Wednesday, December 7, 2016

Attic Safety

If you do pest control, few work sites can match the extremes of what you find in attics. Work in attics can be hot (or cold), difficult and dangerous if you’re not at the top of your game. Yet inspecting and servicing attics can be a critical aspect of pest control, especially for residential customers.  So in the spirit of keeping safe during the holidays, here are a few tips I've gathered for working in attics.
Having a stable work platform and maintaining three points of
contact when moving are essential for attic safety. (Photo by
JoistMate™) 

Scheduling. In Texas, heat may be the biggest safety challenge of all in attics. If possible, it's best to schedule any summer attic work for the morning. Afternoon attic temperatures in Texas in the summer can range from 120 to 180 degrees F– dangerously high. Most pest control inspections in attics will be relatively short, but if you have to spend any significant time in an attic, get an early start and make sure you have plenty of water and/or electrolyte drink handy.

Clothing. Proper clothing is needed to protect you from Fiberglas insulation, nails, hard objects and possibly bites and stings.  Long-sleeved shirt tucked into pants, safety glasses and bump hat are pretty important. Thick soled shoes or boots to protect against nails are highly recommended. And take it from someone with more than his fair share of bumped heads, if you don’t have a bump hat--any kind of cap or hat is better than none.

Safety Equipment.  Perhaps the most important attic safety gear is a respirator. A disposable NIOSH rated N-95 respirator (retains 95% of 0.3 micron-sized particles) is the minimal protection you need from short exposures to Fiberglas dust in attics. Cheap surgical masks are not sufficient here. If you suspect rodents are present, especially in rural homes where deer mice could be present, more sophisticated protection is needed. The CDC publishes recommendations for risk reduction when working in environments where hantavirus is a risk. For any PMP who removes deer mice from traps, or work closely with rodents, CDC recommends a half-face, tight-seal, respirator with N100 filter. If you have facial hair, like I do, or if you do not medically qualify to use a negative seal filter, you may need a (positive pressure) PAPR (powered air-purifying respirator), equipped with N-100 filters.  Expensive!

A fit-tested, half-face respirator with N-100 filters is the
minimum protection you should wear when working around
rodent droppings or other potential biohazards.
If you'll be handling dead animals in an attic, insulation or other vertebrate-pest contaminated materials, rubber, latex, vinyl or nitrile gloves are essential.  You will also need a sprayer or spray bottle to spray infested insulation or dead rodents with a 10% bleach solution, and two plastic bags to hold the dead animals.

Tools. Carry any loose tools you need in a tool bag that you can drag with you. Always set your tools aside in the tool bag rather than on a rafter and risk losing them among insulation. Bring a corded work light or backup flashlight with you. This will be important if you drop your primary flashlight, or if your primary light's battery fails.

A digital camera may be very useful for documenting what you find in the attic.

Getting Around. If you must travel from stable flooring onto joist beams, follow the rock climber's rule and maintain three points of contact at all times. Move only one foot or hand at a time, keeping your other feet and hands on a secure joist or rafter. Joistmate™ (see picture) is one commercially available platform designed to provide a stable platform for working on joists.

Take the advice of a PMP friend who fell through a ceiling many years ago, "never step blindly into insulation assuming a joist or floor decking will be there. If you cannot see the decking, beams or joists, DON’T STEP THERE. And don’t assume that all joists are on 16 inch centers. Twenty-four inches is more common in newer homes." He also advises everyone to be wary of beams or joists that might be damaged by termites or rot. They may not hold your weight.

It's a good idea to disturb insulation as little as possible to avoid stirring up dirt, dust, fibers and mold. Even when wearing a respirator, you'll want to minimize tracking contaminates down from the attic on clothing.  And if you see old vermiculite insulation, which if breathed can cause cancer, leave it alone.

Be Ready for Surprises. You are in the attic for pest control purposes, so be ready for pests! Keep a sharp eye open for signs of bee hives or wasp nests, or other pests like rats, bats, squirrels or raccoons. The possibility of being startled by encountering a scurrying pest is another good reason to have at least three good hand-holds or secure footing at all times. Always think about your escape route in case you encounter a wild animal.

Vaccines. In this business keeping up with your tetanus shots is a good idea, especially in a location where a sharp nail can appear where you least expect it.  If it's been more than 7 years, you need a booster shot.  And if you work in an area with bats, or where you commonly encounter wild (possibly rabid) animals like skunks or foxes, consider a rabies vaccine.  It is MUCH cheaper to get the rabies vaccine before you need it, than getting it after being exposed to the bite of a rabid or potentially rabid animal (personal experience here again, story for another post).

Ladders.  Falls from ladders are a leading cause of occupational death nationwide. If you use a ladder to access an attic, make sure it is firmly set up (75 degree angle is best) and rated for your weight. Don't descend a ladder face forward. Maintain that three point of contact rule and don't reach for items when ascending or descending. It's also a good idea to place plastic under the attic ladder, or be prepared to vacuum any insulation or debris that falls from the attic into the house.

Considering all the potential hazards working in attics, you might ask, "why bother?" Certainly anyone who manages urban wildlife, or does rodent control, knows that attic service is an essential part of their work.  But termite inspectors and PMPs doing general household pest control also have plenty of reasons to venture into attics or onto roofs. Let's promise ourselves that when we do, we'll put safety first.

If you have any memorable experiences, or safety tips for working in attics, I'd like to hear about them. We're in the process at A&M of putting together an attic servicing and safety curriculum as part of the new IPM Experience House. Your input could be an important addition to our training class. Contact me via the email link under my complete profile at right.


Saturday, November 19, 2016

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.

Friday, August 5, 2016

Comparing dusts for bed bug control

For several years PMPs have known that dusts can be useful tools in the management of bed bugs, but a new paper in the Journal of Economic Entomology by Narinderpal Singh and colleagues at Rutgers University shows just how powerful they can be.

Singh et al. used four different lab assays and two strains of bed bugs to probe the efficacy of eight insecticide dusts.  Each assay showed a different aspect of how these dusts perform.  Together, I think, they do a pretty good job of evaluating how you can reasonably expect these products to perform in the real world.

Four experimental assays used to study the toxicity of
various dusts and predict their effectiveness in the field.
Clockwise from upper left (1) brief exposure assay, (2)
choice assay, (3) assay where CimeXa-treated bugs are
allowed to mingle with untreated bugs, and (4) continual
exposure assay with treated paper . (Singh et al. 2015,
J. Econ. Entomol.)
One of the problems with doing lab assays is that they can be highly unrealistic.  Sure, you can put an insect on a treated surface and watch them until they die (a continuous exposure assay).  Certainly this kind of assay can tell you whether there is potential for a product to work; but in a customer's home do your bed bugs have nothing better to do but sit on the insecticides you put out?  Probably not.

More often than not in the real world, insects run quickly across an insecticide barrier and then spend most of their time resting on untreated surfaces. Insecticide exposure may be only a matter of seconds. At other times, insects that move back to a treated harborage may be able to sense when they are on insecticide residues.  They may then choose to move to a clean spot that has not been sprayed or dusted (a sign of repellency).  Continuous exposure assays may overestimate the effectiveness of insecticide applications, especially when applications do not reach key harborage areas, or when residues are repellent to the pest.

On the flip side, insects may inadvertently pick up insecticide residue from a treated surface and carry that insecticide on their cuticle back to a harborage area. When this occurs they may transfer it via contact to other bed bugs clustered in the same harborage.  Failure to account for this in lab assays might end up underestimating the effectiveness of your treatment.  

Singh and colleagues tried to account for all of these possibilities in their research. One assay required the bugs to sit on treated paper for the length of the study.  A second assay had the bed bugs walk across a treated one-inch barrier.  And a third test gave the bugs the choice to visit and rest on either dust-treated or untreated surfaces.
Bed bug dusts included in the trial were Tempo, DeltaDust, Cynoff, Pyganic, EcoPCO D.X, Alpine, MotherEarth, and CimeXa. 

As you might expect, all products killed bed bugs when they sat continuously on the treated surfaces. After five days there was 100% mortality for all bed bugs in the treated dishes. When bed bugs were allowed to choose freely to rest on either treated and untreated surfaces, CimeXa and Tempo gave 80-95% control after one day; however after 10 days MotherEarth (diatomaceous earth) and Cynoff were close behind.  

The clear champion of the toughest test, the brief exposure test, was CimeXa Dust. CimeXa provided 95-100% mortality (at 1 and 10 days after exposure) to bed bugs crossing a one inch barrier of the dust.  Tempo was the next most effective product in the brief exposure trial, providing 40-60% mortality against the two bed bug strains. This ability to kill bed bugs with very short contact can be a game changer. It suggests that CimeXa may be capable of providing decent barrier protection on bed and furniture legs, in dressers or even along door thresholds (though unprotected deposits will likely be quickly rubbed or swept away). 

Singh and his team then went on to see whether CimeXa might also have the ability to transfer from exposed to unexposed bed bugs. It did. Clean bed bugs, that had not been previously exposed to CimeXa, when placed with CimeXa-treated bugs also had significantly higher (80-100%) mortality after 10 days compared to untreated controls.

Singh's work backs up previous work done by Mike Potter's lab in Kentucky.  Potter's group found that CimeXa was more effective than liquid Temprid residues against resistant bed bug strains in continuous exposure assays. He also found that as a stand alone treatment in infested apartments it provided rapid and marked control, superior to diatomaceous earth, and similar to that provided by the top liquid insecticide sprays. 

What these studies tell me is that insecticide dusts should definitely be part of your bed bug control program, especially in accounts with insecticide resistant bed bugs.  Silica aerogel, the active ingredient in CimeXa, performed better than the other commonly used desiccant (MotherEarth, i.e., diatomaceous earth), and even out performed the other pyrethroid dusts.  It should be noted, however, in settings where harborages can be fully dusted, these other products may still provide good control. And laboratory tests cannot fully duplicate what happens in the field--your real world accounts.

But my real reason to single out this study is that it provides a true low-risk option for bed bug control.  Because the mode of action of desiccant dusts is based on abrading the cuticle of the insect, and not on any mechanism that would potentially affect human health, it's a no-brainer to make these products a mainstay of your dust arsenal.  Used inside furniture, behind drawers and baseboards, in cracks and crevices of bed frames, these products make excellent, safe to use, treatments. Even if heat treatment is your tactic of choice, insecticide dusts can provide a long-term supplemental treatment to kill any bed bugs that might re-infest an apartment, hotel room or other bed room.

If dusts are not an important part of your chemical or heat treatment protocols, you may be missing out on a relatively economical, effective and safe option to improve your success rate against these adaptable and tough-to-kill pests.  


Monday, August 1, 2016

Zika the real deal for Texas PMP

More than 1600 cases of Zika have been reported in the U.S. so far, but until last week all of these had been in travelers--people who caught the virus somewhere else and brought it here.  As of last week, however, the picture is changing.  Last week four cases among people who had not traveled outside of their town were reported from north Miami in south Florida.  In an alarming development for Miamians this morning, 10 new locally acquired cases were reported today, likely signalling the first home grown epidemic of Zika infection in the U.S. All cases so far have been restricted to the north Miami neighborhood of Wynwood.

Jackie Thornton's Zika rash appeared about ten
days after he became infected.  It itched like
measles, he said.
Could this happen in Texas, or other states?  Absolutely.

When Jackie Thornton volunteered at his church to go on  a summer mission trip to the island of Dominica in the eastern Caribbean, the last thing on his mind was Zika virus.  Jackie is the owner of Alvin Pest Control in Alvin, TX, and long-time PMP.  "I was more worried about bed bugs," he admitted.

But when he arrived on Dominica (pronounced doe men NEE kah), someone mentioned that Zika and Chikungunya cases had been reported on the island.

Life in Dominica is a world away from a Texas suburban town like Alvin. Nighttime temperatures this time of year typically hover around 85 degrees F. Not so hot that air conditioning is a necessity, and besides few could afford such luxury.  The home where Jackie and his team slept was typical for the area.  Keeping cool at night depended on a nice breeze coming through one of the unscreened windows.

Knowing that Zika was around, and being an Associate Certified Entomologist, Jackie got interested in what was flying in his window.  Each night he would catch a few mosquitoes that looked more like house mosquitoes than the yellow fever mosquito, believed to be the primary Zika carrier.  Maybe things wouldn't be that bad after all.

But he got worried again about Zika about a week after arriving. "I developed a low grade headache that seemed to be behind my eyes," he said.  "It was worse when I woke up and lessened as the day progressed."  Eventually four others on his team also got sick, but not enough to keep any of them from working their shifts at vacation Bible school and helping repair homes damaged by Hurricane Erica.

After returning to Texas on July 24 the headaches persisted.  Two days later he woke up with joint pain in his hands, elbows, knees and feet, he said.  The next day, about a week and a half after the first headaches started, he went to the doctor for his joint pain.  On the way to the clinic, an itchy rash broke out "head to toe".  It was like having measles, he said.

Red itchy eyes was the only classic symptom of Zika that Jackie didn't have.  But he says he saw plenty of folks with red eyes while he was there.

Today, two and a half weeks after the first headache, he still itches, but the headache and joint pain is not as bad.  In typical PMP trouper fashion Jackie said he never felt like he had to be bedridden, but that it's been an "uncomfortable nuisance".  Indeed Jackie worked at his pest control company all last week, albeit while wearing long sleeves and lots of insect repellent to reduce the chance of starting his own Alvin, TX epidemic (an important community health precaution for any returning traveler, sick or not).

He now says, with a little bit of irony, "I may be the first U.S. PMP to come down with Zika."

I tell Jackie's story to remind us all that the risk from Zika virus is real... especially for anyone traveling to an area where Zika infections are active.

To see a map showing cities at highest risk for Zika this summer, click  http://www.cbsnews.com/news/zika-virus-mosquitoes-us-cities-most-at-risk/

To learn more about "Zika precautions for Women", see http://citybugs.tamu.edu/files/2016/06/Ento-053-Zika-Precautions-for-Women.pdf  and "What Texans Need to Know About Zika" see http://citybugs.tamu.edu/files/2016/06/ENTO-052-What-Texans-Need-to-Know-about-Zika.pdf




Tuesday, July 26, 2016

The OTHER clothes moths

This week I received reports of two insects that are sometimes confused with clothes moths or pantry pests. The brown house moth, Hofmannophila pseudospretella, is a common moth pest in the United Kingdom, but much less so in the U.S.  In a paper written in the 1950s, one researcher noted that it probably occurred in small numbers in every private home in Britain, and that few stores or warehouses in Britain were without at least a small population.  The brown house moth specimens I saw on a sticky card this week, however, were the first ones of this moth I've ever encountered in Texas.

Brown house moth on sticky card.  Head to tail, these  
small moths are between 4 and 7 mm long. 
The BHM could easily be mistaken for Indian meal moth based on size.  But wing patterns are different.  Wings are bronzy brown with dark flecks on the forewings.  It is a slow grower with about one generation per year, but capable of becoming abundant under the right conditions.  It appears to require high relative humidity of 80% or more, perhaps accounting for the fact that it is not so common in climate controlled homes here in the U.S.

The diet of BHM is varied, ranging from cereal products to wool and dead insects.  It is readily capable of developing in wheat germ, whole wheat, damaged beans, macaroni, fish meal.  When yeasts were present, it could also develop on feathers and flannel wool.

Woodroofe, a British entomologist who studied the moth over 60 years ago, felt that the importance of this moth in homes was more as a fabric pest than a pest of stored grains.  If this moth is found in a home the most likely source of infestation would likely be in a basement or garage with higher humidity.  Check for pet food, woolen clothing, furs or feathers being stored under damp conditions. Also look in light fixtures with dead insect accumulations, or old bird nests in chimneys or soffits. Sticky traps may be useful in catching some of the moths for identification. If the suspected site of infestation is in an inaccessible void, consider dusting the area with Cimexa or Tri-Die, or other dessicant dust. If given a chance, these little moths can become very abundant.

Household casebearer cases collected from a
home in east Texas.  Note the caterpillar head
emerging from the case on the far right, and the
flattened cases widest in the middle. Photo by
Randy Reeves.
Another interesting insect that I encounter more frequently in samples is the plaster bagworm or household casebearer, Phereoeca uterella.  A close cousin to the clothes moth, household casebearers live inside a spindle-shaped silken case.  University of Florida provides a nice article on this moth, which feeds largely on spider webs.  If that sounds like an odd thing to eat, remember that spider webs are a type of proteinaceous silk, and probably just as nourishing to a clothes moth as silk clothing made from silkworm silk.

Like the BHM, household casebearers thrive in higher humidity conditions.  The cases, like a silk purse, are usually flat in later life stages.  It is most likely to be confused with the casemaking clothes moth, a more frequently encountered pest; but the spindle shape, and flattened case are distinctive.  According to the Florida fact sheet these cases may be found "under spiderwebs, in bathrooms, bedrooms and garages... on wool rugs and wool carpets, hanging on curtains, or underneath buildings, hanging from subflooring, joists, sills and foundations; on the exterior of buildings in shaded places, under farm sheds, under lawn furniture, on stored farm machinery and on tree trunks."  Besides spider silk, the caterpillars have been observed to feed on wool, human hair and dead insects.

I've not heard of any infestations severe enough to require insecticide use with household casebearer. In most cases they seem to be a curiosity more than anything; but a vacuum cleaner to get rid of spider webs would be a good idea to make sure that your casebearers don't decide to nosh on something a little more valuable in the home.

Friday, July 22, 2016

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?


Thursday, July 14, 2016

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.