Mallis and Beyond

Editor’s note: This is the first in a two-part series that Merchant wrote for PCT magazine. See the September issue for more about the conference.

The biannual National Conference on Urban Entomology (NCUE) is always a treat. It’s a relatively small conference with a personal feel. Many attendees know each other personally, and new students get to learn more about urban entomology outside their labs and classrooms. This year’s meeting in Raleigh, N.C., attracted about 200 students, university faculty and industry urban entomologists, including a score of researchers from the joint invasive pest ant conference.

When I attend NCUE, I see folks whose lives and careers I’ve followed for many years, as well as new faces who are the future of our industry. I hear controversy in discussion sessions as researchers politely prod speakers to think more deeply about their research results (entomologists are almost always polite); and sometimes I hear talks that will change the way I view structural pest control. While there were no real revelations at this meeting, many of the talks I heard this year fell into the category of “baby steps” toward better pest control and a deeper understanding of the biology of structural pests.

DISTINGUISHED ACHIEVEMENT AWARD. Every NCUE meeting has a Distinguished Achievement Award recipient. This year’s honor went to Brian Forschler, a respected termite researcher from the University of Georgia. It was his job to open the meeting with a tribute to Arnold Mallis, whom many of you know by his “10-pound” Handbook of Pest Control.

Forschler noted that Mallis filled a desperate need at the time for science-based information on household insect pests. Though he had little to say about IPM (the concept hadn’t been formally proposed), in his books he summarized critical biological information upon which IPM programs could later be built. Mallis taught us that urban entomology is built upon a firm foundation of education and engagement with its stakeholders. Forschler urged each attendee, especially each student, to consider new ways to engage outsiders with urban entomology, while being the same consummate entomologist, naturalist and observer of insects as Arnold Mallis.

After Forschler’s session, the meeting began with papers from student award winners. When I listen to students, I always keep in mind that today’s students are tomorrow’s experts. In just a few years these will be the folks making the rounds at continuing education units (CEUs) meetings for NPMA and other professional gatherings, so it pays to listen and make note of the new faces.

STUDENT TALKS. Emily Vernon, Bachelor of Science Student Award winner, came from North Carolina State University where she studies Blattabacterium, a genus of symbiotic bacteria that live within special bacteria-hosting cells of cockroaches. These bacteria, she proposed, are essential to the German cockroach’s ability to survive in nitrogen-poor environments. In her research with 16S ribosomal RNA primers, she detected high levels of variability in Blattabacterium in field populations of cockroaches, leading her to pose the question: “If we can manipulate Blattabacterium in the cockroach, might we be able to control cockroaches in the field?” I don’t know the answer, but I do know that when I was her age my most profound questions dealt with where to go for pizza on Friday night. Wow!

Master’s Student Award winner, Danielle Hoefele, Simon Fraser University, tackled a whole new structural pest: the European fire ant, Myrmica rubra. Think of it as a fire ant for the north. The European fire ant is spreading into British Columbia, Washington state, New England and eastern Canada. It’s an aggressive ant with a sting that itches up to 10 days. Hoefele looked for different food sources that might work well in a fire ant bait. She found that baits combining carbohydrates and proteins were most attractive. Ultimately, she hopes to design a custom bait to provide a much-needed control option for this pest.

Sudip Gaire from Purdue University was the Ph.D. Student Award winner for his studies on the effects of plant essential oils against bed bugs. Gaire is pursuing more effective, safer, natural insecticides for bed bugs. By looking at plant essential oils that have not previously been tested, he hopes to discover better options for controlling insecticide-resistant bed bugs. He found carvacol, thymol and citronellic acid to be the most toxic plant oils, none of which are currently in use against bed bugs. It may be years before these products are successfully brought to market, but Gaire is starting the process, and he reminded me that the field of essential oils for pest control is ripe for mining.

In another student paper, Sanjay Basnet from the University of Nebraska is looking at ways to turn the bed bug’s own genetic material against itself. Interference RNA, or RNAi, are small RNA strings found naturally in the cells that help block expression of target genes. A few years back, someone got the bright idea that if we could find the right RNAi strings, we might be able to use them as insecticides to turn off genes that are critical for an insect’s survival or reproduction. Basnet thinks he may have found such an RNAi strand — one that can reduce egg production in bed bugs. When injected into bed bugs, this natural and biodegradable molecule reduced average daily egg production from six per day to zero per day at three and four weeks after treatment. Much more work is needed to bring this kind of technology to your company, but it’s always encouraging to hear about any progress in this area.

One of the rising stars of urban entomology is Zach DeVries, Ph.D. student at North Carolina State under major professor Coby Schal. DeVries is looking at a previously ignored component of bed bug aggregation pheromone called histamine. You’ve probably heard of histamine. It’s an important chemical that our bodies produce to regulate our local immune response. On the positive side, histamine allows capillaries to become more permeable to our white blood cells so they can engage pathogens during an infection. On the downside, it’s the chemical that causes inflammation and itching after an insect bite or exposure to an allergen. That’s why you may take an antihistamine drug for a runny nose or itchy eyes. Histamine also affects numerous organs, causes increases in heart rate and difficulty breathing.

DeVries and colleagues inspected house dust from homes with and without bed bugs. They found up to 25 times higher levels of histamine in bed bug-infested homes. They also found that histamine persisted for three to six months after an infestation had been eliminated. Whether these relatively low levels of histamine associated with bed bugs will have chronic effects on human health is unknown. But if significant, DeVries’ team’s discovery could be as important to pest control as the discovery of the link between German cockroaches and asthma in the 1990s.

DeVries also gave a second, more controversial, paper on progress towards developing a liquid bait for bed bugs. He suggests that liquid baits might offer an alternative insecticide-delivery method that could bypass at least one of the resistance strategies used by bed bugs (such as thickened, pesticide resistant cuticles). So far, DeVries has identified good active ingredients (such as fipronil, neonicotinoids and DMSO) for such a bait. The feeding attractant for bed bugs is more of a challenge, however. Bed bugs eat blood of course, which is not likely to be stable in a bait formulation. And who wants blood-filled bait stations around their home?

He found that simple salt water, with or without the natural cellular compound adenosine triphosphate (ATP), made an attractive feeding stimulant for bed bugs. The challenge, he argues, is to come up with a way to deliver this tasty insecticide to hungry bed bugs. But some listeners gently challenged DeVries to demonstrate how baiting might be more effective than, say, a good trap. The reason that most cockroach, termite and ant baits are so effective is that they don’t just kill the individuals that come to the bait. They are effective because they kill the feeders and their companions. This happens when other cockroaches eat the feces or dead bodies of bait-fed cockroaches, or when ants and termites share their toxic meals with nestmates. At this point, it’s hard to see how you might get secondary kill with bed bugs. Time will tell whether NCSU researchers will demonstrate the practicality of blood-mimicking bait stations; but it’s a thought-provoking idea, and I’m glad someone is exploring it.

Whew. That was a summary of some of the things I learned from students at NCUE last month. In my next installment, I’ll cover some of the highlights from veteran urban entomologists in Raleigh.

The author is an entomology specialist for Texas AgriLife Extension. Readers can contact him via email at mmerchant@giemedia.com.