Some International Approaches to Rat Control

A computer model calculates the dollar loss due to the presence of plains pocket gophers ( Geomvs buCsarius majusculus) in alfalfa fields. Five alternative control methods are then evaluated. Total cost, cost per acre, hours of labor, and economic feasibility are printed for each control method. The model serves not only as an immediate decision aid but also serves to simulate conditions that likely might occur in the future which in turn could influence current decisions on control of pocket gophers. The purpose of this report is to describe the use of a computer model as an aid in deciding whether to control pocket gophers and what control method to employ. The computer analysis can be run with minimal knowledge of pocket gopher damage or control measures. Basically the analysis compares the dollar loss of alfalfa production, due to the presence of pocket gophers, to the cost of reducing the gopher population. We feel this analysis is important for informing the producer of the magnitude of the economic impact of pocket gophers in addition to establishing an economic threshold for various control strategies. The intent of this paper is not to report a detailed documentation of the model but to demonstrate its application. Nonetheless there are several caveats and assumptions germane to the model and its use which are as follows: f no assessment was made of cultural methods such as crop rotation or use of alternative varieties of alfalfa. a alfalfa loss due to the presence of pocket gophers was estimated for dryland alfalfa and the plains pocket gopher. Losses in other forages or irrigated alfalfa or due to other species or subspecies of pocket gophers may be different. a we assumed forage yields were restored during the season of control. This is certainly not true, but they may be restored by 60% if control occurs during the spring. we assumed control measures would need to be repeated every 3 years. costs of mechanical equipment malfunction or failure or slowing of harvesting machinery caused by gopher mounds are not assessed. PROGRAM OPTIONS The options and format of the model are summarized in a flow chart (Fig. 1). The user must input the number of acres infested by pocket gophers, the value of the alfalfa to the producer (dollars/ton), and the expected yield with pocket