Monday, August 27, 2012

Summer flu often spells West Nile Virus

Dr. Robert Haley, Chief Epidemiologist of the UT Southwestern Medical Center in Dallas, recently wrote a short and easily readable summary of the West Nile virus situation for the Journal of the American Medical Association (JAMA).  Click here to read a free copy of the article.

Based on his medical observations over several years, Dr. Haley concludes that "diagnosis of WNF should be suspected in anyone with unexplained fever from late June through September, the season when other causes of fever are least common. Fever with disorientation, stiff neck, or neurologic deficits suggests WNND."

It's estimated that since its discovery in the U.S. in 1999, over 30,000 Americans have contracted either West Nile fever (WNF) or the most serious form of the disease, West Nile neuroinvasive disease (WNND). While even I may have been tempted a few years ago to dismiss this as an "old person's disease" (older persons with underlying health problems are most likely to die from the virus), at over 50 myself I now fall into the susceptible age group. And I don't feel that old.

It would be a mistake to underestimate this disease. It can even develop in younger people, as a 14 year-old Dallas girl discovered this summer, although this is not common.  Even the milder form of the disease can be debilitating for extended periods of time, with an average recovery time of 60 days in one study.

For PMPs working in residential environments, especially, it's important to take WNV seriously. Higher concentrations of DEET, picaridin and IR-3535 remain the best repellents for outdoor workers due to their longer residual and highly effective repellency for WNV mosquitoes.  For more information and assistance in choosing the right insect repellent for you and your employees, check out the highly useful repellent calculator developed by the National Pesticide Information Center.

Thursday, August 23, 2012

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

Tuesday, August 21, 2012

The Ugly American

American cockroach,
Periplaneta americana
If one were to poll pest control customers about what they thought was the most disgusting insect, there's a good chance the American cockroach would come out at top. First of all it's large and scary, it's very fast and, where it proliferates, it stinks. Add to this that the American cockroach is one of the few cockroaches that readily flies, and you've got a disgusting pest.

Since few people want to admit to having giant cockroaches in their homes, alternative names are often given to the American cockroach, waterbug and palmettobug being the two most common. One of our largest cockroaches (reaching lengths of just over two inches), they often look much larger to a surprised customer. They are often described as three or four inches long.

American cockroaches, while much longer lived and slower to reproduce than the more common German cockroach, can become quite prolific in the right environment.  While an American cockroach female only produces about 12 eggs per ootheca (egg case), compared to the German cockroach's 36, she lives much longer and produces more oothecae and potential offspring over her lifetime (an average 360 offspring vs the German cockroach's 320 offspring).  Left undisturbed, American cockroaches can build up impressive populations, as anyone who has opened an infested sewer manhole cover can attest.

Odors from the droppings and the insects
themselves can be noticeable in heavy
infestations of American cockroaches. Note
the stains from cockroach droppings on
these boxes in an infrequently used
storage area. Photo by Fudd Graham.
I guess one of the things that's always impressed me about the American cockroach is its ability to survive in places with little food.  They are relatively common in urban sewer and storm drain systems, as well as steam tunnels and basements and storage areas of institutional buildings like schools, hospitals, prisons and factories. These cockroaches are often living on the edge, nutrition-wise, making do with feeding on glues and starches associated with boxes and papers. They are opportunistic feeders and while they prefer fermenting foods, they will feed on dog food in the lab and will readily feed on various cockroach baits.

My colleague Dr. Fudd Graham, from Auburn University, was recently inspecting a courthouse with a chronic American cockroach infestation. Following his nose, his inspection led him to a storage room that hadn't been opened for over 18 months. The two tubes of  Advion cockroach bait Fudd applied were gone the next morning along with the cardboard on which the bait was applied. 

Typical of many infested areas of buildings, this room had a floor drain that, due to lack of use, was dry.  Dry floor drains are one of the most common entry points for American cockroaches to enter commercial buildings from sewage systems.  Many people, even building maintenance professionals, are unaware of the importance of periodically pouring a gallon or two of water into floor drains to fill the p-trap that is designed to block sewer gases and insects and other pests from entering buildings.  A dry p-trap allows cockroaches ready access to a utility room or food storage area in a building. Besides filling the p-trap, some companies have developed clever membrane devices that open for water flow, but close between use.  Trapguard and Sureseal are two commercial products and, while they can be expensive to install, provide a long term fix for gas and pest infiltration into storage and utility areas. 
The half-inch-long ensign wasp
(Evaniidae) is a sign of American
cockroach presence in a building.

Its important to remember that controlling American cockroaches has other benefits.  Eliminating American cockroaches helps reduce the potential food supply of rodents in a building. I'll guess that most PMPs have seen the disembodied wings and legs of American cockroaches left on sticky traps. This is often evidence of mice or rats, which are fond of snacking on live cockroaches plucked from sticky cards.  In addition, ensign wasps are a common parasite of American and smoky brown cockroach oothecae, and are often seen flying around buildings that have an American cockroach infestation.  While harmless themselves to people, the presence of these interesting insects is a sign of cockroach presence in a building.

Wednesday, August 1, 2012

Pyrethroid labeling confusion

New FMC videos explain pyrethroid label changes.
In April I posted information on the new pyrethroid label changes being required by the U.S. Environmental Protection Agency.  While the information in my April 17th post was correct, I later (May 1) posted a comment based on additional information I received from the EPA.  In that follow-up comment I said that, according to EPA, that ALL outdoor pyrethroid applications (not just preconstruction treatments as stated in the article) would not be permitted when windspeed was over 10 mph.  The problem is that I was misinformed by my EPA source.

I shared EPA's May 1 label interpretation with Dr. Jim Fredricks at the National Pest Management Association.  He and his legislative colleague, Bob Rosenberg, followed up with EPA on this information.  In an email dated 19 June 2012, Rosenberg received a response from EPA stating that their original "response (the one I received) was not correct... the 10 mph wind restriction applies only to products labeled for preconstruction termiticide applications." [my emphasis]

To those of you who read my comment, I apologize for passing on the wrong information.  Thanks to NPMA for following up and ensuring that all of us get the correct information about pyrethroid label changes and what they mean. BTW, this is a great example of the kind of service tha the NPMA provides its membership as it looks out for the interest of the industry.

I have since removed the incorrect information from the April post's comments; however pyrethroid labels may include advisory language recommending application should be made during "calm weather when rain is not predicted for 24 hours".  This may be more difficult to gauge and document than the 10 mph requirement.

As usual, if in doubt, read the label.  If it's a pyrethroid label, be extra careful over the next few months to check every pesticide container.  During this transition period some containers will have labels that have the new language, and others will not.  While technicians are OK if they use a product with the old language, it would be a good idea to train and require all your employees to start following the tighter restrictions now.

FMC Professional Products has produced some nice new videos explaining the new pyrethroid labels. Check them out at the FMC YouTube Channel.