Control ofWiseanaspp. (Lepidoptera: Hepialidae) by sheep grazing in South Otago

Abstract

Abstract Porina damage to pasture is a serious problem in Otago and Southland and low-cost control methods such as heavy stocking are attractive alternatives to the use of insecticides. In South Otago, density of larvae ofporina (Wiseana spp.) in pasture was reduced on average by 69% by grazing with 1000 ewes/ha for three periods of 3–5 days in January, February, and March, and by 32% by one period of 3–5 days in February. Similarly, four, 3day periods of grazing at 500 eweslha caused a 47% average reduction, and corresponding mowing of the pasture to 1 em in height with a rotary mower caused a 32–42% reduction. Three periods of grazing with 1000 ewes/ha increased pasture production by 34% in the following spring and early summer. Four periods of grazing at 500 ewes/ha increased production by 35% at one site. Single periods of grazing and mowing had no effect on pasture yield. Multiple grazings of 3–5 days with 500–1000 ewes/ha is a viable option for porina control.