Seeing large numbers of flies on animals or observing cows kicking in the parlour tend to be the main triggers for applying summer insecticides, but this could be too late for optimum fly control on many farms this year.
According to independent consultant parasitologist Dr Peter Bates, last winter was relatively typical in the UK in that there was unexceptional snowfall and near average temperatures. This means the peak fly season could be earlier with greater numbers of flies around all summer long to attack livestock.
“The one thing that the parasitic fly species have in common is that they all have to survive the winter in one form or another. The number of individuals surviving the winter forms the breeding population for the subsequent spring and summer – and the more that survive, the greater the fly challenge. And with the relatively mild winter we have just had it’s likely that many overwintering fly species will have persisted quite well,” he says.
Consequently, Dr Peter Bates says that pre-empting the fly threat this summer will help reduce fly-borne disease problems later in the season.
“Applying insecticide early in the season will both reduce current fly attack and cut next generation numbers. If you can kill flies early or even stop them feeding on your cattle, you reduce their ability to breed. If a fly doesn’t eat, it doesn’t develop reproductive organs.
“For example, one of the main flies that dairy farmers really have to worry about is the head fly and the culprit known to transmit summer mastitis. It is widespread in the UK and one breeding cycle is enough to produce swarms for the whole summer season,” he says.
“Adult flies emerge in early June and lay eggs from July onwards. The larval stage then acts as an adult reservoir, so if you can reduce the number of adults before they start laying eggs there will be lower fly numbers for the following year. The males actually emerge first, followed by the females – so making sure cattle are well treated with insecticide early enough should take out a large proportion of the local male population in any year.”
MSD Animal Health technical manager John Atkinson points out that seeing flies or midges on or around animals is usually the main trigger for applying insecticides, but significant insect populations can have built up by then. Left untreated, an insignificant early season insect population can become a huge one in just a few weeks. “The main objective is to kill as many insects as possible when the first landing parties arrive on your livestock to feed,” he says.
“As well as treating cattle early, it’s also important to keep on top of the insect problem as we move through the warmer months. A mixture of different fly and midge species threaten most farms with populations peaking at different times and waves of attackers hatch out to trouble herds all season long. Regular applications of BUTOX® SWISH onto cattle will reduce the insect threat. And an early first dose will also help control any biting and sucking lice that have built up on animals over the winter housed period. You also get 8-10 weeks fly and lice protection from a single insecticide application. In addition, aim to reduce potential insect breeding sites and consider housing livestock at dawn and dusk if insects are particularly active,” Mr Atkinson advises.
