Farmers are well aware that woody weeds can significantly impact the productivity and persistence of pastures long term if infested with woody weeds. Late spring and early summer presents an opportunity to tackle these weeds. Why?

Timing

  • Weeds are actively growing with adequate soil moisture available.
  • Active growth ensures the chemical is absorbed into the vascular system and transported throughout the plant, including the roots.
  • Weeds are generally not stressed by drought, excessive heat, insect damage, or disease.

Product such as Triclopyr Picloram, Clopyralid, Metsulfuron, MCPA750 offer effective solution for managing invasive species, providing targeted long-lasting results when used correctly. Below is a guide to understanding its features, application methods, and considerations for optimal control of spring woody weeds.

Triclopyr Picloram

  • Acts on both foliage and roots
  • Grasses are normally unaffected and establish quickly after treatment
  • Provide rapid brownout of leaves, dry-down of stems and destruction of the root mass to prevent regrowth.
  • Ingredients remain active in the soil and prevent seeds of the target woody plants and secondary weeds from germinating for many months after application (in some cases up to two years). Factors influencing longevity include application rate, soil type, organic matter, temperature, and moisture. Be aware legumes may be effected when sowing the following season.
  • Ensure Triclopyr Picloram penetrates the leaves before rainfall occurs. Applications should only be made when no rain is expected for at least one hour after spraying.

Clopyralid

  • Clopyralid effectively targets as ragwort and thistles while leaving most grasses unharmed, preserving pasture quality.
  • Absorbed by the leaves and roots, translocating through the plant to kill both above-ground growth and the root system, reducing the chance of regrowth.
  • Once the spray has dried, pastures can often be grazed again shortly after application, minimizing downtime for livestock.

Metsulfuron-Methyl

  • Broad spectrum, including stubborn species like blackberry, ragwort and dock.
  • Active on seedling weeds and smaller weeds (up to 4-6 leaf on most weeds).
  • As a systemic herbicide, it is absorbed by the plant and translocated to growing points, providing thorough control of both above-ground and root structures.
  • Will severely damage Annual and Perennial ryegrass
  • Low price per hectare
  • Tolerant grass species – Perennial phalaris, perennial cocksfoot (stands greater than one year old)

MCPA750

  • Very good with regard to protecting existing pasture.
  • Selective in nature, MCPA750 targets weeds without damaging established grasses, ensuring pasture productivity is maintained.
  • Great on small weeds that germinate after spring and summer rain.
  • Visible effects on treated weeds are typically observed within days, providing fast suppression.

Drift Management

  • Avoid spray drift onto desirable plants or soil containing roots of desirable plants.
  • Spray under light, steady breezes that direct the mist away from sensitive plants.
  • Refrain from spraying in still conditions, as mist may drift unpredictably and damage desirable vegetation.
  • Sensitive plants include fruit trees, grape vines, legumes, roses, shade trees etc

Post Spray Management

Allow weeds to remain undisturbed for optimal results. Avoid grazing, cutting for as long as possible to ensure the chemical is fully distributed and provides complete control.

Conclusion

Choosing the right herbicide is crucial for effective woody weed control, as different weeds respond to different chemicals. For instance, triclopyr works well on blackberries on roots and above ground, metsulfuron-methyl targets broad-spectrum woody weeds like lantana and bracken but damages ryegrasses, and clopyralid offers thistle / ragwort control whilst retaining desirable pasture plants.

Systemic herbicides are ideal for deep-rooted weeds, while residual options help prevent regrowth.

Adhering to best practices ensures success—apply correct dosages, use targeted methods, calibrate equipment for consistent coverage. Avoid spraying in adverse weather to reduce drift or runoff. For sustainable results, integrate chemical methods with mechanical, biological, or cultural controls (like keeping dense pasture stands limiting weed establishment), monitor treated areas for effectiveness, and focus on protecting beneficial plants to maintain farm pasture balance.