Catching the new drift on pyrethroids

For years agricultural pesticide applicators have been required to measure and record wind and weather at the time of spray applications. Wind matters in agricultural applications because of the potential for pesticide drift--the movement of pesticides from their intended target to undesirable sites such as other farm fields, homes, schools and natural areas. Weather matters because excessive rainfall can result in poor adhesion of sprays to plant or soil surfaces and pesticide-contaminated runoff--another form of drift.

In structural pest control, drift has always been an issue also, but on a much smaller scale.  For structural pest control indoor applicators, drift can occur in the form of splashback during both spot and crack and crevice liquid insecticide applications indoors. It can also occur with dust applications (I still remember my dismay, as a young and inexperienced applicator, when a compressor fan kicked on, blowing the pyrethrins dust I had just applied to a cockroach-infested motor back in my face). Outdoor applications can "drift" under windy conditions, or when rain washes residues from the application site to streams or lakes.  In fact, pesticide runoff is the reason that EPA has moved recently to change labeling requirements on new pyrethroid insecticide labels.

The new pyrethroid label standards by the US EPA are now out, and should be on every pest control service manager's required reading list. Unfortunately, they are not that easy to find, nor understand. I recently had the opportunity to sit in on the webinar update on these new standards by Jim Fredericks of the National Pest Management Association. NPMA has been working hard to keep up with these new standards and Jim did a nice job summarizing the new use directions you will be seeing shortly on all pyrethroid pesticide labels.

Digital handheld wind meters are relatively inexpensive,
accurate and can have powerful options such as wind
direction, temperature and relative humidity.

Two weather-related issues appear in these new requirements. First, for pre-construction termiticide applications only [see update in the May 1 comment below], the new labels will say,“Do not make on-grade applications when sustained wind speeds are above 10 mph (at application site) at nozzle end height.”  This means that anyone doing pre-construction termiticide treatments will have to have some method of measuring wind speed [as far as I can tell wind speed measurement is not required for general pest spray applications around residences and businesses].  There are at least three ways I know to estimate wind speed accurately:

• Purchase and use a digital wind meter, like the one in the accompanying image.  Today's units range in price from $20 to $200, depending on features. They can include barometric pressure, relative humidity, temperature, altitude, etc.
• Get a old-fashioned Dwyer handheld windmeter for about $25. This tough and dependable unit (doesn't need batteries) works on air pressure to elevate a small plastic ball, providing a simple wind speed measurement.
• Go to an online website that provides windspeed data for your location, such as  http://www.intellicast.com/National/Wind/WINDcast.aspx. The problem is that the wind speed at your local airport may not be the same as at the account where your applications are made.

Second, the new labels will prohibit any pyrethroid spray, granular or dust applications made when it's raining. In areas where rain is frequent, or constant at certain times of year, this may be inconvenient (and who's to say when it's really raining?), but the intent is clear.  When it's raining, insecticides will not adhere well to surfaces and are prone to running off the target site into storm drains or streams.

Finally, anyone doing outdoor applications (especially termite pre-treatments) should consider adding spaces on your business' service forms for weather data, like wind speed and precipitation. If you're an honest applicator who goes by the book, this sort of information can only help you if called upon to defend an application.  An on-site reading taken from a handheld wind unit always trumps NOAA area weather data, and could save your rear in a legal case.