It is well known among mosquito entomologists and mosquito abatement personnel that scrap automobile and truck tires often support large populations of certain mosquito species. In southern U.S. two exotic species predominate in tires. These two species (Aedes aegypti and Aedes albopictus) are known to be the principle vectors of Yellow Fever and Dengue, diseases which afflict millions of people in the tropics. In temperate regions of North America, Aedes triseriatus (the native "Eastern Treehole Mosquito") and Aedes atropalpus predominate in scrap tires (1). Based on samples taken in 1992, it is clear that these two species are predominant in tires in Rhode Island (personal observ.). Both of these species are known to be competent vectors of Eastern Equine Encephalitis (EEE) (2) and also of LaCrosse Encephalitis (LACV) (1). EEE is endemic to Rhode Island and fatality rates average near 50%. LACV, although much more prevalent than EEE, usually produces relatively mild symptoms in adults. It can cause serious infection and death in children, however (3). One study documented an association between scrap tires and 15 cases of LACV in Wisconsin in 1979 (4). Finally, dog heartworm, which is a growing problem in temperate North America, can also be transmitted by Ae. triseriatus(5).
 
 

Aedes albopictus (the "Asian Tiger Mosquito") merits special consideration. This species was accidentally transported from Japan to the western hemisphere in the mid-1980's in shipments of used tires. It has since become established in at least 23 states including Indiana and Delaware (6). Based on its native range in Asia, it will likely establish in Rhode Island (7). Its habits are such that it is considered the nation's most dangerous species. That status is because it reproduces rapidly in a wide variety of artificial containers, readily inhabits urban areas, and is a competent vector of EEE (8) and LACV (9). In fact, EEE-infected adults were collected at a large scrap tire pile in Florida in 1991 (6). This finding indicates that this species will readily feed on birds, which are the reservoir for EEE. Since Ae. albopictus is known to feed on a wide variety of mammals, it is considered a potentially effective vector of EEE and LACV.
 
 

It is obvious that eliminating scrap tires will eliminate a prolific mosquito habitat and the associated disease risks. It is also clear that the spread of the Asian Tiger Mosquito has been hastened by interstate shipments of scrap tires (10). Many states have banned importation of scrap tires for this reason. Where elimination is not feasible, mosquito abatement programs may be compelled to suppress mosquito populations at tire piles. This task is problematic and costly, particularly at large piles.
 
 

To suppress adult mosquitoes at a pile requires the frequent use of adulticides, none of which are environmentally benign. Delivering adulticides effectively is problematic at large piles because it is very difficult to penetrate the pile to the depths where the mosquitoes are resting. Larval mosquitoes are likewise a difficult target to reach, as they most frequently inhabit tires beneath the surface of the pile. Two available larvicides are long-lasting and environmentally benign, but the costs become prohibitive at large piles.
 
 

While cost/effectiveness studies of larvicides on large piles are lacking, the results of one study provide a guide for calculation (11). The authors concluded that liquid B.t.i. (a bacteria selective for mosquitoes) would be the most effective at large piles because that formulation penetrated their small piles better than granule or pellet formulations. Unfortunately, the liquid formulation is only effective for 7 to 10 days, requiring numerous treatments during a season. This study calculated the liquid cost to be $2.43 per tire per treatment for the cost of material only. Factoring in the added costs of spraying the pile from a helicopter, it is readily apparent that larviciding is cost-prohibitive at large scrap tire piles.
 
 

References Cited
 
 

(1) DeFoliart, G.R., D.M. Watts, and P.R. Grimstad. 1986. Changing Patterns in Mosquito-borne Arboviruses. J. Amer. Mosq. Cont. Assoc. 2:437-455.
 
 

(2) Means, R.G. 1979. Mosquitoes of New York, Part I: the Genus Aedes.New York State Education Dept. bull. # 430a.
 
 

(3) Harwood, R.F. and M.T. James. 1979. Entomology in Human and Animal Health. Macmillan Publ. Co.
 
 

(4) Hedberg, C.W., J.W. Washburn, and R.D. Sjogren. 1985. The Association of Artificial Containers and LaCrosse Encephalitis Cases in Minnesota, 1979. J. Amer.Mosq. Cont. Assoc. 1:89-90.
 
 

(5) Ludlam, K.W., L.A. Jachowski, and G.F. Otto. 1970. Potential Vectors of Dirofilaria immitis. J. Amer. Vet. Med. Assoc. 157:1354-59.
 
 

(6) Lesser, C.R. 1992. Amer. Mosq. Cont. Assoc. Newsletter. 18:9-11.
 
 

(7) Hawley, W.A. 1988. The Biology of Aedes albopictus. J. Amer. Mosq. Cont. Assoc. supplement # 1.
 
 

(8) Shroyer, D.A. 1986. Aedes albopictus and Arboviruses: a Concise Review of the Literature. J. Amer. Mosq. Cont. Assoc. 2:424-428.
 
 

(9) Grimstad, P.R., J.F. Kobayashi, M. Zhang, and G.B. Craig. 1989. Recently Introduced Aedes albopictus in the United States: Potential Vector of LaCrosse Virus. J. Amer. Mosq. Cont. Assoc. 5:422-427.
 
 

(10) Moore, C.G., D.B. Francy, D.A. Eliason, and T.P. Monath. 1988. Aedes albopictus in the United States: Rapid Spread of a Potential Disease Vector. J. Amer. Mosq. Cont. Assoc. 4:356-361.
 
 

(11) Faget, G.M., P. Perdew, and M. Yates. 1992. Controlling Tigers in Tire Piles. Wing Beats (Amer. Mosq. Cont. Assoc.). 3:8-9.