An Equilibrium Analysis of Antibiotics Use and Replanting Decisions in Apple Production
Roosen, Jutta, Hennessy, David A., Journal of Agricultural and Resource Economics
Antibiotics are used in fruit production to control fire blight, a bacterial disease of fruit trees that causes yield losses and eventually tree death. Fearing the development of widespread antibiotic resistance, scientists and public health officials are becoming increasingly concerned about antibiotics use in agriculture. A framework is developed for assessing the impacts of changes in tree damage risk following a ban on antibiotics use in the apple industry. Allowing for entry and exit, a long-run analysis of replanting dates and equilibrium prices is provided, as well as an estimate of the welfare impacts of a ban on antibiotics.
Key words: antibiotics, apple orchard, dynamics, equilibrium, replanting, resistance
Antibiotics are used in fruit production to control fire blight, an economically important bacterial disease of apples, pears, and other plants of the rose family (rosacea) caused by the bacterium Erwinia amylovora. Fire blight differs from other common plant diseases in that it not only affects yield and quality of the current crop, but also leads to significantly lower tree productivity for several years. Severe infections can lead to tree death, especially in younger trees (van der Zwet and Beer). Outbreaks of fire blight are sporadic, but losses can be severe if the disease diffuses in a given production area.
Currently, 35.8% of U.S. apple acreage is planted to fire blight-susceptible varieties (Rosenberger). This percentage continues to increase because many of the new varieties, such as Fuji and Pink Lady, are much more susceptible than the common older varieties, such as Red or Golden Delicious. Furthermore, a similar trend toward planting rootstocks with high susceptibility to fire blight has been observed (van der Zwet and Beer). Plant pathologists have consistently reported fire blight as a disease of high importance in apple and pear orchards (van der Zwet and Beer).
In 1991, a severe fire blight outbreak in Michigan caused losses estimated at $3.8 million. If antibiotics are unavailable for fire blight control, experts predict apple acreage would decrease by 13% in the next five years, and annual yield would decrease by 8% (Rosenberger). The principal antibiotics in a fire blight control program are streptomycin and oxytetracycline. Copper compounds are available as an alternative means of control; however, they are much less effective and more phytotoxic than antibiotics.
There is a possibility of losing access to antibiotics as a means of disease control in agriculture. This practice is currently a controversial issue due to public health concerns over the risk of resistance development (Witte; Grady). The increase in antibiotic resistance has triggered policy makers' concern, and policies to reduce the nontherapeutic use of antibiotics have been proposed. Bacteria can store their resistance genes in plasmoids, a cell structure which can be transferred between bacteria, thereby also transferring the resistance genes.' It has been shown that people who are frequently exposed to antibiotics are at higher risk for contracting antibiotic-resistant bacteria (Levy 1998). When applying antibiotics in aerosols to fruit trees, bacteria on the trees are killed, but lingering antibiotic residues can encourage the development of resistance.'
These public health concerns seriously challenge the future use of antibiotics for disease control in fruit production. In fact, in Italy antibiotics may no longer be used for fire blight control. Moreover, because of developments in apple production systems themselves, a study of the implications of losing control over fire blight is of particular interest. Specifically, the fire blight bacterium has developed resistance to streptomycin in the Pacific Northwest (Smith). Growers have to rely on access to oxytetracycline, for which an exceptional permission must be obtained from the Environmental Protection Agency. …