Written By: Carolyn DeBuse, Former UCCE Farm Adviser, Solano and Yolo Counties
Managing gophers and ground squirrels is a year-round task. Gophers can be controlled with most methods throughout the year but squirrel control methods change with the seasons depending on the squirrel biology. This article will outline the control methods but also inform you about some outstanding online resources that are useful to learn new information, understand seasonal cycles, and determine the best control methods to use.
Pocket gophers: Gophers are active all year round and can be controlled with traps, poison baits, fumigation with aluminum phosphide, and a gas explosive device (Rodenator ®). Recent UC research showed that trapping plus additional fumigation had the highest efficacy. The reason that these two methods were combined was because some gophers can become trap shy so additional fumigation killed the individuals that the traps were missing.
Baiting with strychnine came in second for control and the use of the Rodenator® was the least effective. To prevent a re-infestation after reducing the gopher population, destroy the existing tunnels and level the mounds by disking. With non-tillage orchard floor management disking isn’t desirable so it’s even more important to prevent gophers from becoming established in the first place. Keep vegetation away from the tree trunks, especially in young orchards. More information about gopher control can be found at the UC IPM website.
The UCCE Vertebrate Pest Control Education website now has training modules online for gopher, vole and ground squirrel control. Go through the training online or download a podcast that you can listen to anywhere. Find it at: http://ucanr.edu/sites/vpce/.
Ground squirrels: The task of controlling ground squirrels is so difficult and never ending that UC Cooperative Extension has a dedicated webpage just for them. The site contains information on biology, monitoring, control methods and laws and regulations. It should be your first stop for new information and education.
“Ground Squirrels Best Management Practices” is at: http://ucanr.edu/sites/Ground_Squirrel_BMP/.
Ground squirrels are controlled in much the same manner as gophers. They can be controlled with traps poison baits, and fumigation. Different methods work best at different times of the year. During the winter months the squirrels hibernate so there are no effective methods. In spring, fumigation is best because the squirrels are breeding; the burrows become nurseries, and the soil in usually moist holding the fumigant in the burrows.
Baiting does not work in spring because the squirrel’s diet is almost solely fresh vegetation. During summer, baits are most effective because the squirrels have changed their diet over to seed and nut collection. Summer baiting is difficult near almond orchards because the squirrels may ignore the bait preferring almonds instead. In the heat of the summer, squirrels can hibernate in blocked off tunnels and control is not possible. Blocked tunnels and crack soil that lets the fumigant dissipate from tunnels make fumigation a poor choice in summer and fall. So it is important for almond growers to use methods in the spring and fall so that populations don’t get out of hand. During the fall the only method that is effective is trapping. Trapping can also be effective any time of year. Like gopher control, after reducing the population, take measures to destroy the burrows and dens to discourage re-infestations.
With any use of poison baits or fumigant, caution should be taken to use them safely. Follow labels carefully and obtain correct permits from your county agriculture commissioner for the use of restricted poisons. Always take care to protect workers and non-target wildlife.