Vol 4 # 5

Blackfly Issue  
Dr. Bob Stoltz

 This seems to be the year of the blackfly in southwestern Idaho. We’ve been plagued with them for years in south-central and southeastern Idaho. We can speculate on why this year seems to be the year for problems in southwest Idaho and that is all that it would be. I would say that warm conditions coupled with low water levels lead to higher water temperatures, thus a heavier load of organic matter in the water, thus more food for blackflies, thus more blackflies. 
     There are several species of blackflies in Idaho and most of them occur only once per year for a short while. They over winter as larvae in streams, creeks, and rivers. The larvae attach to rocks and trailing vegetation in running water. Unlike mosquitoes, they have to have running water for survival. The larvae have fan-like attachments on their head that filter organic materials from the water and take it to the mouth. After the larvae are mature, they pupate in the water and then emerge as adults. The length of the life cycle depends on the species and water temperatures. Like I said, most adults only live for 2-3 weeks and many only have one generation per year. There are others, however, like Simulium vitattum that have several generations per year. This is the species that we have battled in south-central Idaho for years. After emerging from the rivers in May, it will continue breeding in irrigation canals. Depending on the temperature of the canal, a new hatch of adult flies will emerge every 5-14 days. In the middle of the summer, therefore, you will have new adults emerging daily from the irrigation systems. 
     Now, back to the current problem. We can hope that the flies causing the problems are the one generation varieties and will only be around a short while. This will make them easier to treat and tolerate. If they continue to breed during the summer, we have a different problem to deal with and will have to take a different approach. Control of even the shorter time species will also be difficult and time consuming at best. So be prepared to make several applications. Some other things have also proven effective for certain animals. 
      For horses, These flies love to make mincemeat out of horses ears. Repellants will only last a short time. A new product, Brute, for horses, will keep biting flies away for about three to five days. This is about the best we can expect from any product. Vaseline in the ears makes a physical barrier the flies can’t penetrate and is somewhat messy. The nets that you can buy that fit over the horses ears and eyes are also effective. 
     For other animals, if sprays of permethrin are labeled, they are about as effective as anything. Permethrin has some repellant properties as well as direct toxicity. Don’t put this on lactating dairy animals unless cleared on the label. For dairies, I’d recommend fogs of pyrethrins synergized with PBO. This is a common product, gives a fast knockdown, and very little residual activity.  
     You can use foggers using pyrethrin and PBO over animals in pastures, etc. Check labels carefully and with the appropriate agency (BLM, Forest Service) about using these products in those areas. There could be restrictions. If you fog sheep or cattle (beef or dairy) be prepared to do it daily. You might get by with every few days or just a couple of times if you have one of these “finite” populations that will only be here a short while and have all emerged.  
     For people, using repellants and the mosquito sprays on your clothing may give some relief. The species that bothers us most does not readily feed on humans, however, and mostly hover around our faces being complete nuisances! If you hold your hat high over your head, the flies will orient to that and not your face. This method takes strong arms and stamina, however.  
   

BEFORE USING ANY PRODUCT ON ANY ANIMAL OR SITE, CHECK THE PRODUCT LABEL

     So, we are now all blackfly experts. I hope this information will be helpful. If you get the idea that no control method will be completely satisfactory, you are right- collect $200 and pass GO!  
     Feel free to contact me if you have questions or comments. Happy Bugging!  

UNUSUAL BLACKFLY OUTBREAK IN SOUTHWESTERN IDAHO
Dr. Craig R. Baird

 Blackflies or buffalo gnats have been an unusually serious problem in southwestern Idaho during the spring of 2001.  Since the larvae develop in moving water like rivers, canals and streams, one might expect them to be a problem in high water years.  Why they have become such an unusually difficult pest problem in this low water year is a bit of a mystery.
    Most complaints have come from homeowners asking how they can get rid of the pesky gnats flying around their ears and face.  Gardeners, farmworkers, outdoor laborers, virtually anyone who ventures outside has been subjected to intense attack and annoyance in Washington, Payette, Canyon and parts of Gem counties. But we have also had calls from Ada, Owyhee, and Elmore counties and from Malheur County in Oregon.  Horses are one of the favorite blackfly targets with the gnats zeroing in on the ears and eyes, which become infected and swollen with secondary infections.  Cattle producers have also weighed in with many complaints of blackfly infestations so intense that the cattle bunch up to protect themselves and do not feed.
    In late March we began receiving calls about these annoying gnats and that seems to be the first generation.  After that outbreak tapered off in mid to late April, a new wave of blackflies began to emerge and plague people and livestock alike over a broad area of southwestern Idaho.  With warm weather ahead, we hope the number and intensity of blackfly attack decreases.
    For those still facing blackfly problems there are no surefire cures.  Homeowners can spray the lawn and shrubs and other vegetation around the house with an insecticide registered for those uses but which will offer some control of flies.  Depending on the brand purchased, Dursban, Diazinon, Cygon 2E, and Tempo offer the best hope.  Even these products will probably only reduce blackfly numbers for a few days at best.  Horse owners should utilize the wipe-on products containing permethrin applied to the ears and face of their animals.  The mesh masks are also very helpful in protecting horses.  Cattle owners face a more difficult problem because of herd size and cost of treating the animals. Dust bags help reduce blackflies at low population levels but have been ineffective with the blackfly populations of 2001.  Spraying individual animals around the head and face is about the only way to give positive relief to cattle. Even then only a few days control can be expected.