U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version



Proceedings, 30th Vertebrate Pest Conference (D. M. Woods, Ed.) Paper No. 10. Published December 12, 2022. 4 pp.


U.S. government work


Roof rats cause extensive damage in orchards throughout the world. Integrated Pest Management (IPM) systems are the best option for managing rodents, yet few management systems have been developed and tested to control roof rats in agricultural settings. We initiated a study in 2020 to provide the foundation for an IPM program to manage roof rats in California citrus orchards. Our initial efforts centered on developing effective monitoring strategies for roof rats to determine when management actions are needed, assessing rat movement patterns to determine proper placement of management tools, and conducting initial tests of Goodnature A24 self-resetting traps and elevated bait stations containing 0.005% diphacinone-treated oats. We determined that the use of both tracking tunnels and remote-triggered cameras served as effective monitoring tools for roof rats in citrus orchards, and a smaller 3 × 3 grid placement of these monitoring tools was as effective as a 5 × 5 grid, indicating that substantial material and labor costs could be saved by using the smaller grid size. Placement of the monitoring tools on the ground or up in trees did not influence the effectiveness of this approach. We determined that roof rats exclusively used orchard habitats rather than surrounding fields, so control efforts should be focused in these areas. Roof rats moved substantial distances daily (~170-190 m), but results from bait station trials suggest that spacing of bait stations and traps should be closer together to increase roof rat encounter rates of these devices. Our trial with A24 traps elevated in orchard canopies suggest that there is an advantage to including a platform underneath the trap to increase trap activation. Collectively, this information provides a baseline for future research targeted at developing an effective IPM program for managing roof rats in citrus orchards.