IPM Thresholds: More than meets the eye

I've heard several pest management professionals say that they felt thresholds were not practical for their business. "We have a zero tolerance for pests," they typically say, "so thresholds just don't work for us." Health department standards are often cited as a justification for a zero threshold, as many health departments have no tolerance for cockroaches in a food handling establishment.

Developed originally for agriculture, pest thresholds originally meant the level of pest presence on a crop where the damage caused by the pest equaled the cost of treatment (usually the cost of a pesticide application). This concept works well in situations where the cost of a single pest is relatively easily determined. It's much more difficult to establish thresholds where pests are simply a nuisance or where the exact health cost of an individual pest is difficult to define.

The problem of assessing pest damage in indoor environments is especially challenging. What is the cost to a restaurant of a single cockroach in a kitchen? Contrary to the myth that a single cockroach is sufficient to shut down a kitchen, health inspectors, in Texas at least, are charged to "[control pests] to minimize their presence within the physical facility and its contents, and on the contiguous land or property under the control of the permit holder..." Nevertheless, we all know that there are levels of pests that are clearly unacceptable.

Most people would agree that a single cockroach, or one mouse, entering a facility from a recently delivered box of food does not necessarily constitute an "infestation". And one or two cockroaches on a sticky card would likely justify a much different (and less costly) response than, say, 30 cockroaches found on several sticky cards. This is where thresholds can help both the pest control technician and the food establishment manager.

I believe the most useful kind of threshold for these settings is what I call the multiple response threshold, where thresholds are used to guide the appropriate response to escalating pest densities. A good technician understands this concept intuitively, whether he or she realizes it or not.

This week I helped conduct a class on IPM for school maintenance personnel. As part of the class we conducted a pest inspection of a school kitchen. The technician who serviced the school told me he had recently found two cockroaches in a particular area of the kitchen we were inspecting. I asked him what he did, and he said that he conducted a thorough inspection of the area and found no other signs of cockroaches. He did not apply a pesticide, but planned to keep a close eye on this area in the next few visits. When asked what he would have done had he found more cockroaches, he answered that he would have increased sanitation, brought in a vacuum and perhaps placed out some cockroach bait stations.

This is, in my opinion, the proper use of the IPM threshold concept for buildings.

But if a good technician knows this intuitively, then why is it necessary to have written thresholds? There are several reasons I can think of for written thresholds, especially for institutional accounts such schools, restaurants or hospitals: (1) Not all technicians are equally experienced, or understand what to do when they encounter different levels of pest problem; (2) not all institutions or businesses have the same tolerances for pests. If they have been previously reviewed and approved by the customer, written thresholds provide a way to ensure that the technician is familiar with the expectations of each account; (3) technicians rarely keep the same accounts for extended periods of time, so having written thresholds is an excellent training tool and way to standardize service among technicians; (4) the process of developing thresholds is a useful exercise in thinking through your IPM service strategy; and (5) thresholds can save time and expense, especially for institutions where pest control service is based on a work order system. It can be expensive to send technicians out on trivial pest control service calls, when more important calls await. In this case, thresholds can help a manager decide which work order requests deserve immediate response, and which are given lower priority.

If your company does not include written thresholds as part of its commercial IPM program, it may be time to reconsider. Besides being a good idea, having thoughtful and reasonable thresholds might just distinguish your company from competitors who also claim to be doing IPM.

Fire ant baiting season winds down

If you and your company use baits as part of your fire ant control programs in Texas, or elsewhere in the south, now's the time to use up your bait for the year.

Fire ant baits are wonderful tools for controlling fire ants. They are low in toxicity to users, customers, pets, and even most other non-target ants. They are one of the most economical methods to control fire ants, and one of the most effective, consistently providing 90% or more control.

So what's not to like about baits? One of the few disadvantages of baits is that they are not equally effective throughout the year. Throughout the temperate areas of the southern U.S. fire ants stop searching for food (foraging) when soil temperatures drop below about 60 degrees F. If the ants stop foraging they will not pick up baits like Amdro Pro, Advion and Extinquish Plus. For this reason, baits should not be part of your winter fire ant program unless you work in south Texas or south Florida.

Venturing outside my office this afternoon, the soil temperature at 2 cm (a little less than 1 inch, the best measuring depth) was a comfortable 81 degrees F. This is well within the optimal soil temperatures for foraging of 72 and 97 degrees, so right now is still great weather for using fire ant baits--at least in the Dallas area. If you are unsure whether baits can still be used in your area, take soil temperatures at 1 inch during the morning and afternoon. If the average is between 72 and 97 degrees, you can probably still use baits.

Fire ant baits are best used when fresh, so any containers that have been opened within the past few months should be used soon. Fire ant baits have a relatively short shelf life once opened. Even unopened bait should be used within two years of manufacture. Because of this, buying large quantities of bait (perhaps because it's at a good price) is not necessarily a wise idea unless you are certain you can use the bait up during the season of purchase.

As temperatures drop over the next month or two, it will be best to limit your fire ant treatments to individual mounds, using labeled contact or residual insecticides. Winter is also a good time to apply broadcast treatments with granular fipronil (e.g., Top Choice), since it may take up to two months to see full control with this product during the fire ant season. Though more expensive and, ostensibly, not as "low-impact" as baits, granular fipronil provides good control for up to a year in most locations. It is also a good treatment to apply around the perimeters of structures to prevent colonies from settling close to a building where they might seek shelter during the winter.

Train your technicians to be generous when treating fire ant mounds with liquid insecticide mixtures. Research shows that best control with liquids is obtained when 1-2 gallons of liquid is used per mound. Avoid the use of granular or dust treatments of mounds in sensitive environments like schools or parks, since these products may remain on the soil surface for several days or weeks after application.

For more information about when and how to use fire ant baits, check out the fire ant website section on broadcast baits.

No such thing as an "ant"!

I'm convinced that training employees to document what they do is one of the most important, yet overlooked, aspects of technician training in pest control. If you're doing your work well, you want your work documented in the service tickets and logs and other paperwork you leave behind.

One of the best indicators of a well-trained technician is careful and descriptive recording of pest problems encountered during a service visit. One of the signs of a careless or poorly trained technician is sloppy notes.

I first noticed this a few years ago when serving as an expert in lawsuits involving fire ant stinging accidents in nursing homes. As part of the discovery process, it was my job to go through service tickets and note when and where fire ants had been noted by the pest control company.

To my dismay, I found that there was no way to distinguish what the technicians had been doing during their many visits to the locations I researched. Notations on the service logs and service tickets would typically read "treated for ants". Wait a minute. There's no such thing as just an 'ant'. What kind of ants? Pharaoh ants would require applying one of a few effective protein-based baits designed for pharaoh ants. Odorous house ants might require a sugar-based bait. For fire ants an outdoor treatment and inspection would be necessary, along with use of broadcast fire ant baits or outdoor mound treatments. Without good documentation, one has to assume that the technician didn't really know (or care) what he was doing.

We encounter the same problem when reviewing service tickets left behind in public schools. The past few years my colleague Janet Hurley and I have visited a number of public schools in various states to audit their IPM programs. In the process we've seen many service tickets left behind by pest control technicians documenting pesticide applications for "ants", "roaches", "flies", etc. As anyone who has worked in the industry can tell you, identifying a potential pest to ordinal level doesn't really tell you much. There's a world of difference, for example, between finding a dozen German cockroach nymphs and an American cockroach in a sticky card in a previously cockroach-free commercial kitchen. Think potentially dozens of service hours and repeated callbacks if the problem is not caught early. There's no such thing as just a "roach".

Flies are another great example of why identification skills and documentation are so important. Fly control is based on finding and eliminating the site where the larval stages of the flies are breeding. House flies in a kitchen? Check the outdoor dumpster and the back door. Fruit flies typically involve spilled syrups, rotten fruits or vegetables. Phorid flies may indicate a sewer problem. The customer may not know the difference, but the technician should. And the technician should communicate with the customer, a process that starts with the service ticket. There's no such thing a just a "fly".

Documenting pesticide use is another issue that I will undoubtedly revisit on another day. But today, just remember that when it comes to quality pest control, "there's no such thing as an 'ant'!"

Nematodes for pest control?

A question came up today among an online extension fire ant community concerning the use of nematodes to control fire ants. Occasionally I hear from homeowners asking whether nematodes will work as a viable alternative to pesticides for flea, fire ant or white grub control in yards. I thought a little bit of background into nematodes (nemas, for short) might be of interest.

Nematodes make up their own phylum of organisms, the Nematoda, with over 80,000 species, according to Wikipedia. Though many species are plant feeders, a number of kinds are entomophagic, or insect eating and have potential for helping us control pests.

Unfortunately, putting a potentially beneficial organism to work for us is rarely as simple as we would hope. For this reason, if nematode control is ever to be widely used, it will have to be professionals that make it work.

Take grub control for instance. Control of white grubs in turfgrass is an area where nematodes can be successful. To learn more, Dr. Parwender Grewal, of Ohio State University provides useful recommendations for selecting an using nematodes against white grubs and other turf-infesting insects. Because nemas are living organisms, however, control procedures can be complicated. For this reason, I don't think we'll be seeing many do-it-yourselfers embracing use of nemas for yard insect control.

Professionals are much better equipped to provide this kind of service because of its very complexity. Pest management companies have access to microscopes to check viability of the nematodes prior to application. Also, professionals are able to develop the necessary skills and experience, and can establish and follow protocols that are necessary to get consistent control.

Fungus gnats are another pest that can be successfully control with nematodes. In a study by Harris, Oetting and Gardner in 1995, the nematode species Steinernema feltiae was just as effective as the insecticide diazinon in controlling fungus gnats. This approach is especially valuable in interior plantscapes where chemical use is undesirable and plants cannot be easily moved. Similar to using an insecticide, soil media is drenched with nema-containing solutions to prevent fungus gnat reproduction.

Unfortunately, fire ants have never been easily controlled with nematodes, due to their habits of grooming and ability to detect and evacuate sites where nematode populations are high. Dr. Robert Dunn at the University of Florida has developed a short fact sheet on this subject. According to Dr. Sanford Porter at the University of Florida, other more promising species of nematodes for fire ant control are being investigated. But right now the fire ants seem to be winning the nematode war.

What about other pests? Termites, like fire ants, are not easily controlled with biological control agents like nemas because of the difficulty in delivering predators and parasites to underground termite colonies. Also, flea control with nematodes is also not very promising at present. This approach has never been convincingly demonstrated in the field, as Dr. Dunn discusses in another fact sheet on flea control.

Playing without Pesticides?

In case you've not heard, there's a movement afoot to ban pesticides as part of a green approach to community improvement. Pesticide bans are most common in schools and parks, but are even being proposed (most famously in Toronto, Ontario) for whole cities. A recent news story from New Jersey tells of a school in Mansfield, NJ that has taken to posting "Pesticide Free" signs near the playgrounds to advertise the school's policy of not using pesticides (at least around playgrounds).


Such actions, in my opinion, are misguided and teach kids the wrong lessons. Those of you who love kids and the environment, like I do, please hear me out before you click the "close" button on your browsers.


Let's ask ourselves, what message do pesticide bans really convey? Let me propose a few.

• All pesticides are bad for the environment. This message ignores the diversity of pesticide products, all of which are different in their modes of action and degrees of toxicity. A pesticide is, by definition, something that manages pests, not something that is dangerous for the environment. The environmental impacts of today's pesticides are significantly different than the products that Rachel Carson warned us about in the early 1960s. Few of today's pesticides, for one example, have the potential to accumulate in the food chain.


• All pesticides are unhealthy for kids and the rest of us. Not true. The older, nerve-toxin targeted pesticides have undoubtedly contributed to this misconception; but there are lots of pesticides that pose very low risks to humans and non-targeted organisms.Over the past twenty years or so, especially, pesticide toxicity and persistence has decreased dramatically.


• You can't trust science-based regulatory agencies to keep unsafe pesticides out of our communities. While I'm not ready to go to bat for all our federal regulatory agencies, few people fully appreciate the vetting process that U.S. pesticides go through before making it to market. Suffice it to say here that pesticides go through much more thorough and expensive safety testing than most other consumer-destined products.


• We don't really need pesticides. This message denies the value that pesticides have historically provided in keeping food costs down (for the poor as well as the rest of our society), saving human lives by keeping disease-carrying pests at bay, improving safety and appearance of athletic fields (ask your kid's high school coach about this one), and maintaining healthy and comfortable environments for all of us (care to share your sleeping space with bed bugs anyone?).

Leonard Douglen, Executive Director of the New Jersey Pest Management Association, made a good point in a recent editorial when he observed, "When one considers the many insect pests that can attack children, from ticks that can cause Lyme disease to mosquitoes that transmit West Nile Fever, cockroaches that can spread a variety of diseases, as well as stinging insects, the need for professional pest control becomes self-evident."

One final observation. Pesticide bans may be more palatable to consumers, and seem more acheivable, in cooler, northern communities where outdoor pest problems are less common and less severe. In the southern states the warm season is longer, weeds grow faster, and insect and plant disease pressure is significantly greater than, say, Toronto. Under these conditions, pest management is more essential to maintaining safe and attractive landscapes. Try taking the average Texan's bag of fire ant bait away from him or her, and you'll quickly understand what I mean.

Legislators should be careful lest they think that pesticide bans are the way to go. I propose a more thoughtful and nuanced approach. It may not be as fashionable or simple a message as "Pesticide Free", but requiring use of integrated pest management, and making sure that pesticide applicators are well trained in the safe and judicious use of pesticides will, in the long run, be best for us and our environment.