Dr. Murai Éva - Gubányi András szerk.: Parasitologia Hungarica 29-30. (Budapest, 1997)

prene is reflected in the average number of flies staying on the sheets (Fig. 8) or on piglets (Fig. 9). In the last two weeks of the experiment the number of flies observed in both treated rooms was unchanging or even slightly decreased, while in the untreated room high numbers of adult flies could be observed. Data on the average numbers of flies that emerged from manure samples are summarised in Figs 10 and 11. Insects which developed as a result of natural infestation were recorded in rather low numbers (Fig. 10). Nevertheless, more of them emerged in control samples than treated samples. In artificially infested manure samples, where the natural insect population had been killed by cold storage at -20 °C, a significant reduction of adult emergence was detected subsequent to treatments with BIOPREN BM 5 GR (Fig. 11). The difference as compared to the control (Room 3) is considerable. Tkm of lampüng (wwti) Tlmt of umpSrtg (wttki) Fig. 10. Adults indicating the natural fly infestation of manure samples (Formulation type: BIOPREN BM 5 GR = 5 % methoprene; PROTECT B fly killer = 1 % methomyl and 0.2 % sex attractant) Fig. 11. Adult counts obtained after artificial inoculation of manure samples with fly larvae (Formulation type: BIOPREN BM 5 GR = 5 % methoprene; PROTECT B fly killer = 1 % methomyl and 0.2 % sex attractant) DISCUSSION At present several factors hamper the use of biorational larvicides in mosquito and fly control. Spraying operations against adults are easier to organise, give faster positive results, while the expenses of chemicals and treatments are generally low and acceptable. On the other hand, larval breeding sites need to be determined in advance of treatment, a task which is not too difficult in house fly control in animal houses but needs complicated and expensive study in the case of mosquito control. The selective larvicidal agents used here, both the microbial and the chemical ones, are presently more expensive than conventional adulticides. They are generally unstable in nature and, without having protective formulations, remain effective only for a short period of time. The treatment of larval breeding sites may cause some problems in mosquito control when places of different size and scattered location need treatment. However, the selectivity of this type of insect control, when treatments are concentrated to larval habitats, has great significance in comparison to approaches based on repeated sprayings against adults. By treating larval breeding sites,