- Sheep and goats readily graze broom seedlings which can help reduce establishment of the weed. Intensive grazing of broom seedlings can significantly reduce the number of plants that establish
- The combination of pasture competition, trampling and grazing can severely reduce seedling numbers.
Pasture species/cultivars and fertiliser application
- Maintaining a dense, vigorous pasture will help to prevent broom re-infestation
- Spreading ryegrass and clover with fertiliser can help a pasture to outcompete broom seedlings which establish after burning a mature broom stand.
- Burning reduces broom numbers although plants can re-establish from seedlings in bare areas
- Slashing broom in spring followed by burning in autumn gives more effective control.
- Broom can be ploughed, slashed and pulled with chains towed by bulldozers
- Cutting can be used in combination with herbicides
- Cutting is not always possible as broom can grow on inaccessible hillsides and valleys.
- Chemical control can be used along with cutting for effective control of broom.
ALWAYS READ PRODUCT LABELS BEFORE APPLYING
||When to apply
||When plant in full leaf
||Initially severe but recovery rapid
|triclopyr + picloram
||Spring â€“ early summer
Consult your farm consultant, industry rep or the New Zealand Agrichemical Manual for more information about chemical control.
Several insects have been introduced into New Zealand as biological control agents for broom.
Broom psyllid (Arytainilla spartiophila)
- Native to Europe, this insect was released extensively in the 1990s. Now established at many sites throughout New Zealand, both adults and nymphs suck sap out of new growth in spring
- The insect produces one generation per year with the adult female laying eggs from late spring to early summer. The following spring, nymphs emerge, developing though five stages and becoming adults by late spring
- Adults look similar to aphids. They are 2-3 mm long, pale brown and winged.
- When eggs are laid they are embedded in the stem, protected by a waxy covering
- Manually spreading the psyllid is beneficial as they only disperse slowly. The best way to do this is to collect nymphs from November-October by cutting infested shoots and carefully placing cut material onto uninfested broom bushes
- Care must be taken while doing this as psyllids are fragile and spend most of the year immobile. They are also sensitive to herbicides.
Broom seed beetle (Bruchidius villosus)
- Native to Europe, this beetle was released widely in New Zealand during the 1990s
- As broom pods begin to form the adult female lays eggs. Larvae then develop inside the seeds and new adults are released when pods mature and burst open. One generation is produced per year
- Adults are 2-4 mm long, black and roundish. Eggs are smaller than a pinhead, shiny and are laid close to the edge of the pod
- When larvae emerge they burrow into the soft green seed pods. Pupae develop and are hidden within the seeds
- In spring, adults can easily be seen on flowers as they feed on pollen
- Larvae cause the most damage to the plant as they feed on its seeds. Studies show that this insect is capable of destroying 80-90% of an infested plantâ€™s seeds
- The beetles spread steadily by themselves, although spreading them manually may improve the control of broom
- The easiest way to do this is to harvest and spread infested pods to other plants when they are blackish-brown and beginning to burst open.
Broom twig miner (Leucoptera spartifoliella)
- Native to Europe and accidentally introduced in the 1950s, this moth is now common throughout New Zealand
- Producing one generation per year, adults emerge in early summer, with females laying eggs throughout summer months
- From early autumn to spring larvae feed on stem tissue, emerging to pupate in mid-late spring
- Adults are silvery-white tiny moths (3-4mm). They lay white oval eggs on young stems
- Larvae are translucent. They cause dieback of stems as they feed just under the stem surface. When a large proportion of the plant has been affected bushes grow and flower less. Larvae may also cause the plant to die
- Large scale outbreaks are common in parts of the South Island. The moth continues to spread successfully throughout the rest of New Zealand, causing severe damage.