Best Practice Rodent Control

Bait uptake is the key

The greatest concern for rodent control programs is behavioural resistance, which is when rats and mice refuse to eat the bait.

Rats are neophobic making them naturally wary of new and unfamiliar objects. They may refuse to eat a new food for up to 10 days and, even then, take only small amounts. This poor bait uptake has been linked to rat survival rates exceeding 50%.

In recent years mice populations have been observed refusing to eat some cereal-based baits because they are unable to digest them.

This type of resistance has placed increasing importance on removing alternative feed sources, improving bait palatability and the diligent maintenance of bait stations to ensure there is enough bait available for all rodents to ingest a lethal dose.

Therefore careful consideration must be given to the placement of baits (and bait stations) to maximise rodenticide uptake.

 

 

A planned approach is best

Before treatment begins, a thorough survey of the infested site is an essential key to success. Make a plan of the site, observed runs, location of droppings, signs of gnawing, burrows, water sources and potential points of entry to buildings. With this site map you will be able plan the positioning of your baiting points.

When surveying the farm it is important you also make a note of any environmental changes that could be made to reduce the attractiveness of the site for rodents after the treatment is completed. Usually this will involve rodent proofing buildings and entrances as well as removing rubbish and weeds that can provide cover. Importantly, the site should not be cleared before the treatment has finished, since this will disturb the rodent population and is likely to reduce bait acceptance.

Before laying baits all food sources should be well secured against rodents and any spilled feed should be removed.

 

 

Bait placement and maintenance

FOR RATS, place bait beside well-defined runs, in and around burrows, holes and other sheltered places, where signs of gnawing, footprints, smears or droppings are present.

• Ensure that there are plenty of bait points. Insufficient bait points are probably the most common cause of failure in a baiting program.
• Cover all bait to encourage rats and mice to feed (rodents prefer cover when feeding). This will also provide protection from rain and help to prevent non-target animals from eating it.
• A rodent needs several feeds over a number of days to build up a lethal dose of anticoagulant bait. Therefore it is essential to regularly examine and top up bait points, especially during the first two weeks of the program.
• Where bait has been completely consumed, increase the amount of bait at that baiting point and continue to bait for a full week after all feeding has ceased at all, baiting points.
• It may take 4-10 days for a rodent to die after ingesting a lethal dose of 2nd generation anticoagulant and therefore it may be two weeks before a decline in the infestation is observed. Rodents will usually return to their burrows or nests before dying, so the dead bodies found around the farm are often not representative of the extent of the infestation.
  Where dead rats and mice are found they should be promptly removed and disposed of according to local regulation.
• At the end of the programme all remaining bait should be removed and disposed of to avoid harm to wildlife and non target species.

FOR MICE, baiting practice is much the same as it is for rats except that a large building may contain a number of different colonies, each of which must be treated as a separate infestation. The quantity of bait per baiting point will be much smaller than for rats. However because of the erratic feeding behaviour of mice many more baiting points are required. Since mice are inquisitive and will readily enter containers, it is convenient to place baits in boxes. Moving these around will also exploit their tendency to explore new objects. Although the initial bait quantity required for mice is small, the amount required to top up bait points may be substantial depending on the level of infestation.

 

 

Protection against re-infestation

To avoid re-infestation – set up barrier baits for a limited period. Monitor every 3-4 weeks, until confident that no bait has been consumed.

Rodent Proofing Tips

• Close all holes and possible points of entry below a height of 90cm
• Make sure that there are no openings greater than 0.6cm around doors and windows
• Ensure feed stores are secure and well maintained
• Keep farm site clear of all rubbish, weeds and other debris
• Fit guards on down pipes and screens on grills and airways
• Fit kicking plates on the bottom of doors to prevent rodents gnawing at the base
• Eliminate vegetation from the exterior of buildings and maintain an uncluttered, vegetation free, perimeter of at least 1m around buildings
• Trim any branches overhanging buildings
• Remove debris that rodents can use for nesting, such as pipes, wood piles, old equipment
• Minimise the availability of water sources (eg stagnant pools, ponds, ditches etc) near to farm buildings