Pesticide applications for fly control Granular baits

Public Health Significance of Urban Pests 225 Also, exhaust vents and air intakes should be screened. Moreover, if properly installed and maintained, mechanical air curtains or blowers mounted over and around outside doors can be beneficial in preventing flies from entering.

7.8.4. Pesticide applications for fly control

Pesticides are not widely used for controlling flies in urban areas. Most urban fly popu- lations are adults, and it is difficult to treat local populations effectively with pesticides. The exception is during times of large-scale disasters, when fly populations can reach catastrophic levels very quickly. During these situations, aerial applications of labelled pesticides may result in exposing some people to the pesticides. However, the expected public exposure in urban areas should be minimal. Around structures, the only pesticide applications made, are those applied topically to outdoor walls where flies rest. Pest control operators make these applications, and the general public receives little or no exposure. Topically applied residual pesticides are available, but not highly recommen- ded. Unless applied to known fly resting sites, and reapplied regularly, these chemicals may increase the chances of developing pesticide resistance in local fly populations Hemingway Ranson, 2000. In private dwellings, commercial aerosol pesticides should give adequate protection against small numbers of flies that enter. The only other pesticides in use around buil- dings are granular baits, and these are localized in bait stations and are out of the reach of people and animals. There still may be some indoor or outdoor spray systems in ope- ration, with pyrethrins or synthetic pyrethroids most likely used as toxicants. Whenever possible, pesticide use should be minimized in urban areas. For a review of fly-management techniques, including pesticides, see Farkas Hogsette 2000.

7.8.5 Granular baits

These baits are in granular form and can be placed in bait stations or scattered on the ground, depending on label restrictions and local regulations. Baits contain stomach poi- sons and are best used for housefly management. Most of the older granular baits on the market contain methomyl as the active ingredient, but there are at least two new baits on the market with new active ingredients spinosad and imidacloprid that should prove useful in urban areas, if applied properly. Unless flies are present in large numbers on patios or in garden areas, these baits would not normally be recommended for home owners or apartment dwellers. Granular baits have been used successfully around com- mercial establishments, such as restaurants and supermarkets, to manage moderate fly populations in the outer rear areas of stores. Bait stations are available, and they consist of granular baits affixed to cardboard strips and encased in a protective mesh. These can be hung or attached to walls to attract and kill flies. Granular baits can be used to quic- kly reduce housefly populations, but seldom can the use of these baits alone control hou- seflies. Flies 224 1.surveillance to identify their presence, species population size and conditions that favour breeding; 2.sustained monitoring of fly populations and conditions that favour breeding; 3.evaluation of survey results; 4.initiation of control measures when established thresholds have been passed and noti- fication of appropriate units responsible for conducting control measures; and 5.continued surveillance, to determine the success of control measures. An effective surveillance programme must have a mechanism for determining the need for control measures. Surveillance usually, but not always, means trapping. Such trap- ping should be conducted at a standardized time and at the same locations. Locations must be accurately identified, so the trap will be placed in the same location for each sub- sequent survey. Traps must be selected carefully to determine the fly species responsible for the problem. Most flies in urban areas will be in the adult stage; larval populations, however, might be encountered if suitable habitats such as garbage and sewage are avai- lable. An index of adult flies may be obtained most efficiently by so-called fly grills Scudder, 1947, 1949, but sticky traps, fly baits, spot counts and many other methods can be used. Larval or pupal specimens, or both, can be found by checking the breeding habi- tats and, if necessary, they can be identified with appropriate taxonomic keys. Because proper identification in the field can be critical, it is important that inspectors be familiar with all life stages. The presence of flies does not automatically initiate a recommendation for control. To help predict when control measures are needed, thresholds are established. The thres- hold value itself is an index calculated from surveillance data. Continuous surveillance over an extended period of time may be required to establish reliable threshold values. Long-term surveillance data may also reveal identifiable trends that can be used to pro- tect the people involved, by allowing control measures to be initiated just before a serious fly problem occurs. Threshold values will vary at different geographical locations, depen- ding on such factors as species, area involved, habitat, collection technique, number of complaints and disease potential. After gaining some experience, a nuisance threshold may be established. In residential areas, for example, if fly complaints are numerous when the average grill index is 25 flies a week or whatever the sampling interval may be, then this may be at or near the nuisance threshold.

7.8.3. Fly exclusion practices