Preparing your barn for winter - Pest management series part three

Elizabeth Ferry<franzeli@msu.edu> and Casey Zangaro<zangaroc@msu.edu>, Michigan State University Extension - October 01, 2018

This 4-part series will address different areas of pest management and assist farmers with building and maintaining a pest management plan that is feasible for their options.

Mouse trap sitting on concrete that is loaded with peanut butter.

Rodent Control

Rodent control on farms and around livestock facilities should be a multi-pronged approach as there is no exact method that is 100 percent effective. Due to the make-up of farms and the availability of feed and materials, farm sites are high-risk areas for rodent populations. A solid rodent control plan includes the use of physical and biological methods to remove rodent populations. Physical methods, such as traps are an effective and humane way of getting rid of small populations of rodents either inside or around the perimeter of the barn. There are different types of traps that can be used for pest control. Snap traps or break-back traps are very common rodent control methods. The most effective way to lure rats or mice into these traps is to use food and leave the trap alone near a wall or door for four to five days. Glue boards are also very effective and are used in a similar way as the trap. However, the use can be severely decreased by dust being captured on the glue and not allowing the rodent to be trapped. This method also can be seen as inhumane by different groups. Sound devices, usually ultrasonic, are effective in causing rodents to leave the premises without catching them. Physical methods are best when used to help control a rodent population and to deter infestation, however, many times the effectiveness of these methods are debatable and depend on the creativity of the user.

A second method to control rodents and the best method to use when dealing with an infestation is the use of rodenticides. Rodenticides are basically pesticides used to kill rodents, these products must be proven substantially effective by those that sell/produce them and the efficacy data for the products must be available to the user. There are two types of rodenticides, anticoagulants and non-anticoagulants, also known as first and second generation anticoagulants. Anticoagulants are used in 90 percent of all rodent baits with the most popular chemicals used being bordifacoum, bromadiolone and difethialone. The most used non-anticoagulants are bromethalin, cholecalciferol and zinc phosphide. It is important to know that Vitamin K₁ acts as an antidote to anticoagulants. The use of rodenticides alone does not guarantee the eradication of a rodent infestation. Many times, population numbers can quickly recover if secondary methods and subsequent treatments are not applied.

First generation anticoagulants like Warfarin and Pindone are less toxic and less persistent in animal tissues. Using this type of rodenticide has a lower risk to human hazard and non-targeted animals. These products can take longer to control rat populations and surplus bait should be available for the rats to feed on. It is important to note that resistance to first generation anticoagulants is widespread in mice. Second generation anticoagulants are considerably more toxic and have a longer half-life. These products have a greater risk to non-targeted animals when ingested and require considerable less bait to be consumed by the rodents to be effective. Second generational anticoagulants are highly effective when you are dealing with a rodent infestation.

Table 2. U.S. Rodenticides Commercially Available
Compound	Classification	Trade Names	Applied Form
Warfarin	1^st generation anticoagulant	Various	Meal, Water
Pindone	1^st generation anticoagulant	Pival^TM Pivalyn^TM	Meal. Water
Diphacinone	1^st generation anticoagulant	Ramik^TM Rampage^TM Tomcat^TM	Blocks Blocks Liquid
Cholorphacinone	2^nd generation anticoagulant	Rozol^TM	Pellets
Brodifocoum	2^nd generation anticoagulant	Havoc^TM Jaguar^TM	Blocks and Pellets Blocks
Bromadialone	2^nd generation anticoagulant	Boothill^TM Hawk^TM	Blocks Meal and Blocks
Difethialone	2^nd generation anticoagulant	Hombre^TM Fast Draw^TM	Blocks Soft bait
Difenacoum	Non-anticoagulant CNS toxin	DiKill^TM	Blocks and Pellets
Bromethalin	2^nd generation anticoagulant	Cy-Kil^TM Rampage^TM Gunslinger^TM	Blocks and Pellets Blocks Blocks and Pellets
Cholecalciferol	Non-anticoagulant vitamin D3	Agrid₃^TM	Blocks and Pellets
Zinc Phosphide	Non-anticoagulant phosphine toxicity	Eraze^TM	Pellets
Table adapted from Timm, 2010

The active ingredients in rodenticides vary from product-to-product and can be classified in three different ways: acute, sub-acute and chronic. Acute rodenticides are fast acting and normally are effective within 24 hours. If a non-lethal dose of acute rodenticides is consumed, rodents can have bait shyness and not consume any more of the bait. Sub-acute rodenticides cause death after several days. The lethal dose of the rodenticide may be consumed early on and feeding of this bait may continue until death. Chronic rodenticides are slow acting and cause death as early as two to three days or on average from five to seven days. Understanding what ways you will be using rodenticides, preventing, control or eradication, will help you decide what product best fits your need.

Along with the variation of active ingredients and classification of rodenticides, there are different types of bait formations. Bait products are found in the form of meals, cut or whole grain, pellets, wax blocks, edible lards/pastes/gels, contact gels or foams and gases. Particulate baits are generally more palatable to rodents when compared to wax blocks, whereas wax blocks are better in adverse conditions and areas like sewers and drainage pipes. Depending on what type of rodent you are dealing with, it may dictate what bait formation you choose. When baiting outside, like in burrows, grains are less likely to be moved or kicked out by the rodents. Care should be taken to cover baits or secure them so that the rodents are less likely to remove them.

Additional articles in series

Part one - Introduction to pest management

Part two - Understanding rodent types and signs of infestation

Part four - Pest control records and monitoring

References

Buckle, Alan, et al. “Anticoagulant Resistance in the Norway Rat and Guidelines for the Management of Resistant Rat Infestations in the UK.” Rodenticide Resistant Action Group, June 2010, www.pestmagazine.co.uk/media/246897/management-of-resistant-norway-rat-infestations-in-the-uk-rrag-june-2010.pdf.

“Rodent Control on Farms.” The Pig Site, 19 Feb. 2015, www.thepigsite.com/articles/4911/rodent-control-on-farms/.

Timm, Robert M. “Controlling Rats and Mice in Swine Facilities.” EXtension, 20 Apr. 2010, articles.extension.org/pages/27261/controlling-rats-and-mice-in-swine-facilities.