|Botanical Name||Ageratina riparia|
|Origin||Mexico, West Indies|
DescriptionErect or sprawling herb to shrub, 0.3-1 m tall or taller. Stems clothed in purple-striped hairs. Stems often tinged purple. Leaves opposite, narrow elliptic (rounded at both ends and wider in middle) to lanceolate, to around 100 mm long. White flowers in dense heads, Aug-Jan-(Mar).
Where is it found?Plant communities within forest river systems. Slips, open rocklands, freshwater wetlands, steepland forest, damp forest areas including coastal, alluvial forests, forest light gaps, roadsides, quarries, exotic plantations and wastelands.
Why is it a problem?Capacity to completely smother existing communities that are less than about 1 metre tall, with dense persistent mats of semi-woody stems, often with no regeneration at all beneath them. Also causes more rapid build-up of sediment, especially on alluvial flats, creates less stability of steepland gullies and streams when compared to Blechnum capense and manaku. Hebe acutifolia, Pratia spp. and other specialised streamside plants are species likely to be heavily impacted. Is a major threat to open streamsides even in unmodified forest.
How does it spread?Typical dispersal routes are streams and roadsides as well as forest gap to forest gap. Plant is spread by wind, water and probably road mowing machines. Disturbance caused by flooding of streams opens up habitats and distributes seed.
How do I get rid of it?
Physical control is ineffective as even very small pieces of root regrow.
Allow sprayed vegetation to rot. Compost or burn dug out plants.
Spray with Metsulfuron or Glyphosate.
(i) Metsulfuron + Penetrant. Spray when not flowering and follow up in 2-6 months.
Rate - Handgun 10 gms Metsulfuron + 100 mls Penetrant/100 litres water (spring - mid-summer). Handgun 15 g Metsulfuron + 100 ml Penetrant/100 litres water (winter). Knapsack 2 g Metsulfuron + 10 ml Penetrant/10 litres water.
(ii) Glyphosate + Penetrant. Avoid summer dormancy.
Rate - Handgun 1 litre Glyphosate + 200 ml Penetrant/100 litres water. Knapsack 100 mls Glyphosate + 20 ml Penetrant/10 litres water.
Some re- growth will occur with Glyphosate.
|Two biological control agents have been introduced. Mist flower gall fly (Procecidochares alani) and White smut fungus (Emtyloma ageratinae)|
Tackle small infestations first. Work within isolated areas e.g. an arm of a river. Work from upstream areas before downstream. Tackle initial knockdown in autumn. Follow up to achieve 100% coverage when in flower (July-August). Repeat process annually until there is no longer evidence of the plant's growth. Metsulfuron is more effective than Glyphosate.
For further information and more detailed chemical control methods please refer to Bay of Plenty Regional Council's Fact Sheet on Mistflower.
This plant is prohibited from propagation, sale and distribution within the Bay of Plenty Region!