The effects of pasture management on population density and diseases of porina (Lepidoptera: Hepialidae).

Abstract In a field trial carried out at three sites over 2 years at Owaka, South Otago, mob stocking of pasture by sheep in February caused up to 75% mortality of porina (Wiseana spp.) larvae. Mob stocking in March had less effect, suggesting that small larvae, living on or near the soil surface and forming a high proportion of the populations until late February, were most affected. There was no evidence that mob stocking affected the prevalence of virus diseases in porina populations, but microsporidial infections and parasites were higher in mob stocked compared with untreated or haymaking treatments. Haymaking did not effect porina density in the first year; it did, however, effect both porina density in the second year and virus prevalence in each year, the effects varying between sites. The reasons for this were not understood.