Summer versus winter drenching - not a recipe decision

摘要

DrenchPlan, the recommended sheep worm control program for central and southern NSW, was first launched in 1985 as a joint venture of CSIRO, NSW Agriculture and Rural Lands Protection Boards (RLPBs). It has undergone various refinements since then and the current version - DrenchPlan 2000 - has increased emphasis on integrated parasite management (IPM). Also, among other things, the program recommends that the second summer drench should not be automatic. Rather, the decision whether or not to drench at this time should be based on results of worm egg counts (WormTesting), with a view to avoiding unnecessary drenching and selection for resistance. Not everyone, however, sees summer drenching as the best option. The proponents of winter drenching in southern NSW sometimes go so far as to say that summer drenching is the cause of all our drench resistance problems. Often the Western Australian (WA) experience is cited as proof of this because the Western Australians practise summer drenching, and they have among the worst resistance problems in Australia, with roughly 40 percent of farms having resistance to the macrocyclic lactone (ML, 'mectin') family of drenches.