Fleabanes plants grow rapidly and produce a large number of seeds. Mature Fleabane plants are difficult to control with herbicides. An integrated approach will give the best chance to control these weeds.
- Monitor areas early during the germination period
- Spray weeds when they are a small rosette and before stem elongation starts
- Consider using an adjuvant to improve herbicide uptake
- Moisture stressed plants are much more difficult to control with herbicides
- Rotate herbicide mode of action groups
- Control plants in surrounding areas so they don’t flower and act as a source of seed to infest turf sites. Managing the soil seed bank is critical for long term Fleabane management
Research in cropping situations has clearly demonstrated that the use of herbicides on young plants gives the best control. In an experiment with 9 different herbicide treatments the control of 1 month old weeds was 92%, on 3 month old weeds this fell to 72%.
In Australia seven Fleabane species have become naturalised. In turf situations there are two main Fleabanes which cause problems. These are Flaxleaf fleabane (Conyza bonariensis) and Tall Fleabane (Conyza sumatrensis).
Both species start as a rosette of leaves. With Flaxleaf Fleabane the leaves of the rosette are lobed. The leaves of Tall Fleabane on the other hand are toothed but not lobed.
Flaxleaf fleabane can grow up to 1m in height and produces multiple branching from its main stem. The branches often end up being taller than the main stem. The stems and leaves are hairy, which can influence herbicide coverage and uptake. The leaves along the stems are toothed and have wavy margins.
Tall fleabane can grow up to 2m and has a single stem with short side branches. The leaves along the stem are also toothed but do not have a wavy margin. Both species produce fluffy, pale seedheads.
The optimal germination for Flaxleaf Fleabane germination occurs at 20-25oC from seeds in the top 1cm of soil. When this germinations occurs in autumn the above ground growth is slow, but at the same time significant root growth occurs.
In turf situations regular mowing can keep above ground parts fairly small, but when we examine what is happening under the ground we find a very robust root system. This large root system makes control with herbicides more difficult.
A weed that appears small on the surface can hide a large root system which makes control difficult.
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