As we predicted in previous newsletters the last 6 weeks have seen some very significant worm challenges. With the arrival of rain, suspended larval development was reactivated and very high infective larval challenges occurred which by all accounts caught many farmers out.
Drenching intervals of 4—5 weeks proved to be too long and lambs were carrying significant worm burdens by the time of drenching. Worm challenges, despite regular drenching, have been severe enough to significantly impact on lamb growth rates if the reports we have been receiving are anything to go by.
If this dry summer / autumn weather pattern is something we can expect to deal with in future seasons we probably need to adapt our drenching strategies to combat the worm challenges that arise this season. Four week drenching intervals have proven to be inadequate on many properties. On these properties it may be necessary to use shorter drenching intervals of no more than 3 weeks once rain arrives. Intervals can then be extended once the high larval challenge has passed.
On the other side of the coin, during the dry period larval challenges were generally low and in many cases 4—5 week drench intervals were quite satisfactory.
Following these high worm challenges it is a good idea to implement exit drench strategies with Zolvix or Startect as mentioned in our April Newsletter.
P.S. Worm problems also occurred in lambs grazing Brassica crops, Plantain, Chicory and Lucerne, so don’t automatically assume that these types of feeds are immune from problems.