AgFACT no. 25, August 1999 ISSN 1172-2088 Gorse: control methods Gorse  is  New  Zealand’s  most  prevalent  weed, occupying  about  20,000  ha  of  pasture  land.  It forms  thick,  impenetrable  thickets  that  prevent pasture  growth,  severely  restrict  the  movement and control of stock, harbour vermin, and are a serious   fire   hazard.   This   AgFACT   discusses control methods for gorse. Eradication There is no easy and cheap method of converting dense gorse to productive pasture. The cheapest treatment for large blocks of dense gorse may be to fence them off and wait for them to revert to native bush. Initial clearance costs may be low in relation    to    the    later   costs    of    oversowing, fertiliser, fencing, water reticulation and follow- up  spraying.  It  is  often  better  to  tackle  small areas (5 to 10 ha) at a time than to take on big blocks   that   could   not   be  properly  grazed   or otherwise cared for afterwards. Successful    clearance    of    gorse    requires    a combination of methods: good pasture establishment,  good  grazing  management  and, usually, appropriate follow-up herbicide application. Clearing standing gorse Non-chemical methods, and methods using minimal herbicide On less steep land, ploughing or repeated rotary slashing can be used to control gorse. Repeated rotary  slashing  of  gorse  bushes,  combined  with hard  grazing  by  sheep,  may  eventually  kill  the gorse.   Root-raking   with   a   bulldozer   removes standing   gorse   and   almost   eliminates   stump regrowth   problems,   but   many   gorse   seedling emerge  afterwards,  and  these  are  impossible  to control without herbicides. Large,  isolated  gorse  bushes  can  be  killed  by cutting  them  off  just  above  ground  level  and painting    or    spraying    the    cut   stumps    with Grazon^® in diesel or water (1 part of Grazon^® to 20   parts   of   diesel   or   water),   with   Tordon^® Brushkiller    in    water    (1    part    of    Tordon^® Brushkiller to 20 parts of water), or with Escort^® (5 g Escort^® per litre of water). Gorse burns easily and fiercely, but stumps will regrow and seeds in the soil germinate after even the hottest fire. A heavy roller-crusher (the best treatment),  or  pre-burn  herbicide,  used  several months  before  burning,  results  in  a  hotter  fire, killing more stumps and destroying more sticks. Fire permits are needed in some areas at certain times of the year. A    motorised    knapsack    sprayer    uses    little herbicide  and  kills  small  (up  to  1.5  m  high), scattered gorse bushes, with little chance of drift onto  non-target  species.  An  ultra-low  volume (ULV) attachment further reduces herbicide use. Such sprayers can be used on steep country and among  standing  gorse  bushes.  The  area  to  be treated  should  be  grazed  beforehand  to  expose small  gorse  plants,  but  not  grazed  so  hard  that soft gorse shoots are removed. A marker dye in the spray mix helps guarantee that each bush is sprayed only once. Goats Goats can contain or kill gorse. Goats need to be properly   fenced   into   gorse   blocks,   and   well looked after. On unburnt gorse, at least 20 goats per  ha  are  needed  to make a substantial impact within  a  year.  On  burnt  gorse,  10  goats  per  ha will  keep  regrowth  down  to  20  to  30  cm  high. Goats  will  keep  gorse  in  check  but  may  take several   years   to   destroy   it   completely.   Low density   infestations   of   gorse   can   be   kept   in control by as few as two goats per ha. Biological control The gorse seed weevil (Apion ulicis), introduced to  control gorse,  is found  in  most  gorse  stands. Its  larvae  eat  developing  seeds,  but  are  active only   between   November   and  March,  so  that seeds  produced  at  other  times  of  the  year  are unaffected.  Other  insects  are  being  investigated for their biological control activity. Herbicides Herbicides   registered   for   use   on   gorse   are: activated amitrole (Amitrole 4L and Weedazol Ò ),    Answer Ò ,    Escort^®,    glyphosate (several products), Grazon^®, Reglone^®, Tordon^® Brushkiller, Touchdown^®, Trounce^® Gorsekiller, and Versatill^®. If used carefully, and with regard