Autumn Worm Control

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This autumn, focusing on worm control is crucial especially in the aftermath of rain events.

Here’s why an autumn rain event influences parasite dynamics and why it poses a challenge:

1. Increased Availability of Parasite Larvae:

  • Rain creates a favourable environment for parasite larvae to both hatch and survive. When rain falls after a dry period, it can lead to a synchronised hatch of parasite eggs and emergence of larvae.

  • Moisture helps larvae survive on pasture, which increases their numbers.

2. Delayed Sugar Re-establishment in Grass:

  • Sugar levels in pasture can take a couple of weeks to re-establish after a rain event. During this time, grass is less nutritious. Reduced pasture quality can lead to increased grazing time, exposing stock to higher parasite loads as they ingest contaminated pasture.

Key worm control strategies:

1. Oral Drenching: Lambs, hoggets, 2-tooths, and lighter mixed-age ewes are particularly vulnerable to heavy parasite infections as their immune systems are still developing or they have lower immunity. It’s essential to keep the drench interval on a regular schedule—every 28 days. Do not let the interval extend beyond 5 weeks, as that can lead to ineffective control.

2. Persistent-Acting Drenches: If the worm burden has escalated quickly and pastures are heavily contaminated, using a persistent-acting drench can be a good option to help manage a severe prolonged pasture larval challenge.

3. Novel Active Drenches: To clean out any resistant parasites use a knockout novel active drench on lambs or hoggets during the March-May period. Options like Zolvix Plus and Startect are highly effective in managing resistant parasites.

4. Targeted drenching of Light 2 Tooths/Ewes Pre Tup: If drench resistance has been diagnosed on the farm, consider using novel drenches, Startect or Zolvix are good options. If drench resistance is not an issue, then an effective combination drench can be used.

5. Grazing management: Grazing adult cattle behind lambs or ewes, or having ewes follow calves, can be a great strategy for maintaining lower parasite burdens. This helps manage the overall worm population on pastures.

These combined approaches will help manage the parasite burden effectively during a potentially “wormy autumn.”