Pest control hub
What does it look like?
Ragwort is a member of the daisy family. It is an erect, annual to perennial herb and usually grows to 45-70cm tall, but can reach 1.6 metres. It has reddish-purple stems and wrinkled, divided leaves, which are dark green on top with a downy lining. Leaves appear in a rosette that grows into a dense cluster. Its flowers are bright yellow, and appear in clusters. Downy (fluffy), parachute-like seeds are present.
Ragwort prefers areas of open space with some area of bare ground for seeds to germinate in, particularly in high rainfall areas. It will invade open forests, riverbeds, swamps, pastures and coastal areas. It also tolerates a wide range of environmental conditions, except for shade. Especially abundant in areas of higher rainfall. A well known pest on dairy farms, densities of this species have steadily declined in Northland since the introduction of a boiological control, the flea beetle. As such, this species is no longer a significant threat on most properties.
Why is it a problem?
An aggressive, prolific flowering plant that colonises exposed areas, i.e. paddocks. Matures quickly, may reduce the productivity of the land, also may out-compete native plant seedlings.
The ragwort flea beetle (Longitarsus jacobaeae) has established well throughout Northland. Many areas that have not been regularly sprayed, have very low numbers of ragwort now. Information on this beetle and how to find it on your ragwort can be found at Landcare Research
The best advice for long term control of ragwort is to not to spray or control ragwort at all. Landowners are encouraged to wait for the numbers of flea beetle and ragwort to be in balance, this can take 7 - 10 years, then there will be a few ragwort plants around to support an ongoing population of flea beetles.
If you feel you must use some control, winter months (July to August) is the safest time to control ragwort as larvae are pupating. However be aware that the less food available, the less beetles will survive for the following season.
- Spray seedling rosette plants (winter / early spring only): 2,4-D (50ml/10 litres (knapsack) or 1-3 litres/ha in 300 litres water (boom spraying) This will severely disrupt the population of biocontrol insects and unless thorough control follow-up is carried out it is likely that the ragwort issue will get worse. This will not control regrowth of plants.
- Spot spray rosettes or mature plants with metsulfuron (1g /10L) This product will not kill the mature beetles and won’t disrupt the biocontrol population as much.
- Spot spray with Tordon PastureBoss or similar (60ml /10 L Knapsack 200-300ml/100L water) This will severely disrupt the population of biocontrol insects.
- Granules (winter / spring): apply Tordon 2G (2g/plant - a half level teaspoon) to the centre of each plant. Ideally crush the plant first.
CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.