There are five species of meadow voles found in California. The two that are most economically important are Microtus californicus and Microtus montanus. Meadow vole populations are extremely cyclic, reaching a peak every four to six years. During these periods when the vole population is increasing in numbers, damage to crops like alfalfa, artichokes, potatoes, and sugar beets can occur. The best time to survey for vole activity is before the crop is planted. The grower or farm operator should look for vole activity in grassy borders around the crop or along roadsides and ditch bank areas. Snap-trapping may also be used to confirm the presence of voles. Clean cultivation and weed control on grassy borders adjacent to crops will help reduce potential harborage for voles. A small or localized vole population on a crop border is much easier to control than if the voles become established in the crop. Rodenticide-treated baits are very effective in reducing vole populations. Bait distribution may be done by spot-baiting, placing bait by hand, or by broadcasting, scattering bait over the entire infested area.

The California Department of Food & Agriculture, under an experimental permit, tested sodium cyanide spring-loaded ejector mechanisms for coyote control in Tehama County. These devices were compared to other traditional methods of coyote control to protect sheep from predation. The effectiveness of the devices, as well as their economy of use, could not be determined, as moisture leakage into defective sodium cyanide capsules limited their utility. IT was projected that cost per coyote taken using the devices would have been $68 per coyote, which was a substantial savings as compared to other coyote control methods. The study indicated that coyote control operations can be conducted using the devices without unreasonable adverse effects on the environment. No accidents with the devices occurred during their use by trained staff during the 8-month study. While aerial hunting and ground shooting achieve the most selective means of taking coyotes, the sodium cyanide ejector devices were more selective in taking coyotes than were steel traps. However, the use of steel traps on nontarget wildlife populations was negligible.

Acrolein (Magnicide ®H) is registered in California as an aquatic herbicide. Studies in Alameda and Modoc Counties were conducted to evaluate the field efficacy of acrolein as a ground squirrel burrow fumigant. Applications of acrolein (92%) at 20 ml and 40 ml per burrow were made from a custom built jet gun connected to a hose which ran to a cylinder mounted on a pickup truck. The burrow openings were covered with soil after application. The application rate of 20 ml of acrolein per burrow provided approximately 90% control of ground squirrels. Acrolein applied at 40 ml did not significantly increase efficacy of the treatment.

Acrolein (Magnacide® H) is currently registered in California as an aquatic herbicide. Field tests were conducted to evaluate its efficacy as a ground squirrel burrow fumigant. Treatments consisted of applying either 20 cc or 40 cc of acrolein (92%) per burrow opening with a specially constructed probe connected to a hose which ran to a cylinder mounted on a pickup truck. The burrow opening was plugged at the time of the application. Burrows in the control plot were plugged in the same manner. Dig-outs and open burrows overlooked during the initial application were re-treated the following day. Both rates of acrolein showed a substantial reduction in the ground squirrel population, in excess of 90%, when adjusted for changes in the population in the control plot. The results appear very encouraging with further field testing warranted.