Integrated management of horehound (Marrubium vulgare L.) in Wyperfeld National Park

John Weiss and Emma Wills, Keith Turnbull Research Institute, Victorian Department of Natural Resources and Environment, CRC for Weed Management Systems, PO Box 48, Frankston, Victoria 3199, Australia.


Summary

Wyperfeld National Park in the north-west Mallee region of Victoria, has a major dilemma with a widespread noxious weed, horehound, Marrubium vulgare. This region, with rainfall below 400 mm per annum, has regular drought periods which kill of many of the mature horehound plants. Due to its prolific seeding, high germination rates, and the large seed bank (in excess of 15 000 seeds m-2), horehound is able to colonize newly disturbed areas and to recruit new seedlings into the weed infestation when conditions are favourable.

Conventional control of horehound using broadacre spray chemical control is unfeasible due to financial cost and off target damage to native plants. A three year experiment in measuring the usefulness of an autumn control burning and reduction in grazing pressure was completed in June 1999. Results indicate that the control burn killed all mature horehound plants and reduced the seed bank down to 1937 seeds m-2 (a 75% reduction). One beneficial effect of the treatments was the tripling in the endemic species abundance in the burnt and ungrazed plots. A reduction in grazing pressure enabled more competition with emerging seedlings, and hence less horehound recruitment. However after three years the burnt and ungrazed seed bank still remained above 1000 seeds m-2.

 

Plant Protection Quarterly (2000) 15 (1) 40-42.