy photographic guide to bed bug infestations for, well, just about anyone.  It has dozens of excellent photos, tells where and how to spot bed bugs and what to do if you find bed bugs in your home. This should be a useful resource to share with pest control customers, and as a training tool for employees.  Self published, and not widely available, but you can get it at BioQuip books for about $7.

Of course there was much much more information at ICE this year, some of which I may incorporate in future posts.  But it's Saturday and time to get on to other activities. I hope some of this has been interesting and helpful.

Webinar on mosquito control Monday

Drs. Grayson Brown (top) and
Nicky Gallagher are featured
speakers at next week's Webinar.

Just a short post today about a webinar on mosquito control for PMPs on Monday, July 25.  It's sponsored by PCT magazine and will be held at 1 pm CDT (that's Texas time).  Free signup is available here.  Speakers are Drs. Nicky Gallagher with Syngenta, and Grayson Brown with the University of Kentucky, both excellent speakers and knowledgable in mosquito control technology.

My reason for plugging this particular webinar is its timeliness, in combination with the surprising growth of the mosquito control portion of the pest control industry over the past couple of years.  I was shocked to learn at this spring's National Conference on Urban Entomology that mosquitoes are now big player Orkin's #1 annual residential service offering.  And I was amazed to hear that Arrow Exterminating's mosquito annual revenue went from $39,000 in 2004 to $6.5 million in 2015,with mosquito control customers among their most loyal customers.

So if you service residential accounts and are not yet providing mosquito control services, you might want to check out this offering. All you need is a computer and connection to the Internet. What could be an easier way to grow your business?

West Nile virus risk high in north Texas

Residual insecticides applied via backpack mist blower
sprayer can provide 3-4 weeks of mosquito control  during
times of peak mosquito activity.

July and August are typically the months of highest risk from west Nile virus, and true to form the past few weeks Dallas and Tarrant counties have seen a major increase in not only mosquitoes themselves, but infections within the mosquitoes.

After the major outbreak of WNV in 2012 in north Texas, some health officials made a decision to use something called the Vector Index (VI) as a form of threshold to ramp up mosquito control efforts.  Based on when human cases started to soar in 2012, and on suggestion from the CDC, a VI of 0.5 was determined to be a good threshold to consider going from ground based spray efforts to aerial spraying.

Two weeks ago the VI exceeded that threshold in both Dallas and Tarrant counties.  Both counties publish very interesting reports, available to the public, that include graphs to show  the latest mosquito counts and VI numbers.  To see the trends in Dallas and Fort Worth areas, check out the graphs below.  In the first graph, the Vector Index is the heavy red line.  Last week it exceeded the 0.50 threshold, although there was a drop this week. Note also the numbers of mosquitoes this summer (red bars) compared to average trap catches in 2012 (for the past four weeks, higher than 2012 averages shown by the blue bars). In Tarrant County (Fort Worth and surrounding communities) the VI (green line with triangle points) was likewise up last week, over 0.60 (new data is not yet published).  Note that the most recent 1-2 data points are preliminary estimates and may change as all the data is calculated.

These data are why there is discussion about aerial spraying this week.  In 2012 the number of human cases of WNV in Dallas county reached almost 400, and there were 19 deaths attributed to WNV. Serious business. Last week DCHHS issued a health advisory to the public, and this week the Dallas County commissioners voted to authorize the health department to prepare for possible aerial spray operations should conditions warrant.  

Where does all this leave the PMP who provides residential mosquito control service?  Municipal mosquito spraying actually complements, rather than replaces, mosquito control work on the ground done by professionals.  Aerial spraying generally provides better coverage of the tree canopy where WNV carrying mosquitoes (Culex quinquefasciatus in north Texas) live and mostly feed. Municipal truck mounted ULV sprays provide some control of lower level mosquitoes (Aedes mosquitoes that potentially transmit Zika and dengue fever, among other diseases), but they typically do not provide high level control in backyards or areas protected from spray coverage.  In that sense, the best control of Aedes mosquitoes is accomplished by your boots on the ground, looking for and treating or eliminating mosquito breeding sites, treating doorways, and treating shrubbery and other mosquito resting sites that are difficult to reach from the street.

As you and your technicians visit mosquito control customers this summer, keep in mind that you carry some of the most effective tools in the war against mosquitoes.  This summer, with Zika fears and WNV threats, what you do is more important than ever.

New Zika Resources for the Public

Hiring a professional is one way that the public
can help reduce mosquito biting risk around the home.

I was asked a few weeks ago if the collective "we" (meaning the whole state of Texas) were going to be ready for Zika.  My answer was a cautious, "I think so".  If we're not, it at least it won't be for lack of trying.

Zika is a much different disease than West Nile virus. It has different vectors, mosquitoes that prefer to feed on humans over any other animal (unlike WNV mosquitoes, which mostly feed on birds).  It is also very difficult to detect in wild mosquito populations.  The mosquitoes are more difficult to control with spray trucks, so responding to local cases is going to depend more on public cooperation.

Unlike WNV, Zika is virtually undetectable in the blood supply, as there is no approved way to screen newly donated blood to see whether it has the Zika virus in it. If Zika does make it into the country, it will also potentially affects more people.  Any family with members of childbearing age will need to be on high alert. The CDC recently released its response plan for Zika.  It's assumptions are sobering:

• Travel-associated and sexually-transmitted cases will continue to occur and are likely to increase. (we just don't know how much!)
• Local transmission (spread) of Zika virus in US territories and affiliated Pacific Island countries is ongoing.
• Neither vaccines nor proven clinical treatments are expected to be available to treat or prevent Zika virus infections before local transmission begins nationwide.
• The ability for mosquito control efforts to reduce infection risks may be limited, as has been the case with similar viruses, such as dengue and chikungunya.

The entomology department, and especially my colleague Extension entomologist Dr. Sonja Swiger, has been busy in recent weeks trying to figure out how to best arm everyone with the best information on how to prepare for the "Summer of Zika".

As part of the effort, some new fact sheets from Texas A&M AgriLife Extension are now available to answer some of the more common Zika questions. These may be useful for your customers who are worried about mosquitoes and how to protect themselves.  The DIY fact sheet talks about the different consumer-oriented treatment options, including hiring a professional.

• Zika Precautions for Women (ENTO-053) is a new publication outlining the most important steps women can take to protect themselves and their unborn children from Zika.  Protecting women is the top priority for public health agencies this summer.
• What Texans Need to Know About Zika Virus (ENTO-052) General information about Zika, what causes it, whether you should be worried, and how to stop it. (Spanish Version)
• Mosquitoes and the Diseases they Transmit (ENTO-040) Provides an overview of all important disease carrying mosquitoes in Texas.  Revised in 2016. (Spanish Version)
• Buzz Off (ENTO-055) A short reminder of the 4-Ds, the four ways to avoid mosquito bites.  A quick safety reminder for yourself and employees.
• DIY Backyard Mosquito Control (ENTO-054)  An overview of all the mosquito control options available to consumers, including hiring a professional.  Advantages and disadvantages of each option are listed, including what we know and don't know about the many products out there.  (Spoiler alert: don't buy bug zappers for mosquito control--they don't kill many mosquitoes)

Highlights of NCUE

Albuquerque, NM was a beautiful (and tasty)
location for this year's NCUE meeting.

One of the first professional meetings I attended as a newly minted PhD entomologist was the National Conference of Urban Entomology. Held that year in College Park, Maryland, the meeting was a revelation.  Finally, I thought to myself, a gathering of people who understand what I do for a living--like a Cheers bar for entomologists!

We've all been to parties and been asked what we do for a living. Answer that you're "an entomologist who specializes in structural insect pests", and if you're lucky you'll get a wan smile. Rarely does anyone get it. Not so at the National Conference of Urban Entomology. The NCUE is a gathering of very friendly, slightly nerdy, science-oriented people who love to talk about urban insects and pest control.  No one in this group needs bother with common names when discussing Periplaneta americana, or Coptotermes formosanus. Talks like "Gut bacteria mediate aggregation in the German cockroach" are guaranteed to draw a crowd.

This year's NCUE meeting was held in Albuquerque, NM, and it did not disappoint.  Besides a short, but packed agenda of buggy stuff, Albuquerque was a wonderful place to meet.  Not a whiff of Breaking Bad drug labs, but lots of clear skies, mountain and desert views, and great New Mexican cuisine. (Oh, and The Donald was even in town one night!)

To give you an idea about what all of us bug scientists talked about in the sessions and hallways this week, here are some of my notes to self:

• Pest exclusion was the dominant topic for one session and was revisited throughout the meeting.  Imagine if homes and offices could be designed to keep pests out, or at least make them uncomfortable.  Dr. Jody Gangloff-Kaufman from the New York State IPM Program talked about two relatively new working groups dedicated to promoting better building standards to resist pests.  They call their project SCOPE (Scientific Coalition of Pest Exclusion), and the two groups focus on residential and commercial buildings, respectively.  The group has been meeting for approximately 2 years and has about 120 members.  Goals are to assemble a database of literature that supports pest exclusion (PE) concepts, and to provide checklists for builders and architects to promote better PE. A bit of controversy arose when a session speaker suggested that perhaps the typical pest control business model would not willingly embrace pest-resistant buildings. A PMP participant objected saying that offering pest proofing was an important part of their business model and how their company remained competitive.
• Dr. Chris Geiger, with the City of San Francisco, spoke about how IPM and PE principles have influenced the LEED (Leadership in Energy and Environmental Design) program. LEED remains one of the most influential and successful certification programs ever, contributing $80.6 billion to GDP between 2011-2014 and changing the way architects design modern buildings. Dr. Geiger noted that 59% of LEED-for-existing-buildings applications take advantage of points for having an IPM program in place.
       Although LEED recognizes the importance of IPM to environmentally sound construction and maintenance of buildings, it has not provided strong leadership on pest exclusion. Consequently, in 2013 Geiger led a group to produce a guidance document for architects and builders to provide specific examples of how to make buildings more pest resistant.  These guidelines are being put to work in some major public housing renovations in San Francisco, and have been offered to builders as a standard to reference when trying to achieve IPM points in LEED projects.
       Dr. Geiger hopes to update these guidelines this year, and is actively seeking experts in pest control, engineering, entomology, and architecture to be a part of the process.  If you are interested in joining his group, go to this web form to add yourself to the list of participants.
• Dr. Tim Husen with Rollins Corporation suggested that PMPs needing fast access to a listing of low toxicity products acceptable to LEED certifiers can use a mobile phone app called PestSmart, available through the Pesticide Research Institute. I found and downloaded this free app quickly on the App Store for my iPhone.  The listing is based on criteria used by the City of San Francisco in their (now extinct) Tier III list of low toxicity pesticides.  This famed list is no longer supported or updated by the City of SF, but is still sometimes referenced by architects, especially under the now dated, V3 (2009) LEED credits.  Keep in mind that the PestSmart app provides an assessment of likely toxicity, but does not take into account risk of exposure, an important component of hazard (toxicity X exposure = hazard).  
• Famed "rodentologist," Dr. Bobby Corrigan, also spoke on rat exclusion, and provided a case history from the National Park Service's African Burial Ground Monument.  A highly sensitive, historically significant site in New York City, the property was heavily rodent infested prior to Corrigan's consultation.  Xcluder Geo Mesh was installed under sod at the site, and burrows were gassed with dry ice (2 lbs per burrow system) to successfully rid the property of these "diabolically clever" pests, as Corrigan described them. Though initially more expensive, Corrigan believes the use of CO2 and advanced mesh barriers like this could be very useful for eradicating rodents from sensitive locations.
• Not surprisingly, mosquitoes were a hot topic of discussion this year. PMPs are beginning to shift their company business models to include mosquito control. Orkin's Dr. Ron Harrison noted that mosquitoes are his company's number 1 annual service offering. Rick Bell, with Arrow Exterminating, reported that his company's mosquito revenue has gone from $39,000 in 2004 to $6.5 million in 2015, all with little reliance on automated backyard mosquito misting systems.  He noted that Arrow's mosquito control customers are among their most loyal, with a 92% annual retention rate. 
• Dr. Joe Barile of Bayer Environmental Science cautioned the industry about how mosquito control is marketed. He recommended use of the term "nuisance abatement" rather than any language that implied disease elimination or protection from mosquito borne disease.
• Dr. Grayson Brown from the University of Kentucky summarized some of the latest promising technologies for residential mosquito control. He reported that the Innovative Vector Control Consortium (IVCC), a group founded over 10 years ago to seek solutions to mosquito borne disease, is currently evaluating 9 new classes of active ingredients for vector control. If even a few of these insecticides prove safe and effective, it could revolutionize adult mosquito control. He also noted that essential oils are also receiving more study as insecticides, repellents and excitatory agents to enhance the effectiveness of other products.
• Although it appears that most pest control companies rely largely on barrier sprays as a core of their mosquito control programs, pollinator and beneficial insect concerns are an issue. Consequently, there is much interest in alternatives to backyard sprays for mosquito control. Among the promising alternatives, according to Brown, are autocidal gravid oviposition (AGO) traps.  These are artificial breeding sites for Aedes mosquitoes which trap, kill, contaminate or sterilize any female mosquito lured in to lay eggs.  In one study in Puerto Rico, 3-4 large AGO sticky traps per yard were sufficient to reduce Aedes mosquito populations 53-70% and prevented mosquito outbreaks following rain in 81% of homes. 
• Pyriproxyfen, the insect growth regulator in Archer® and Nygard® insecticides, is also being tested as an active ingredient in some autocidal traps.  Research suggests that besides killing their mosquito offspring before they emerge from treated water or cups, pyriproxyfen residues in these traps transfer via the mosquito herself to other breeding sites through a process called auto-dissemination. This is one of the coolest and most selective mosquito controls I've heard of.  If proven in the field, a PMP or homeowner, could put a few gravid traps out in the yard for minimal cost and get season long mosquito suppression with no risk to bees, butterflies or other beneficial insects.  In combination with sprays and other control methods, it might be possible to achieve a high level of control and reclaim mosquito infested backyards with minimal harm to good bugs. Currently few lethal ovitraps are commercially available; but watch for new products to enter the market soon.
• No gathering of urban entomologists would be complete without a few papers on bed bugs. Though the number of bed bug papers was down this year, those presented were oriented towards the practical.  Three papers came from Virginia Tech.  Dr. Dini Miller presented on bed bug vacuums. She found that all the battery powered vacuums she tested (several Black and Decker, and Dyson models) were surprisingly effective at removing adults, nymphs, exuviae and eggs. Besides offering a cleaner and more allergen free environment, it is notable that vacuums remove the exuvia (cast skins) of bed bugs.  This is important for control, she noted, as cast skins may be used by bed bug nymphs as a refuge from sprays.  She also recommended using disposable, knee high, nylon stockings over the mouth of your vacuum (which she colorfully called "condoms for your vacuum") to isolate your catches and reduce the risk of bringing bed bugs back to the office.
• Katlyn Amos, graduate student at VT, tested two multi-action insecticides against pyrethroid resistant bed bugs.  Both Tandem and Crossfire, a new product from MGK, performed well against these resistant bugs. 
• Molly Stedfast reported on mattress encasements for bed bugs.  One of her most important findings was that not all bed bug encasements were bite-proof. After stretching encasement fabric over the mouths of glass jars filled with bed bugs, and applying the fabric-covered mouths to the arms and legs of volunteers, many of the bed bugs were able to successfully feed. But as Stedfast noted, bite resistance is not an issue for box springs.  Nor may it be that critical for bed mattresses either.  Bed bug mouthparts are only about 1 mm long, so once covered with a mattress protector and sheet, the average sleeper should be well protected from any bed bugs trapped in a tight encasement.  Tight zippers and rip resistance are probably more important features when selecting an encasement. 
• In the category of really-interesting-science-that-may-not-have-an-immediate-application, Dr. Rachel Adams, University of California-Berkeley, talked about the microbial diversity of homes.  The ability of science now to take DNA swabs and identify 40 microbes from one's forehead has rapidly progressed from my college microbiology class where "cutting edge" meant plating out and isolating a few microbe colonies on Petri dishes. This new technology means we can now isolate hundreds or thousands of fungi and bacterial DNA from the average home. The challenge we have today is understanding what these microbes are doing.  Are they reproducing, or just there because they floated in from outdoors?  And what are their human health impacts, if any? We know that microbes can positively or negatively affect our health, allergies and possibly ability to ward off disease.  One example Dr. Adams gave was the so-called 'farm effect', where children who grow up exposed to bacteria associated with cows and manure have asthma rates as much as 4X lower than urban-raised children. Insects may play a role in delivery of some of these microbes, good or bad, into homes.
• Finally,  Dr. Coby Schal, one of the most interesting and creative urban entomology researchers in the country today, spoke about the gut bacteria in German cockroaches (Blatella germanica to us entomologists!). His research has shown that it may be bacteria that are responsible for much of cockroach aggregation behavior.  Cockroaches with their full gut bacterial complement grew up faster, reproduced faster, found mates faster, and were more efficient foragers compared to cockroaches without their gut microbes.  In addition, cockroaches were more attracted to the poop of other cockroaches with buggy guts, suggesting that these microbes might hold the key to developing a better cockroach attractant for trapping and control purposes. And you might be surprised how much cockroach feces humans are exposed to. A colony of 1,000 German cockroaches (a moderate infestation in some restaurants and apartments) produces an estimated 5 grams of feces per night, or nearly 2 Kg (4 lbs) of feces a year. These same feces contain 7.5 million units of Bla-g antigens, which can cause allergies or asthma in humans in amounts as little as 8 units.

Now you know what urban entomologists talk about when they get together. The subject matter may be boring, humorous or even distasteful to the average person; but be thankful that someone is interested in this stuff.  As for me, I'm glad there's at least one place where everyone knows my name. Cheers!

Elimination of tree holes for mosquito breeding

Tree holes near ground level are especially
attractive to the Aedes mosquitoes that may
spread Zika virus.

It seems you never know what interesting places and topics pest control will lead you. This week's rabbit trail for me was a discussion on how best to "fill tree holes" that are a common mosquito breeding site.

With the heightened interest in mosquito control and Zika virus this summer, tree holes are a significant problem. When a limb dies back or fails on a tree, the result is often a pocket in the tree that is capable of holding water. It turns out that such water-filled tree holes are perfect breeding sites for some mosquitoes, including Aedes albopictus and Aedes aegypti, the two potential Zika-carrying mosquitoes.

The standard mosquito control recommendation is to fill these holes to prevent their use for breeding. But how do we best eliminate such holes without hurting the tree?  Here are some practical suggestions on filling tree holes gleaned from colleagues and other reputable resources:

• Filling tree holes with concrete, gravel or sand is a no no. Gravel and sand may help hold water in the tree and promote decay.  Gravel and concrete pose a real safety hazard for arborists or tree owners when the tree eventually has to be cut down--and not good for the chain saws either.  Concrete also adds weight to the tree, and does not flex or bend, causing internal friction and damage to the tree over time.  
• Drilling drain holes to keep water from accumulating is no longer generally recommended, as it may open the tree up to further damage to health tissue, and infection. 
• If a tree hole does not hold water it may be providing wildlife benefits, providing a home for birds or squirrels(!).  On the other hand, tree holes may provide a nesting site for roof rats. 
• Not all tree cavities need to be filled.  However if a tree hole is retaining water or providing a breeding site for unwanted animals, expanding foam may be a good solution. This tool has been largely embraced by the tree care industry because it is lightweight and easy to carry into a tree and is safe for chainsaws.  It also excludes water and will flex and bend with the tree.  Some argue that foam is bad because water often finds it way in anyway and foam retards evaporation, but from a mosquito control perspective the benefits of sealing water-retaining holes probably outweigh the risks.
• As when using expanding foam indoors in a home, don't overfill a hole. Use a foam with a lower expansion ratio, and inject the foam slowly.  Because foams can be unsightly where they emerge from a cavity, you might want to consider a black tinted foam like Pur-black and/or consider smoothing off excessive foam overflow after drying.
• If rats or mice are an issue, using screen or or other pest control excluder materials in the filling may prevent their chewing their way back into the tree.
• It is not necessary to clean out decay from the cavity before filling.  And "tree paint" dressings are no longer recommended by arborists for fresh wounds on a tree.

Thanks to colleagues on the Ornaent Listserve for their interesting and enlightening comments on this question this week.  

BTW, since I've done it here today, referral to a commercial product or website is for informational purposes only and does not imply endorsement by me or by the Texas A&M AgriLife Extension Service.

New interest in mosquitoes

A simple bucket with leaves and compost becomes a
mosquito breeding site (see inset) after a rain. Photo
by M. Merchant in his own backyard (oops).

After last summer's West Nile virus epidemic in north Texas there is a heightened awareness of mosquitoes and mosquito issues around the state.

Every pest management professional, especially anyone involved with residential pest control, should think of mosquitoes as an opportunity to provide another valuable customer pest control service.

In my experience, few people imagine that they might be the culprit when it comes to breeding  mosquitoes.  Most folks believe that mosquitoes come from someone else's property--especially the creek across the street, or the neighbor's fish pond.

While this might be true, especially in the case of an abandoned pool or marshy area, we are often our own worst enemy. Most creeks, ponds and lakes are not major sources of disease-carrying mosquitoes.  Any body of water with fish, or with running water that is not stagnant, is not likely to be an important breeding site for the worst mosquito species--most of which are "container breeders". Rather, small containers or human structures that collect dust and debris along with water that sits for more than a couple of weeks, are the most likely source for our worst disease transmitting mosquitoes like the urban-dwelling Aedes and Culex species.

A few years ago, Dallas County did an evaluation on the properties of citizens who reported severe  mosquito problems in their backyards.  They found that 25% of citizens who complained about mosquitoes were  breeding mosquitoes in containers found in their own yards.

Green pools are common in neighborhoods with
foreclosed homes, and should be drained or
treated. Photo by M. Merchant

As a PMP you approach every property with trained eyes to see pests and to see conditions that are conducive to pest infestation. This skill can serve you well when inspecting a backyard for mosquitoes, and provide value-added to any pest control visit.  Here are some of the common problem areas to be alert for in residential yards:

• Water- and leaf-filled bird baths.  Bird baths should be emptied or cleaned weekly to minimize risk of mosquito breeding.  
• Gutters that fail to drain properly.  This can be difficult to see, but your extension mirror can help. Check gutters, especially after a rain, to make sure they are draining properly.  Leaves and dirt that build up in gutters provide the organic matter, all they need is water to make a mosquito breeding spot.
• Tires. Rubber automobile tires, it seems, are designed to hold water.  They are one of the worst sources of mosquito breeding in some areas.
• Buckets, plant pots and wheelbarrows without drain holes. These items should be inverted or hung to ensure that water is not held.
• Landscape and gutter drain lines that catch and hold water.  Poor installation of underground drain pipes allow water to stand.  Mosquitoes are adept at finding their way in and out of underground holes that we may not notice.  All underground drain lines should be fitted with a pop-up drain emitter that opens only when water is flowing.
• Water catch basins/septic tanks.  Catch basins in French drains and municipal storm sewers are designed to keep debris from clogging drain pipes.  But these same boxes can catch and hold water for extended times. Flush out catchment basins or apply a larvicide like Bacillus thuringiensis or methoprene.  Poorly closed or maintained septic systems can provide many breeding sites for Culex mosquitoes.
• Uncapped steel fence posts are often overlooked, but may hold water for long times after a heavy rain. Point out fence posts without covers and explain how any container that holds water can breed mosquitoes.
• Plastic or canvas covers on boats or trailers.  Tarps or plastic sheets used to cover vehicles or boats can easily hold water for a week or more.  Boat covers should be pulled taught to force water to drain.
• Rain barrels and cisterns. With most areas in Texas water is increasingly precious. Drought and water restrictions have encouraged many homeowners to install cisterns and rain barrels to capture and store rain water. While most commercial rain storage systems come with drains to keep mosquitoes out, screening on intakes and overflow plumbing can become damaged, and needs regular inspection.  
• Unmaintained swimming pools.  So called, "green pools" are unchlorinated pools that can become breeding sites for large numbers of mosquitoes.  If you notice such a pool and the homeowner is absent or unwilling to respond to complaints, these sites should be reported to the local health department as a public health threat.

Let's all do our part to keep our communities safer and mosquito free. Let your customers know when they have a dangerous situation.  Chances are that they will thank you for it.  For more information on mosquitoes in backyards, see the Mosquito Safari website.  

Legislative Note

Last week the Texas Senate gave thumbs up (28-3 vote) on a measure (SB 186) introduced by Sen. John Carona (R-Dallas) that would give municipal health officials authority to enter empty or abandoned properties to treat mosquito breeding sites that pose a public health nuisance. It can be difficult for health authorities to gain access to such properties without a search warrant.  This bill would allow a "public official, agent or employee charged with the enforcement of... laws" to enter the premises at a reasonable time to inspect or treat the nuisance stagnant water.

David Oefinger, with the Texas Pest Management Association, feels that chance for passage of the bill in the House is pretty good given the lack of opposition in the Senate.

What can schools do about mosquito control?

In case you haven't heard, mosquitoes have been big news in Texas lately. This summer has turned into the worst summer on record for West Nile virus (WNV) in Texas, and both Dallas and Houston have resorted to aerial attacks to attempt to stem the tide of the mosquito and the virus.

Now with a new school year starting up, many school districts are asking themselves, "What should we be doing?" Parents will be concerned about their children waiting at bus stops and participating in band and athletics practice.  And let's not forget about Friday Night Lights, and weekly football games.  What responsibility do schools have to take part in community wide mosquito control?  And if you work for a school district, what will you tell parents when they ask what the district is doing to keep their kids safe from West Nile virus?

Source Reduction
Perhaps the most important single thing a school district can do is make sure that school grounds are not contributing to local mosquito problems. It's especially important to check water catchment basins, storm drains, low areas, and equipment storage yards, athletic and playground equipment for places where water might be caught and held. If you do pest control in a school district, expand your vision at this time of year to look for and report potential mosquito breeding sites.

If a suspected breeding site is found, report it to your local health department, or if possible, drain the water or treat with it. Effective mosquito treatments include Bacillus thuringiensis (Bt) dunks or methoprene (Altosid®) granules or briquets.  Both of these are Green category insecticides.

Treating Mosquito Resting Sites 
Mosquitoes are primarily active in the evening and morning.  During the day, adult mosquitoes typically rest in vegetation or other shaded sites. We can use this information to reduce mosquito numbers. Treatment of mosquito resting sites can dramatically reduce bites and biting rates in the immediate area of treatment.

If you know of areas of vegetation, or shaded doorways where mosquitoes are a problem, consider treating such sites with a residual pyrethroid spray. Pyrethroid insecticides like deltamethrin, cyfluthrin, bifenthrin, and lambda-cyhalothrin (Yellow category) can provide up to six weeks control on vegetation or building surfaces. These products can be applied via hand-held pump sprayer, backpack mist blower, or power sprayer to doorways and trees, shrubs and ornamental grass around buildings and entryways.

Such sprays are probably not necessary on most campuses, but in sites with heavy shade and vegetation, and populations of biting mosquitoes, such treatments may be warranted.  If you choose to treat sites like this, remember to post the school 48 hours in advance, and keep students and staff out of treated areas until sprays have thoroughly dried.

Low Volume Treatments

One of the five planes used to apply mosquito
sprays over Dallas County this month. (Photo
courtesy of Dallas Morning News and Tom
Fox/Staff Photographer)

When most people think about mosquito control they think about trucks or aircraft applying a fog or mist. The treatments used by such government agencies are called ultra-low volume (ULV) sprays.  The very tiny particle sizes used in such applications allow better penetration into dense foliage, and generally mean quick dispersal and short life of spray residues.

Most school districts will not engage in ULV sprays, though some cities or mosquito districts may offer the district an option to be included in community-wide spray actions. If ULV insecticides are to be used for campuses or sporting venues, remember to follow posting and notification requirements. Yellow category justifications must generally be filed, because most ULV treatments use Yellow category products like resmethrin or permethrin.  Synergized pyrethrin applications may be considered Green, unless the synergizing additive in the spray concentrate (generally piperonil butoxide) is greater than 5% .

The effect on mosquitoes from ULV-applied sprays is generally short-lived (few hours to a day), so they should be used only on special occasions, such as an hour or more before a sporting event. Wind and weather also have an important influence on the effectiveness of ULV sprays, so be sure to measure and record wind speed prior to application and follow label restrictions carefully.

If your campus has been sprayed as part of a community-wide aerial spray campaign, no special precautions should be necessary.  However some districts have been making a point to let parents know that school play equipment has been washed after spraying.

Education and Awareness
Ironically for schools, one of the most overlooked components of an IPM program is education. Mosquito season provides an excellent opportunity to get mosquito control information out to the community, as well as raise awareness of your district's IPM program.

One of the most important messages that a school can send is the importance of wearing insect repellent when working or playing outdoors. Consider notifying parents and students advising them to wear a good repellent to school, or at evening sporting events.

Many districts have had questions about whether they can allow students to use repellents on school grounds. Personal use of repellents is not prohibited or addressed by state school IPM regulations. Therefore it is up to each district to decide whether students and staff can bring and use repellents at school.  Options include allowing students to bring repellents to a school nurse, and having the nurse apply if needed. Another option might be to allow only cream or non-spray repellent formulations, especially for band and athletic departments in middle and high schools.  The time to decide on the appropriate policy, however, is now, before students return to campus.  For more information on insect repellents, see the excellent repellent guide put out by the National Pesticide Information Center.

As a public service, consider assisting the Texas Department of State Health Services and other local health authorities get the message out about mosquito control.  There are many useful educational materials and websites (see below) that parents should be aware of. School districts can play a useful role in getting mosquito awareness information out to our communities. Consider linking this information in your school district’s website.

Some quick facts about mosquitoes and West Nile virus: 

• The southern house mosquito, Culex quinquefasciatus, is the primary carrier of WNV in most of Texas (different species carry the virus in other parts of the country). This mosquito is a container breeder.  It prefers to breed in small containers or puddles of standing water. 
• Water must stand for 10-14 days to be a problem for mosquito breeding.  It doesn't have to be a lot of water, but this is approximately how long it takes for mosquitoes to complete their life cycle at 85-90 degrees F.  
• Remember stagnant, polluted (stinky) water is the water that Southern house mosquitoes love.  Water where fish are present, such as a pond or permanent stream is not usually a big source of mosquitoes. 
• Not all people are equally attractive to mosquitoes. Body chemistry differs from person to person and some of us smell more attractive to mosquitoes than others.  Don't assume that because you aren't noticing bites that mosquitoes are not active.
• Remember the 4 D’s 
•  DUSK/DAWN- Stay indoors at Dusk/Dawn. This is the time of day that mosquitoes are most active. 
• DEET-Use insect repellents that contain Deet when going outside, especially at times closer to dawn or dusk when mosquitoes are most active. 
• DRAIN - Remove all areas of standing water. Examples are pet dishes, birdbaths, and water dishes under potted plants. Repair faulty French drains. Remove debris from rain gutters. Mosquitoes will breed in this debris since it is normally damp under the debris. Remove all piles of dead leaf material from under trees and shrubs. This also is a breeding site. 
•  DRESS- Avoid being bitten by mosquitoes by wearing light colored long sleeved shirts and long pants when going outside. 

Additional Resources

• Check out the eXtension school IPM action plan for mosquitoes.  If you don't have a plan for mosquito control in your IPM notebook, this may be just for you.
• Need a poster, flyer, or other information to hand out to teachers, parents or students? including a sample letter you can send home to parents? Check out this link.
• The Department of State Health Services website on school resources
• Frequently Asked Questions about aerial spraying for mosquitoes can answer many concerns parents (and customers) have about community-wide mosquito spraying
• Mosquito Safari is an Extension website with general information about mosquito identification, biology and control, including an interactive tour of common mosquito breeding sites. 
• Four new videos on how to mosquito-proof your home

Thanks to Janet Hurley and the Texas School IPM program in assembling much of the information for this post.