Gorse Management and Control:

Dozing, ripping and root raking (1151) is effective on established stands, providing cultivation, herbicides or grazing are used to control seedlings. Burning does not provide much control but it does encourage seed to germinate so it may be killed by cultivation, herbicides or grazing. Stands are usually rolled or desiccated before burning to achieve a fire that is as hot as possible. Seedlings are sensitive to competition so vigorous pastures should be planted as soon as the major infestation has been controlled. Goats are particularly effective for controlling Gorse seedlings and regrowth at stocking rates of 5 wethers per ha (1152). In patchy infestations sheep are used to consume pasture so the goats concentrate on the Gorse.
Mowing and slashing are generally ineffective because regrowth normally occurs.
Metsulfuron, triclopyr, Grazon® and glyphosate are the most commonly used herbicides. These all work better when applied with an organosilicone surfactant such as Pulse® Penetrant or Silwet® (1153).
The best time for spraying hormone herbicides was in October when the new growth was 2.5 cm long. Good control was achieved from October to January but there was some regrowth from the base. Spraying from February to September resulted in regrowth for all parts of the desiccated stems in NZ (1154).
The best time for spraying hormone herbicides on seedlings was between 9 am and 3 pm (1141).
The maximum amount of spray is retained in March when new and old foliage is present but the best time to spray is usually from October to December with 2,4,5-T (1155).
For new plantations in New Zealand they roll then burn in spring, spray with triclopyr (e.g. Garlon®) in summer, rip in March, respray in May and plant in late winter.
Cross country vehicles (e.g. Gnat®) are fitted with motorised blowers for controlling scattered infestations in NZ (1156, 1157). The Husqvarna® Multi 300 clearing saw blade is suitable for clearing gorse (1158).
Control with CDA sprayers and 2,4,5-T was better when droplets were <120um (1159).
1160 has looked at control on cliffs.
Integrated control
1113 has reviewed a range of controls and suggests integration of a number of control techniques and rehabilitation of the site is required.
Best control was burning then rotationally grazing with >20 goats/ha or a sheep goat combination. 20 sheep/ha rotationally grazed with mechanical slashing or spraying was also effective. Once plants are eradicated, sheep and pasture competition kept the area gorse free. On unburnt areas, heavy continuous grazing with goats for 4-5 years was required for gorse control (1161).
Crushing gorse with a roller before aids herbicide penetration giving higher levels of control which were then burnt before planting pines. The combination of cultural plus chemical control was required good control (1162).
Burning then spraying 3 and 7 months later gave high levels of control but not eradication (1163).
Burning in spring, then spraying in January when regrowth was 5-7 cm tall and repeating in late autumn after seedlings have emerged and some coppice regrowth with 2,4,5-T plus picloram gave high levels of control and reduced seedling establishment by 90-95% over the next 4 years in NZ (1164).
Burning then applying herbicide to young regrowth is better because complex waxes form on foliage older the 3 months (1062).
Trampling, long rotation grazing, liming and grass competition reduced gorse seedling survival (1165). Grazing with trampling is better than mowing for decreasing gorse seedling survival (1166).
Survival of gorse seedlings was less than 2% when grass, white clover, grazing and N plus P fertilizer used (1165).
1167 has control techniques from the 70's which consisted of combinations of spraying, burning, grazing and follow up.
Spraying then cutting 24 hours to 2 months later gave good control and only 6% re shot within 15 months (1168).
Lime super and N reduced seedling emergence. Species of cover crop had no effect (1169).
Burning followed by reseeding pasture, fertilizing, grazing with sheep and cattle and spraying gorse remnants for 3 years gave effective control (1170).
Grazing
Goats prefer gorse (20% of diet) and grass and eat little clover, sheep prefer grass and clover and eat little (0.1% diet) gorse (1171, 1172) and provide useful control in NZ (1173).

Gorse regrowth was least with 20 goats/ha and most with 10 sheep/ha. There was no difference between rotational or continuous grazing. Seedling numbers were not affected by stock type or grazing management (1174).
After gorse was burnt and the area reseeded to pasture gorse was reduced to negligible levels by goats or goat plus sheep grazing but sheep alone were ineffective (1175).
Gorse can supply maintenance feed year round for goats and prefer foliage, flowers and green bark (1065).
Goats at high stocking rates were required for good control (1176).
Hardness and sharpness of spines in winter cause total rejection of gorse by sheep but not goats (1177).
Voluntary ME intake by sheep on gorse was never above maintenance and for goats it was 1.6, 0.82, 0.72 and 0.41 of maintenance in late spring, summer, autumn and winter respectively (1177).
A single grazing up to 9 months after germination gave good seedling control and grazing could be delayed up to 12 months if it was repeated (1178). Rotational grazing gave better control than continuous grazing (1165).
Grazing reduced seedling population by 90% over 2 years (1179).
Grazing alone reduced seedling numbers by 30-60% in pure stands and when in competition with pasture reduced numbers by 70-100% (1180).
Fallow deer rarely eat gorse (1181).
1182 has field versus animal house feed preference data for sheep and goats given access to gorse and other species.
1183 consider goats, sheep and cattle for weed control (1183).
Grazing by cows or a mix of cows and sheep provided some suppression of young gorse (1184) For control, 2 applications of herbicide were needed on areas that were grazed by cows alone (1185).
Grazing is used in NZ plantations for gorse and other weed control (1186).
Shading and defoliation don't kill gorse seedlings unless cut well below the growing tip (1187).
Burning
Burning is useful in combination with herbicides but is rarely effective by itself (1188) and may cause increased levels of gorse (1189, 1190).
5.5 L/ha 2,4,5-T plus 5.5 L/ha 2,4-D plus 22-33 kg/ha sodium chlorate or borate plus 11 L/ha diesel plus water to 225-450 L/ha applied 6 weeks before burning as a conditioner is good. Sodium chlorate may be substituted by 11 L/ha paraquat in the mix above (1191).
50% of the N in the plant is lost by volatilization when burnt (1192).
Grasses are most flammable followed by gorse and pine litters then blue gum litter (1193).
Fire temperatures in 20 year old gorse were 800c at 60 cm up to 700c at 0 cm and 22c at -5 cm. No effect on fungi a day after fire but bacterial:fungi ratio increased with time as ash increased pH (1194).
Soil temperatures in the top 2 mm reached 237 deg C and at 40 mm only increased by 6 deg C. Burning reduced the seed bank from 2600/m2 to 1000/m2 (1082).
In natural vegetation fire probably prevents the transition from gorse domination to evergreen forest and frequent fires lead to gorse domination (1107). However, if fire is followed by intensive grazing then gorse decreases (1195).
10 months after burning 46% of stems had regrown (1082).
Regrowth from stumps occurred after a flash fire and regrowth from seedlings occurred after a humus fire in NZ (1196).
Water relations 20 months after fire are similar to unburnt areas with through fall being 88% of gross rain after fire decreasing to a 60% plateau 4 years after fire (1197).
50-75% of above ground nutrients lost due to volatilization and smoke with burning and only 3% end up on the soil surface in ash and significant losses due to leaching and sediment erosion with the first rains. 2.5-3.5 g/m2 N and 6.5-9 g/m2 K lost due to burning. N and K inputs into the soil were less on burnt areas versus unburnt areas but were similar for P, Ca, Mg and Na (1198).
Keep bare soil to less than 85% by burning when moist litter is present to prevent soil erosion after the burn (1199).
Fertilizers
Keeping the ratio of N:P high favours grass over gorse (1056).
Lime slightly reduces seedling establishment mainly by increasing competition by other species (1200).
Gorse was more invasive on low N sites. N and lime retarded seedling growth whilst P increased seedling growth and K caused little response in white clover/perennial ryegrass/gorse swards. Mature gorse increased its growth when N was added but showed little response to lime (1201).
Herbicides
Mist blowers gave good control at all times of the year where the gorse gun was only effective from November to February using 2,4,5-T (1202).
2,4,5-T
Generally provided good levels of control but is no longer available.
Burn in February, spray regrowth at 15-20 cm high and repeat in 12 months is effective. October spray then burn and repeat in 6 months was less effective. Ground spraying more effective than aerial spray (1203).
Diesel and picloram improved control in autumn/winter applications and dicamba, glyphosate, paraquat and diquat had no effect or reduced control (1204).
Double strength used for winter applications and no advantage found in adding picloram or diquat (1205).
Water stress before spraying caused a large decrease in control but stress after spraying had little effect (1206).
Better in summer wet areas than summer dry areas. Addition of picloram improved control in summer dry areas (1207)
Absorption varied from 20-98% depending on mixing partners (1208).
Young spines absorb more 2,4,5-T than older spines. Diesel reduces this difference (1209).
2,4-D
Applied in diesel as a cut stump treatment was less effective than triclopyr (1210).
3,6-DCPA (3,6-dichloropicolinic acid)
Better than picloram (1211).
Amitrole
Provided good control usually (1212).
Ammonium sulphamate
Provided poor control (1212).
Clopyralid
0.5% clopyralid plus 0.5% crop oil applied at early bloom as a directed spray gave good control after 6 months and was slower acting than triclopyr at the same rates. Broadcast rates of 1.12kg/ha? gave 37.5% control (1213).
Addition of Silwet® increased uptake more than diesel (1214).
Dicamba
Provided good control in good conditions (1215).
Organosilicone surfactant Silwet® L77 and pyrrolidone surfactant Agrsisolve® 3 increased uptake 24 hours after application (1216).
Addition of dicamba to 2,4,5-T improved control (1217).
Fenoprop
Killed all stems and 56% of root crowns at 5.4 kg/ha on mature gorse. Addition of picloram increased root crown kill (1218).
Little movement from the treated branches to laterals or roots (1208).
Glufosinate
Provided poor control (1212).
Glyphosate
Autumn application is better than early or midsummer. Addition of organosilicone adjuvants improved control (1219). However, 1220 claims there is little effect of time of spraying and best results are on mature foliage.
Glyphosate alone gave poor control and glyphosate plus organosilicone adjuvant gave apical death after 24 weeks but regrowth occurred on the mid and lower stem sections (1221).
Glyphosate plus Triton® X45 of Silwet® L77 provided good control in NZ (1212).
Organosilicone adjuvants at >0.5% improved the rainfastness of glyphosate (1221, 1222, 1223).
In potted gorse, 6.5 kg/ha glyphosate gave 73% control and 2.2 kg/ha plus 1-2 % organosilicone adjuvant (1224).
Rates of 540 g.a.i/100 L only provided good control when gorse was in the soft spine, pre flowering stage when applied without surfactants. Addition of 0.05% Triton® X45 (octylphenoxypolyethoxyethanol) or 0.25% Silwet® L77 (organosilicone) gave good control at all stages of gorse with 360 g.a.i/100 L (1225).
Organosilicone surfactant Silwet® L77 and pyrrolidone surfactant Agrsisolve® 3 increased uptake 24 hours after application (1216).
No difference between Pulse® and Freeway® organosilicone adjuvants and both increased absorption and translocation with 0.5% concentration better than 0.2% (1226).
Silwet® L-77 (or Pulse®) generally increased uptake and the effect depends on plant age and environmental conditions (1227).
On seedlings, 2 kg/ha best in December after all seedlings emerged and were <2 cm high (1228).
Glyphosate in water as a cut stump treatment less effective than triclopyr (1210).
Glyphosate plus or minus Agral®, Citowet®, Triton® X-45 and Silwet® was toxic to gorse spider mite (1229).
Hexazinone
Hexazinone suppressed young gorse and was tolerated by pines at rates up to 3600 g.a.i./ha ().1230
Addition of organosilicone only had a slight effect on control (1219).
On seedlings, 2 kg/ha best in December after all seedlings emerged and were <2 cm high and gave 100% control and inhibited further germinations (1228).
Imazapyr
Better control when organosilicone or other surfactant used (1231).
Metsulfuron-methyl
Addition of organosilicone adjuvants improved control (1219). Organosilicone surfactant Silwet® L77 and pyrrolidone surfactant Agrsisolve® 3 increased uptake 24 hours after application (1216).
200 g/ha metsulfuron alone or 150 g/ha metsulfuron with 0.3% organosilicone or 0.25% Triton® X-45 adjuvant provided 100% control of 2 year old gorse seedlings. At 100 g/ha with or without adjuvants control was less than 100% (1232).
Good control at 37.5 g.a.i./100 L water when applied during active growth (1233).
300 g/ha plus surfactant required for midsummer applications and more for winter applications and not as good as 2,4,5-T plus picloram for long term control (1234).
At 200 g/300 L water plus or minus Silwet® applied monthly the uptake was 53-57% in May-August and 66-77% in September-October. 6-18% of this translocated indicating that time of spraying has little effect on efficacy (1220).
Best uptake with best wetting but translocation reduced so 0.3% Silwet® L-77 was best and a 10 fold difference in metsulfuron had little effect on uptake or translocation and late winter/spring much better than autumn (1235).
Organosilicone adjuvants increased uptake and translocation of metsulfuron and there was little difference between Break-Thru® S 240 + S 278, Break-Thru® S240 and Silwet® L-77 at 0.1-0.5% v/v and 0.5% better than lower rates (1236).
90 g/ha gave good control with L-77 and poor with L-7607, nonylphenoxypolyethoxyethanol (e.g. Triton®) or none (1237). Lowest rate for good control was 35 g/ha metsulfuron plus 0.2% L-77 (1237)
Provided reliable control in NZ (1212).
Metsulfuron with Agral®, Citowet® and Triton® X-45 did not harm gorse spider mites (1229).
No effect of water volume of 46 vs 202 L/ha (VMD 295 vs 839pm) on aerial spraying of gorse with 275 g/ha metsulfuron plus 192 mL/ha Silwet® L-77 in March and bulldozed 10 months later then burnt (1238).
MSMA
9 L/ha and burn in October followed by 9 L/ha in March effective (1203).
Paraquat
Mixed with 2,4,5-T applied in April after a February burn was effective in NZ (1239, 1240).
Paraquat better than diquat on seedlings ().1241
Picloram
Good control with pellets in Hawaii (1104).
Generally increases the amount of root crown kill but depends on partner herbicide (1242).
Mixed with 2,4,5-T applied in April after a February burn was effective in NZ (1240, 1239).
Organosilicone surfactant Silwet® L77 and pyrrolidone surfactant Agrsisolve® 3 increased uptake 24 hours after application (1216). L-77 improved picloram activity (1237).
Translocated freely to sites of active growth such as the stem apex and root nodules in vegetative plants and floral organs in reproductive plants (1243). However, 1244 found little movement from the treated branches to laterals or roots.
Addition to 2,4,5-T improved control of mature plants (1217).
Addition of picloram to triclopyr didn't improve seedling control or reduce further establishment (1179) and similar results have been noted in WA.
1.1 kg applied by air took 15 months to reach levels (73-98% breakdown) allowing sub clover establishment on 75% of sites in NZ and residues from 0.5 kg were safe after 3-6 months with the main effect being soil type (1245).
Winter treatments with 2,4,5-T were better when picloram was added (1246).
Picloram moves from point of application to the roots but not to other stems (1247).
Surfactants, removing cuticular wax and lowering pH increased absorption from 44% to 350% whereas misting (high RH) increased absorption by 82-107% (1247).
Absorption ceases after 10 hours but is resumed on re wetting (1063).
Picloram at 125 g/1000 L gave better control of protected foliage than 2,4,5-T dicamba or diquat and control of protected foliage was greater in summer than winter and was greater for upper than lower branches (1248).
Control with picloram was reduced if gorse was water stressed both before and after application but OK if only one period of water stress and less (1206).
Addition of picloram to 2,4,5-T improved control in summer dry areas (1207)
SF 06406 (2,4-D ester + dicamba + triclopyr)
Worked well in Scotland in summer (1249).
Simazine
Simazine at 12 kg/ha inhibited gorse seed establishment and 8 kg/ha gave partial control (1203).
Tebuthiuron
Not very good for gorse control at 2-6 kg/ha (1250).
Gave variable results in NZ (1212).
Terbuthylazine
Was the best of the triazines for pre emergent control (1251).
Thiazafluron
10 kg/ha provided good control provided 200 mm rain fell within 3 months of application. Toxic to pines <2 m tall. Stem injection was ineffective. Soil residues toxic to some pasture species, Pinus radiata and Maize for at least 12 months.
Triclopyr
Pinus radiata seedlings tolerated up to 600 g/ha triclopyr when applied before the flush of new growth in spring. This could be used for gorse suppression and was safer than triclopyr plus picloram (1117).
Triclopyr as the salt or ester at 1-4 kg/ha selectively controlled gorse in young pines and transplant lines (1252).
Some organosilicone adjuvants improved the stomatal uptake and reduced surface tension to <25 mN/m and contact angle to < 20 degrees on gorse treated with trimethylamine formulations but had little effect on butoxyethyl ester formulations which entered by a transcuticular pathway (1131). Control was better with organosilicone L-77 than L-7607 than nonylphenoxypolyethoxyethanol (e.g. Triton®) than none for amine formulation but no effect for ester (1237).
1% triclopyr plus 0.5% oil applied as a directed spray at early bloom gave excellent control as did 1.12 kg/ha plus 1.5% crop oil applied as a broadcast treatment (1213).
Organosilicone surfactant Silwet® L77 and pyrrolidone surfactant Agrsisolve® 3 increased uptake of triclopyr amine but not ester 24 hours after application (1216).
480 g/ha applied in autumn gave the best control in the UK (1253).
Triclopyr amine at 2.7 kg/ha and triclopyr ester at 2.4 kg/ha gave good control in summer (July and August in UK) but was safer on pines in August (1147).
1.5 kg/ha in October to April gave good control of seedlings up to 3 years old and higher rates were similar (1179).
Ester formulations mixed in diesel and applied all over the cut stumps provided very high levels of control at any time of the year and up to 1 week after cutting. Neat amine formulations applied to the cut was also effective (1210).
460 g/ha provided adequate control in Europe hedgerows and rail embankments (1254).
Basal bark applications of triclopyr ester plus crop oil gave 77% control (1255).
Drizzle application of 1 kg/ha triclopyr plus crop oil gave 88% defoliation at 6 months after treatment (1255).
Triclopyr and triclopyr/picloram plus or minus Agral®, Citowet®, Triton® X-45 and Silwet® were toxic to gorse spider mite (1229).
1256 has chemical and physical properties, toxicology and behaviour in the plant for triclopyr.
100 g out of 3750 g (2.7%) of triclopyr entered streams adjacent to sprayed areas mainly with the first significant rainfall after spraying but no residue found at the catchment outlet. Half life in soil was 100 days and in grass was 30 days. Underneath gorse bushes soil levels increased for 32 days then declined like exposed sites (1257).
TTA (Terbumeton + terbuthylazine + aminotriazole)
On seedlings, 0.5 + 0.5 +0.25 kg/ha best in December after all seedlings emerged and were <2 cm high. At 2 + 2 + 1 kg/ha it inhibited further germinations (1228).

Thresholds:

Eradication strategies:

Gorse is difficult to eradicate (1218) because it rapidly invades disturbed areas and seedlings will keep emerging for many years after the last plants have been removed. Soil seed banks can exceed 10,000 seeds/m2. An integrated program is likely to be most successful as no single method gives complete control (1258). Try to conduct an eradication campaign on a district basis to reduce seed being carried in by birds. Control the established infestations by rolling, hot burning, and then cultivation or spraying with 100 mL Grazon plus 25 mL Pulse® in 10 L water when the plants are actively growing in spring to autumn. Establish vigorous grasses and fertilise with nitrogen. Graze with goats and spot spray trouble spots with metsulfuron or Garlon. Establish leguminous species in the following season and keep grazing with goats. Use a blanket wiper with metsulfuron to treat Gorse that escapes the goats. On areas that can't be grazed, apply Grazon® annually until few seedlings appear. Two years after the last Grazon® spray, replant species that will provide complete shade as quickly as possible. Control seedlings and small plants manually or spray with 100 mL glyphosate(450g/L) in 10 L water or paint with 1 L glyphosate(450g/L) in 2 L water.
Use Pulse® Penetrant with all foliar herbicides.
Large infestations can be treated with 100 g/ha metsulfuron(600g/kg) plus 0.25% Pulse® to reduce the density before treating with the more expensive Grazon® mixes.
Individual plants can be controlled by spaying a mixture of 1 part Access® in 60 parts Diesel on the basal 500 mm of each main stem.
Seedling and small plants can be hand pulled. Larger plants tend to break off and regrow. Burn material from manual control on site, if possible, to reduce the risk of spreading seed.
Replant species that will provide complete shade as quickly as possible.
Avoid removing soil from areas that are, or have been, infested with Gorse.

Herbicide resistance:

Biological Control:

A number of biocontrol agents are under investigation or have been released. (1259).
1120 has done an economic analysis of biocontrol of gorse and concludes it would be of net benefit.
1260 has a good review of work before 1977.
94 arthropods feed on gorse and 15 appear host specific (1261).
1262 summarises biocontrol in NSW, 1263 summarises biocontrol in Hawaii up to 1995.
Moth
Anisoplaca ptyoptera moth used in NZ (1264).
Spider mite
Gorse spider mite was released in WA in 2003 and has survived but has had little impact.
Released in Tasmania and Victoria in 1998 (1265).
Gorse spider mite, Tetranychus lintearius, was imported into New Zealand in 1988 (1266).
Stethorus bifidus (Coleoptera: Coccinellidae) preys on gorse spider mite (1267) and can limit its effect on gorse.
Silwet®, glyphosate, triclopyr and triclopyr/picloram were toxic to gorse spider mite (1229).
Seed weevil
Released in NZ in 1931 (1268) but has had little effect (1151).
Gorse seed weevil (Apion ulicis) reduces seed from 4 per pod to 1 per 4 pods but is only effective on the July-December seed production period and has little effect on the autumn seed set (1269, 1270). In NZ it has had limited impact on overall gorse seed production and infestation (1271) even though it can reduce seed production by 45% in some situations (1049).
1272 has a life table.
Seed predation 7-89% in Spain (1273) and 0% in one year and 98% in the next in Chile (1274).
Fungus
Fusarium tumidum is a potential bio-herbicide (1275) but has failed to produce epidemics in experiments so far (1276). Long dew periods are required for good control (1277) and several isolates have been studied for trichothecene production (1278).
1279 and 1280 has reviewed fungi on gorse in NZ and 1281 fungi for mycoherbicides.
Thrips
Released in NZ in 2000 (1282).
Generalist predators appear to slow the spread of gorse thrips and gorse spider mites (1283).
Thrips plus grazing plus ryegrass competition provides better control than any single treatment (1091).
If thrip numbers are limited, release of 100 thrips per site otherwise use 300 per site (1284).
Rainfall washes some thrips from plants and also kills some (1285).
Caterpillars
The larvae of the oecophorid moth, Agonopterix ulicetella, feed on the green foliage of gorse and were released in NZ in 1990 (1286). It occasionally feeds on White lupins (Lupinus albus).
Vertebrates
Wild Hares eat gorse in Western Europe (1287).
Snails
Large numbers of tiny snails are found under gorse in WA.