Adapted from the article “Pocket gopher and ground squirrel management for autumn” by Carolyn DeBuse, former UCCE Farm Adviser, Solano and Yolo Counties, in the October 2012 Sacramento Valley Almond News.
Managing these vertebrate pests 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.
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.
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 winter control 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.
It is important to take control steps in the spring and fall because summer control options are not very effective. Spring baiting does not work because the squirrel diet is mostly fresh vegetation. Summer baits are most effective because the squirrels are eating seeds and nuts. However, summer baiting is difficult near almond orchards because the squirrels may prefer almonds over bait. Also, squirrels can hibernate in the heat, blocking off tunnels and making control impossible. Summer and fall fumigation is not very effective because blocked tunnels and crack soil let fumigant dissipate. During the fall the only method that is effective is trapping. 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.
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. Or visit here for more information on ground squirrel biology, monitoring, control methods and laws and regulations.