The June and early July rains look set to fuel a fly explosion in
many regions of the country. With conditions so wet and warm, fly
breeding grounds have been plentiful and farmers need to prepare
for an onslaught on their livestock.
“Many of the flies that plague cattle and sheep have
aquatic larvae and warm, wet weather only helps increase their breeding
success,” says applied biologist Professor Richard Wall from
the University of Bristol.
“Moisture allows them to build greater fly numbers either later
this summer or next season depending on the species. And the incidence
of blowfly strike usually soars when summer weather is warm and wet,” he
Horse flies, black flies, common cleggs and midges all lay their
eggs in and around water. Horse flies lay eggs in damp or wet sites
and when the adults emerge they are very aggressive blood feeders.
They deliver a painful bite that can easily disrupt livestock feeding
behaviour. Black flies prefer fast-running streams and rivers but
are also voracious blood feeders, sometimes causing allergic reactions
Common cleggs and midges (Culicoides spp) also feed on blood. Cleggs
are often found on the legs of cattle, while midges bite and suck
blood early in the morning or late afternoon.
“The rains many areas of the UK experienced last month will
undoubtedly increase fly populations, particularly if it stays warm.
Livestock farmers need to be vigilant for the remainder of the summer,” Professor
Schering-Plough Animal Health livestock veterinary adviser Paul Williams
MRCVS says that because of the recent weather farmers need to seriously
consider re-treating cattle now with a proven insecticide.
“With the extreme rainfall we have had recently – and
the conditions now being so ripe for fly breeding – farmers
should consider re-applying deltamethrin insecticides such as Coopers
“Coopers Spot On is rainfast, meaning it won’t wash off
cattle at pasture so easily. Its oil-based carrier also helps the
deltamethrin spread quickly over the whole body. Studies show flies
being killed on the head, belly, legs and rump within two hours of
a single 10ml spot being applied to the back of the animal,” he
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