Rats and mice can cause serious damage to farm machinery put away for the winter unless appropriate preventative measures are taken.
Rodent damage to machinery is a serious issue for many farmers, according to Ken Black, rural hygiene manager at Bayer.
He says: “They’re often so pleased to see the end of harvest machinery is shut away without being cleaned properly and left-over grain can be an attractive food source for rodents.
“This is why Bayer is conducting a rodent damage to farm machinery survey to go out to farmers over the winter to find out the extent of the damage made when machinery is in storage.
“Combines in particular spend a significant amount of time in storage and offer excellent shelter and food sources for rodents, if not cleaned effectively post-harvest.
“As part of their natural behaviour, rats and mice gnaw on anything which is accessible, including cables, hydraulic hoses, control panels and even cab fittings,” adds Mr Black. “However, it’s vital farmers understand the fundamental differences between rat and mouse behaviour to control them effectively.
“Rats are far more predictable, because they are choosy over what they eat. They generally live outdoors in summer and move indoors when temperatures drop in autumn and are much more suspicious of changes to their environment.
“Mice are less predictable, generally appearing in larger numbers. They’re more inquisitive and therefore more prone to gnawing on machinery. They live indoors all year and, in my experience, are more destructive,” he adds.
When it comes to controlling either rats or mice vigilance is key. “Obviously, we would all prefer not to have any rodent issues, but in reality farm buildings offer an easy home. Rats can get into a hole around the size of your thumb; mice the size of a pencil. So, if possible, repair holes in the building which give them an easy way in. Once that is done, check buildings on a weekly basis for activity. Droppings are the easiest way of identifying a presence. Mice urine also gives off a distinctive smell.
“For effective rat control, my advice would be to site bait boxes around key areas as soon as machinery is parked. Bait is not necessary at this time, but having the points in place results in the rats being familiar with them before bait is added. This significantly increases the likelihood of bait take once it is placed,” says Mr Black.
Bait should only be applied when activity has been confirmed. “This is important for two reasons; it reduces the risk of poisoning non-target animals and increases the palatability of the bait when needed. Once activity has been confirmed, use a bait immediately. Be aware, rats in particular will leave ‘food’ unless it’s fresh, so monitor uptake and change the bait every few days where necessary. Rats also hoard food, so make sure blocks are tied down with wire. Otherwise, it may be taken away and not consumed.
“Another option for indoor use is to apply a foam product to known rat runs. A foam doesn’t rely on the animals directly consuming the product, it appeals to their grooming habits, when they clean themselves, and they ingest the bait.”
However, because foam does not allow consumption to be monitored in a way a block does, this makes it more difficult to assess control levels, so it is important to integrate pest management practices. The same precautions need to be applied as with traditional baits, so the risk to non-target animals is reduced.
“Mice, because of their sporadic behavior, require lots of baiting points. In a typical combine shed I would suggest about 20 baiting points for fast and effective control. There are no rules on where to place these, but consider putting bait along, or on top of walls, on beams, girders, and around the machinery as well as at ground level,” says Mr Black.
According to John Deere aftermarket sales manager James Morley, dealers see machines every year with significant damage caused by rat or mice activity, which could mostly be avoided if rodents were managed more effectively on-farm.
“The machine we see the most damage to is the combine harvester. A case in point is a farmer who reported tens of thousands of pounds worth of damage because he had to arrange repairs to gnawed wiring harnesses, and replace all of the cushions and coverings in the cab,” he says.
When considering practical rodent management on farms, there are particular areas to pay attention to, Mr Black says. “The first place to start when placing bait, are the points of the machines which touch the ground, particularly the wheels.
“The time most problems are found is in spring when farmers are starting to get machinery ready for the next season. Obviously, this can also result in delays to fieldwork, which can be incredibly frustrating, especially if it means missing a weather window.
“On a combine the dead space behind the rear axle offers rodents a harbourage and potential nesting point. I would also suggest baiting, the left- and right-hand sides of the feeder housing and the space behind the cab due to the amount of cables in this area.
“Other areas include the sieve to the rear of the combine and monitor boxes on the sieve. Where the returns elevator inspection panel is open, bait should be secured in place to prevent rodents gnawing on the rubber ‘paddles’. It’s also important to pay attention to the cleaning fan access points; the hydraulic controls and wiring on the combine. The hydraulic valve and the roof engine bay, should not be overlooked, due to the amount of connecting pipes and cables.
“And finally, the header drive line may require baiting to protect the cables and belts. This may depend on how the header is stored for the winter period.”
Bayer is currently working to better understand the scale of the issue via a national survey being distributed to farmers around the UK. “We want to know what damage has occurred, how much it has cost, and the further impact it’s had,” says Mr Black. “For example, we’ll find out whether farmers have lost valuable days of harvesting as a result of damage to machinery. This is one of the hidden costs which, as an industry, we need to quantify and understand, in order to work at preventing the issue.”