Friday, May 27, 2016

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.
  • Also related to LEED, Dr. Tim Husen with Rollins Corporation noted some of the challenges posed by limiting what pesticides can be used in LEED certified buildings. LEED requires use of least toxic pesticides in buildings that are to receive an IPM credit. LEED allows use of the City of San Francisco's Tier III pesticide list as one way of ensuring compliance with this requirement (though the City of San Francisco points out that their list was not created for LEED and is designed for city use only).  Nevertheless, Husen argued that lists like Tier III must be regularly updated to be useful.  Also, that although such lists evaluate products on important criteria like toxicity and probability of carcinogenicity, such lists do not consider risk of exposure, which can be quite low for some products that might otherwise not qualify for the list (BTW, this appears to have been fixed in the latest v4 LEED standards). Failure to consider exposure risk in determining least-risk products eliminates many useful and low risk pesticides in LEED certified buildings (for example cockroach baits placed in inaccessible cracks and voids). PMPs needing fast access to a Tier III list for reference 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.
  • 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!

Saturday, May 7, 2016

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.

Monday, May 2, 2016

New resource for managing turfgrass pests

If your business has anything to do with keeping turf and lawn areas beautiful and healthy, you're going to want this new book just published by Texas A&M AgriLife Extension.   (120 pp., 52 tables) The Weed, Insect, and Disease Control in Turfgrass guide was written by Extension specialists Casey Reynolds, Matt Elmore, Young-Ki Jo, and Diane Silcox Reynolds. It's probably the best single reference to pesticides used in turf, at least in Texas.

Despite some who claim that we need to eliminate turf to save water and reduce pollution from fertilizers and pesticides; healthy turf is essential for our urban areas.  Turfgrass is vital to our parks and urban landscapes, athletic fields, and golf courses; it helps moderate temperatures in urban areas, it holds the soil, and provides a soft cushion for our lives. Unfortunately, southern turf is often challenged by numerous weeds, insect pests and disease.  But with proper selection and judicious use, pesticides can help turf do these jobs better with minimal impact on the environment.

Information in the Weed, Insect, and Disease Control in Turfgrass 2016 guide will help you select the herbicides, insecticides, and fungicides you need. But the guide is far more than a listing of  pesticides.  It includes information on pesticide modes of action, turfgrass tolerance, application rates. It also provides an annotated, pest by pest index of labeled pesticides.

Hard copies of this book are available through the AgriLife Bookstore for $20.  But the electronic version is available for free download here. Also, if you haven't seen the new and updated Aggie Turfgrass website, check it out.  It has excellent descriptions of the most important Texas turfgrasses, and management information for weeds and insects.  It also has links to past and upcoming events like turfgrass field days in Dallas or College Station.

Monday, April 18, 2016

Webinar on Emerald Ash Borer

Trunk injections made by professionals are
one of the most effective tactics for
protection of urban trees. Learn more about
EAB management options at Wednesday's
free seminar.
For anyone interested in learning the latest information about the exotic pest, emerald ash borer, there is a training opportunity later this week that might be just the ticket.  Dr. Dan Herms, professor and chair of the entomology department at Ohio State University, has been involved in EAB research nearly since its arrival.  He will be offering a one hour webinar this Wednesday at noon.

Dr. Herms will be talking about the implications of EAB for both natural and urban areas of the Southeast, the next major region this insect is expected to invade.  The EAB is now known to be within 40 miles of Texas, and may already be here.  Every ash tree in eastern Texas is at risk, and arborists, especially, will benefit from advanced training on this insect.

Here's the official announcement:
The emerald ash borer (Agrilus planipennis Fairmaire) is now found in 25 U.S. states and Canada in North America, and is rapidly expanding its range across the eastern United States. It has the ability to kill all species of ash trees (Fraxinus spp). 
Being prepared for EAB is important if this pest is to be contained. This webinar will review EAB identification, biology, ecology and management strategies, with particular emphasis on the southeastern U.S. EAB is now considered the most devastating wood pest in North America. 
Dr. Herms has been involved in EAB research and outreach since its discovery in Ohio in 2003, and is also a collaborator with other entomologists researching the pest. No pre-registration is necessary for this webinar. Click here for information on how to join the webinar on April 20, 12:00 CDT. 
Tree care companies, Extension specialists, Master Gardeners, urban foresters, Natural Resources Conservation Service specialists, tree boards, tree nurseries, municipal managers, nature conservancies, and anyone concerned about the future of this important tree species will find this a very useful and enlightening presentation.
Other websites with information about EAB:

Tuesday, April 5, 2016

Preparing techs and apprentices

Janet Hurley, our school IPM program specialist, just sent out this reminder that I thought would be good to pass on to Texas readers of this blog.  If you have a technician or apprentice who could benefit from a prep class, you should know about our Ag and Environmental Safety Department offerings. 
Our office has received a lot of questions recently regarding training to help employees get their pesticide applicator's license. Dr. Don Renchie and his team with the Department of Ag and Environmental Safety offers a variety of classes throughout the year for you to choose from. Below are just two of the several courses they offer. 
General Standards Training.    This training is designed to satisfy the Structural Pest Control Service’s requirements for certification of Commercial/Non-commercial and Technician licensing of pesticide applicators (8 hours of training). This is the general training, and not category training. While the Texas Department of Agriculture does not require training as a condition to be licensed, this class will help prepare the applicant for the TDA General examination.  
Please note: This class can be used to satisfy the 8 hour re-certification training requirement for technicians. 
Classes are from 8:00 a.m. to 5:00 p.m. with an hour lunch (lunch is not provided). Deadline for registration is one week prior to training date. Registration is $150.00 per person. The fee includes study manuals (General Standards - B-5073, and Structural Laws & Regs - B-6135). Register online at, or call (979) 845-2604.  
2016 Dates: 
  • Houston - 3033 Bear Creek Dr. 
    • May 25, 2016 
    • August 23, 2016 
    • November 17, 2016 
  • Austin - 2210 South FM 973 
    • July 13, 2016 
    • September 22, 2016   
  • Fort Worth (replaces the Dallas location) - 1100 Circle Drive 
    • February 2, 2016 
    • April 13, 2016 
    • July 27, 2016 
    • October 12, 2016 
  • Corpus Christi - State Hwy 44, West 
    • June 22, 2016 
  • Overton - 1710 FM 3053 North 
    • June 8, 2016 

Please contact the Structural Pest Control Service at (512) 305-8250 or (866) 918-4481 to register for the computer-based testing program for structural pesticide applicators. Applicants must be pre-qualified by TDA prior to registering to take examinations with PSI Services.  
For best test results, order your additional category manuals in advance. Please make separate payment if ordering additional manuals. To order manuals over the phone, call (979) 845-1099 or (979) 845-3849.  
Three Day Apprentice Training.  You can now provide your technician apprentices and other employees with an opportunity to receive 20 hours of in-depth, hands-on training relating to the 20 hours of “Classroom” training required by the Texas Structural Pest Control Service, effective September 1, 2000.  
This program will exceed the minimum 20 hours required to satisfy the apprenticeship classroom training as established by Section 7.133 (h) (1) of the Texas Structural Pest Control Act. In addition, untrained personnel from local and state governments, industry, and institutions (such as school districts) will benefit greatly from participation in this training program.  
Prepare your pest management personnel to be successful professionals, register today! Register online at key word 'apprentice' or call (979) 845-2604.  
Training will be conducted at Texas A&M University’s Riverside Training complex in Bryan, Texas. A map to the location will be provided upon registration. Cost is $350.00 and includes study materials (B-6135 Laws and Regulations, and Apprentice manual). Lunch will be served each day.  
For additional questions, please call (979)845-3849 or (979)845-1099 or visit the Ag & Environmental Safety website at  
2016 Dates: 
  • May 10-11, 2016 
  • August 9-11, 2016 
  • November 1-3, 2016

Monday, April 4, 2016

Another three years of Termidor Section 18 label

Pest management professionals on the front line of the battle with tawny crazy ant (TCA) (Nylanderia fulva) can breath a little easier.  Last Friday the U.S. EPA issued a Section 18 quarantine exemption to allow Termidor® SC to be applied as an extra wide treatment zone around homes and buildings in infested Texas counties.

The Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) is perhaps the most important law governing pesticide use and pest control in the U.S.  Section 3 of FIFRA has to do with registering insecticides, and establishes the process by which different pesticides usually get their label approval. This is why you may hear people refer to the standard label on a pesticide container as a "Section 3" label.

Sometimes states have a need for a new use, or pest, that is not allowed under a regular Section 3 label.  When that occurs, the state may request an amended label, called a Section 18 emergency, or Quarantine, exemption.  Section 18 of FIFRA authorizes EPA to allow an unregistered use of a pesticide for a limited time if EPA determines that an emergency pest condition exits. An emergency condition must be an urgent and non-routine situation where 1) no effective registered pesticides are available, 2) no feasible alternative control practices exist, and 3) the situation involves the introduction of a new pest, will present significant risks to human health or the environment, or will cause significant economic loss.

Dead tawny crazy ants pile up around a Termidor® treated
building perimeter.  Once enough dead ants accumulate, other
ants can cross the treatment zone on the bodies of their nest
mates (photo by Jason Meyers).
Several years ago BASF found that Termidor® SC Termiticide/Insecticide was highly effective at killing TCA, but did not always  effectively keep TCA out of buildings.  This happened because TCA numbers were so great in infested areas, that dead ants would pile up around the treated perimeter of buildings. As dead ants accumulated on the allowed one-foot out treatment zone, other ants would simply crawl over the zone on the dead bodies of their nest mates.  It became apparent that the standard one-foot-up and one-foot-out perimeter treatments allowed under the Termidor® Section 3 labels were inadequate to protect homes and businesses from invasion by this ant.

The latest Section 18 granted to the Texas Department of Agriculture (TDA) allowed applications to be made as a 10-feet-out (on sod) by 3-foot-up perimeter treated zone.  This last exemption ran out on November 1 2015, and anxious PMPs have been waiting for its renewal since.  This week's announcement will allow the 3-foot-up and 10-foot-out Termidor® SC use this year when ants become active again, according to Extension entomologist Dr. Paul Nester. Nester noted that the label restricts users to two applications per year per structure, at least 60 days apart.  Most people, he said, apply first in late June, when ants become troublesome, and then again in late August.

The Section 18 label restricts its exemption to infested Texas counties only:
For control of tawny crazy ant species associated with man-made structures in Texas within the counties of Bexar, Brazoria, Brazos, Cameron, Chambers, Comal, Fayette, Fort Bend, Galveston, Hardin, Harris, Hays, Hidalgo, Jefferson, Jim Hogg, Liberty, Matagorda, Montgomery, Nueces, Orange, Polk, San Augustine, Travis, Victoria, Walker, Wharton, Williamson, and to include additional counties where positive identification has been made (by Texas A&M entomologists).
The list will change as the number of infested counties goes up (and it will), so it's a good idea to check the current range map maintained at Texas A&M.

Though there are other fipronil-containing sprays, only Termidor®  SC has the expanded perimeter Section 18 treatment option.

According to Nester, most applicators use Termidor® or Taurus® treatments in combination with yard treatments of either dinotefuran, lambda-cyhalothrin (or other pyrethroid), or a fipronil granule.

This week's announcement came from Dale R. Scott, Director for Environmental and Biosecurity Programs at TDA.  He encourages anyone with questions to contact Kevin Haack (TDA Coordinator for Pesticide Evaluation and Registration) or Mike Kelly (TDA Coordinator for Structural Programs).

Wednesday, March 16, 2016

Controlling fire ants in gardens

Fire ant carrying bait back to the nest.  Baits do not have to be
applied directly to a garden to control fire ants living inside a
vegetable garden.  USDA image courtesy Bugwood.
One of the common questions about fire ants concerns control within vegetable gardens. This is an especially common question directed to licensed applicators who work for school districts with school gardens.  It also may be an issue for PMPs servicing residential accounts with home gardens.

A standard, low-risk treatment on commercial, residential and school properties is use of a fire ant bait; however many of the most commonly used baits do not allow direct use in vegetable gardens. Fortunately, there is a work-around.

In most cases the simplest way to get fire ants out of a small- to medium-sized garden is to apply a fast acting fire ant bait around the outside garden perimeter.  This should be a legal application for all fire ant baits (check your label to be sure), and since fire ants do not pay much attention to garden edges, the garden infesting ants will readily pick up bait from the surrounding ground.  Yes the bait does end up inside the garden anyway, but only inside the fire ant nests, where there is no risk of it contaminating leafy vegetables.

For larger gardens or cropland where perimeter treatments might be less effective, several fire ant baits are legal for use.  Spinosad and abamectin-containing baits generally allow garden application (e.g., Clinch®, Fertilome® Come and Get It, and Payback®).  In addition, Extinguish® (but not Extinguish® Plus) fire ant bait containing methoprene has a label that allows use on cropland. However Extinguish is too slow for most gardeners, requiring approximately two months for maximum control.

In addition to baits, mounds can be treated directly with any of several mound drenches labeled for use in gardens.  The eXtension website contains recommendations for a two-step (bait and mound treatment) approach to fire ant control in both conventional and organic vegetable gardens.

Appreciation to Dr. Paul Nester (Texas A&M AgriLife) for supplying some of the information used in this post.