COLLEGE OF COMPUTER, MATHEMATICAL AND NATURAL SCIENCES 

 DEPARTMENT OF ENTOMOLOGY 

 

 4112 Plant Sciences Building 

 College Park. Maryland 20742-4454 

 301.405.3911 TEL 301.314.9290 FAX 

 www.entomology.umd.edu 

January 26, 2012 

Dr. Russell Wasem 

Chemical Review Manager 

Hexaflumuron Registration Review 

Pesticide Re-Evaluation Division (PRD) 

U.S. Environmental Protection Agency 

Dear Dr. Wasem: 

I have been consulting with Dow AgroSciences on honey bee exposure issues and have 

been asked specifically to assess the potential threat of the Hex-Pro Termite Baiting 

System to Apis and non-Apis species. As you may know, I am not a termite expert but 

one of my current research areas addresses exposure risks and sub-lethal effects of 

pesticides on honey bee health. So I feel confident about reviewing this issue and offering 

an unbiased assessment. To actually see the baiting system in application, Ms. Jessi 

McKinney, Dow’s regional technical representative, arranged a field visit in December to 

a treated site, where I examined the placement of the in-ground and above-ground HexPro products, and discussed their uses with Mr. Wayne White, a certified PCO from 

American Pest Management Company. 

My immediate impression with this baiting system is that it ideally represents a remedial 

IPM approach because the stations baited with untreated wood only are used first to 

monitor for termite activity. If activity is detected, the wood is replaced with a bait matrix 

of hexaflumuron-treated cellulose. And then after the termite infestation is controlled, 

untreated wood is again placed in the station to continue monitoring for re-infestations. 

As you know, the alternative approach is to apply long-residual insecticides 

preventatively by soil incorporation or soil injection around structures where termites 

may be active. In my opinion, these alternative methods pose a greater potential for 

exposure to non-target organisms, including bees, especially because several active 

ingredients are soil-applied systemics. I bring up this point because I believe that 

comparative potential for bee exposure of all control methods available should be 

considered in your decision. 

I reviewed the technical information on the Hex-Pro baiting system and Dow’s rationale 

statement for a Waiver of Data. With regards to the in-ground application, the bait station 
will not expose bees to the active ingredient hexaflumuron for several reasons. First, the 

plastic tube that houses the cellulose bait has slots to allow termites to enter. These slots 

are 2.5 mm wide, which are too small for honey bees or ground-nesting native bees to 

enter the bait tube. The smaller native species that nest underground in burrow and 

tunnels are halictid and andrenid bees, and the smallest species found in the U.S. is 5-6 

mm in size. Second, there is no reason why ground-nesting bees would be attracted to the 

bait station as a nesting site or food source. All species that nest in the ground do not 

utilize wood as a nesting site. Third, ground-dwelling bees make nests below ground as a 

shelter for their offspring. They construct chambers at the end of tunnels and provision 

them with nectar and pollen – food for the bee larvae. Adult bees do not forage in the 

ground while constructing and provisioning tunnels, and larvae feed exclusively on the 

provisioned food. Finally, the nesting biology of the halictid and andrenid bees suggests 

that their burrows and tunnels are unlikely to be in areas around structures where bait 

stations would be placed. Most mining bees prefer areas where vegetation is sparse and 

the soil is loose - conditions that are not typical around the foundation of houses and 

other structures. 

It is my understanding that the above-ground termite baiting system is used primarily 

inside structures, attached flush with screws to the surface wall where termite activity has 

been detected. A common site is the crawl space below sections of structures where 

gallery tubes are present and provide a sealed conduit for termites to move from the 

colony in the ground to the source of wood above. The bait station is placed over these 

galleries and tightly sealed to the surface with a provided gasket and often with the use of 

caulk. This prevents entry of light which would repel termites and thus reduce the 

efficacy of the bait station. Thus, if properly installed, the above-ground bait product will 

not expose bees because there is no way for bees to gain access to the bait, even if they 

were attracted to it. 

In short, based on the foraging biology and nesting behavior of bees, and the physical 

exclusion of the bait stations, I concur with the explanations in Dow’s rationale statement 

for a Waiver of Data. After a review of the Hex-Pro Termite Baiting System and having 

observed its application in the field, I am convinced that this product, whether used in- or 

above-ground will pose no harm to Apis and non-Apis species. If there is a need to 

discuss this issue in more detail, I can be contacted at galen@umd.edu or 202-812-9828. 

Respectfully, 

Galen P. Dively 

Emeritus Professor/IPM Consultant