THE INCIDENCE OF FLYSTRIKE IN SHEEP IN RELATION TO WEATHER CONDITIONS, SHEEP HUSBANDRY, AND THE ABUNDANCE OF THE AUSTRALIAN SHEEP BLOWFLY, LUCILIA-CUPRINA (WIEDEMANN) (DIPTERA, CALLIPHORIDAE)

The incidence of cutaneous myiases (flystrike) in sheep in the Southern Tablelands of New South Wales is examined in relation to the abundance of the Australian sheep blowfly, Lucilia cuprina (Wiedemann), and various management and environmental variables known to affect sheep susceptibility. Regression analysis showed that the incidence of flystrike increased with increases in the density and activity of gravid L. cuprina. Body strike was more predictable than crutch strike, and was positively correlated with monthly rainfall, cloud cover and the rate of pasture growth. Rainfall intensity was also important, with frequent, small falls of rain being more conducive to flystrike than occasional heavy showers. The combination of weather, pasture and fly effects accounted for 76% of the observed variance in body strike and 58% of that for crutch strike. Crutch strike appeared to replace body strike under dry conditions and also when fly densities were low (less than 0.5 gravid females h-1 trap-1), irrespective of weather conditions. The analysis of total strike suggested that rainfall determined overall levels of strike, whereas pasture conditions and cloud cover regulated type of strike.