This is a relatively rare occurrence at Stratford, which with its cooler summer nights is much less likely to experience the two-four continuous days of 12C-plus night-time temperatures required for the build-up of eczema spores.
Surprisingly, this rarity itself, coupled with our past experiences at the Demonstration Farm, provides some insights into the reliability and application of FE warning systems.
The main problem with FE warnings is the great variation in spore build-ups between farms, districts and seasons. In the old days of the MAF FE Warning Committees we used to reckon that the Stratford area would experience dangerous spore levels, with consequent outbreaks, about one year in 10. Symptomatic of this was the fairly commonly held belief that “You don’t get facial eczema at Stratford”.
The common result of this belief was widespread criticism. In most years the committee was being too alarmist, and in the rare bad year it was derelict in its duty for not issuing sufficiently accurate and creditable warnings.
The inevitable result was in the years immediately following an outbreak awareness was high and precautionary actions more common. However, with the passage of time, and no discernable risk, complacency returned, to most likely reach its highest level when the next one-year-in-10 – or whatever – happened, with the whole cycle repeating itself.
In the days when MAF operated FE Warning Committees the Demonstration Farm was an obvious site for spore monitoring.
If it produced spore levels at all, they seldom rose above the 5000 mark – well within safety limits. However, in one of our one-in-10 years, when spore counts throughout the district generally showed critical increases, the Demonstration Farm site didn’t. It showed its usual about-5000 level, so no worries.
‘If that sort of variation happened on one farm what would it be like over the whole district?’
However, to the manager’s chagrin a few cows started kicking off cups, searching for shade and exhibiting all the other usual symptoms. Because the outbreak didn’t match the spore levels recorded, the first step in investigating the problem was to check spore levels on every paddock on the farm.
That first step was the only one required, because, in a classic example of Murphy’s* Law the paddock with the monitoring site was the lowest on the farm at 5000/gm pasture. From there the spore counts ranged upwards to a phenomenal high of 500,000. It was no wonder FE symptoms were showing up.
The real lesson to be learned was the enormous range was happening on one farm, and the paddocks on that farm were fairly homogeneous. If that sort of variation happened on one farm what would it be like over the whole district?
The message must surely be that district spore levels can be a very poor indicator of the FE risk level on any individual farm and should not be used as such.
That’s not to say district spore counts are useless. They are valuable in giving a broad picture of the status of the whole district. The more samples taken, the more reliable the average will be.
More importantly, district spore counts can very usefully provide the degree and rate of change in spore counts. When they are rapidly on the rise, warning bells must start ringing.
The best strategy is to tie the district information into the past history of the farm. Data recorded on the farm like rainfall, grass minimum temperatures, and better still, spore counts, can be useful in correlating to the district situation, always remembering single-site data is extremely unreliable in risk assessment.
The overall guiding factor has to be if the farm has experienced FE in the past it can do so again – and unfortunately that is still not definitive because in this age of climate change there is always a first time.
The philosophy of hope for the best and plan for the worst can be very usefully applied to FE prevention.
* Surprisingly Murphy’s Law was not actually written by Murphy, but rather by a fella with the same name.
