Evaluation of a 2-active ingredient gas cartridge for controlling northern pocket gophers

The efficacy of a four-ingredient (two active and two inert) gas cartridge to control northern pocket gophers in an oat-alfalfa hay field was evaluated. The reformulated rodent gas cartridge was jointly developed by the Denver Wildlife Research Center and Pocatello Supply Depot to replace the currently registered eitht-ingredient gas cartridge. The reformulated cartridge contains sodium nitrate and charcoal as active ingredients, with Fullerʹs earth and borax as inert ingredients. When ignited, the active ingredients produce primarily carbon monoxide. Four test areas (one control and three fumigated) were randomly established with 15 sample plots (each 0·008 ha) on each test area. Active burrow systems were treated: (1) in the sample plots; (2) outside the sample plots but within each test area; and (3) in the buffer zone around each test area. Pocket gopher activity on each plot was determined pre- and post-testing by an open-hole index. Although there was an increase in pocket gopher activity on the control test area and declines of 7·1, 13·3 and 30·8% on the three test areas receiving the gas cartridges, the difference in activity was not statistically different (p = 0·174). The 17·1% mean reduction in pocket gopher activity in the fumigated test areas was substantially below the minimum standard efficacy of 70% established by the U.S. Environmental Protection Agency for fumigants. This result was similar to two previous studies conducted with the original eitht-ingredient gas cartridge for the control of northern pocket gophers.