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Mouse and Rat Control

An integrated pest control system consists of:

  • Identify the problem areas by inspection
  • Identify the food source
  • Choosing a bait with the food source in mind
  • Choosing the right placement of the bait
  • Commence bating

When rodent signs are found or rodents are seen, check the area for their food source, for moisture conditions and where to place the bait. The placement of the bait is very important, for it must be placed as close to the runs or paths as possible. For example, with landfills place bait in the garbage where the activity is.

A common complaint is that the bait is no good. But the bait was in front of the granary when the rats were under the pile of old posts and junk behind the bin. Therefore place the bait where the rats are. Baits come in various forms and choices must always be made according to moisture conditions and the food source.

There are six basic types:

  1. Meal or Cereal baits are the most palatable, but they readily take on moisture. Think of it as starting a fire with kindling
  2. Pelleted baits are more weather resistant and tend to overcome some of the taste aversions associated with some active ingredients. Rodents will carry the pellets to a storage place for later use when their regular food source is gone. As for moisture, it’s like starting a fire without splitting the log.
  3. Whole Grain baits have a fair resistance to moisture and work well as they most closely match the food source in this province.
  4. Parraffinized baits are ideal for high moisture areas. Some have a very high wax content and are not affected by water so they remain palatable for a long time. These baits, however, have a slower knockdown rate. Now it's like trying to start a fire with a wet log.
  5. Powdered baits have no resistance to moisture. It's like lighting a fire with gas.
  6. Water baits can be very effective. Rodents take water from unfamiliar sources before they will take dry food. But you need to get water from the same source as the rodents are drinking.

Remember to keep bait fresh since rodents are finicky; they will not take mouldy, rancid, contaminated, or especially insect ridden baits. Even though the same active ingredient is found in more than one brand, at each site rodents prefer some products to others based on what the food source is.

The ideal rodenticide should have the following properties:

  • The stuff has to work. Many products have a problem with taste, and no one product is the best at very location. A good practice is to provide several baits to determine which is most effective at each site.
  • It should be selective to rodents, for it gives a margin of safety. The product should be a low hazard to non-target animals. There should be no plant uptake either.
  • The formulation needs to be less attractive to non-target animals. Grain based baits are not very attractive to dogs and cats. On the other hand, pellet baits are like pet foods. Rodents easily carry pellets to unprotected places.
  • Ideally there should be no resistance to the product. But rodents keep ahead of this.
  • Painless action is an ideal property in rodenticides.
  • The rodenticide needs to quickly breakdown in the environment because rodents are at the top of the food chain. The length of time it takes for a rodenticide to be broken down directly effects the length of time non-target animals have to be treated when they consume bait. No residual effect is desirable. i.e. – Warfarin – 7 to 10 days, Bromadiolone – 30 days,
  • There needs to be an antidote.
  • Products need to be economical in use.

First Generation Baits – multiple feeding

  1. Warfarin has the longest history of use. An inherited anticoagulant resistance has developed because it’s been used for so many years. Warfarin baits are mixed at 0.05 or 500 ppm of the active ingredient. Its biggest drawback is that the rodents must eat the bait for several days to consume enough to kill them. When other food is available, they may not consume enough.
  2. Chloraphacinone baits have the same drawbacks as Warfarin in that it is hard to get a lethal consumption rate. It has not been covered in university studies.
  3. Diphacinone is from a different chemical family that kills in 4-7 days with a lethal consumption. It has been around for 50 years and is estimated to be about 60 times stronger than Warfarin. These baits are the most cost effective to use in some formulations. But the amount required to produce dead in parraffinized products is quite high, and rats don’t see a wax block as a food source.

Second Generation Baits – single feeding

Rodents have shown a definite aversion to some of these baits because they taste the active ingredient in them and shy away.

  1. Bromadiolone has a minimal taste aversion so the bait does not have a lot of flavour added. A lethal dose produces a high fever, so the rodent stops eating and dies in 5-7 days. Rats usually die in their runs.
  2. Brodifacoum has high taste aversion so the baits have as many as 16 different flavours added. It's the strongest anticoagulant on the market but has no side effects. The rodents continue to eat which leads to a high consumption rate and a high cost. Rats suddenly die from massive internal haemorrhaging in 4-10 days. Dead rats are found lying all over so it is the most visible of all the baits. Because it is flavoured, a percentage of the rodent population does not like it and tend to store it.
  3. Bromethalin is one of the newer products. It is a nerve toxin, not an anticoagulant. The actual amount required to kill is about 87% less than Brodifacoum, making it cost effective. There is no antidote and a sub-lethal dose produces permanent brain damage.
  4. Difethialone is the newest product. It is a single feeding and highly toxic, so it can be mixed at half the rate, 25ppm, of the others. Therefore there is less taste aversion to the active ingredient. These baits have a peanut aroma which some rats like. Those who don't store it.
  5. Cholecalciferol is the only one for use with organic producers. It is not an anticoagulant but a vitamin D3 concentrate with no real antidote. It produces a high calcium level in the organs of the body, so there must be a constant fresh supply. Remove as much of the food source as possible; if the bait is diluted it will only produce healthier rodents.

Using and Placing Different Baits

Always remember that one kind of bait will not do a perfect job at every location. The use of the same combination of baits over an extended period of time tends to lead to bait aversion. Always remember that the first 90% of the population in a colony doesn’t matter. If you don't get the last 10%, they will be back to 100% in a couple of months.

Conclusion:

  • Remember the food source when choosing bait.
  • Meal baits cannot be moved but have a short life.
  • Pellet baits can be moved but have a longer life.
  • Parraffinized baits have the longest life but have a slower knockdown rate.
  • Liquid baits work well in dry conditions.
  • The last 2% are the ones you are after!

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