Control of Hypericum perforatum L. (St. John's wort) by grazing management
M.H. Campbell, NSW Agriculture, Forest Road, Orange, New South Wales 2800, Australia.
Summary
If an infested pasture is left ungrazed Hypericum perforatum (St. John's wort) becomes dominant. If light infestations are heavily grazed it can be controlled. Heavy infestations on arable land can be controlled by ploughing, sowing improved pastures and grazing heavily. The most difficult situations for the control of the weed are heavy infestations in large paddocks on non-arable land. Here the establishment of a Phalaris aquatica based pasture by the aerial spray-sow technique and heavy grazing has proved successful on fertile soils but the high cost and the risk of failure on infertile soils has limited its use.
Aerial distribution of Trifolium subterraneum seed and fertilizer and grazing only when there is an abundance of pasture has reduced ground cover of H. perforatum by 75%. Heavy set stocking of T. subterraneum-H. perforatum pastures with sheep (black or white) has proved successful on light infestations but unsuccessful on heavy infestations. Cattle are more effective than sheep and a mixture of goats and cattle has proved the most effective grazing management system yet devised. Most of the reports on the effects of grazing management on the control of H. perforatum have come from observations by producers. There is a major need for detailed research into grazing systems to control the weed, particularly on non-arable land.
Plant Protection Quarterly (1997) 12 (2) 97-99.