Economics of Plant Disease Outbreaks

ncreasing trade liberalisation, globalisation and international transportation of people and commodities have increased the potential for disease incursion, both plant and animal, in countries like Australia. While a comparatively strict quarantine regime and geographic isolation provide substantial protection in Australia, disease incursions are not uncommon. In recent years, there have been several exotic disease outbreaks including wheat stripe rust, bacterial blight of cotton, sugar cane ratoon stunt, potato cyst nematodes, karnal bunt, grapevine leaf rust, papaya fruit fly, Newcastle disease in poultry flocks, and Ovine Johne’s Disease (OJD) in sheep. Recent attention on the incursion of plant diseases followed the outbreak of black sigatoka, a banana leaf disease, in the Tully district of North Queensland in 2001, and citrus canker, a highly contagious bacterial disease for citrus fruits, in the Central Highlands region of Queensland in 2004. An outbreak of any pest or disease, either plant or animal, has the potential to be widespread in countries like Australia, with subsequent economic, social and environmental impacts. At the same time, the trade liberalisation process is focused on avoiding quarantine being used as a trade barrier, where the risks of disease incursion are used to ‘trump’ any potential benefits of increased trade flows. There is a strong economic case for an efficient quarantine regime, with import, monitoring and surveillance procedures, and for appropriate eradication measures when disease outbreaks occur. Estimates of the economic cost of outbreaks, and the benefits of avoiding them, are needed to help weigh policy options about appropriate future prevention and response strategies. A number of studies have been conducted on the entomology and epidemiology of introduced diseases (for example, Gottwald, Graham and Schubert, 2002). However, little research attention has been paid to the economics of such outbreaks (Hanold, 1996). In Australia, there has been work in recent years in the area of weed management which is analogous to the disease problem in terms of containment options and timing. A review is provided in the next section. Although public policy evaluation and administration of plant disease incursion issues are considered to be important, they remain understudied. The full extent of the costs of damages caused by pest and disease incursions has only recently received greater attention (Evans, 2003). There is only a limited number of studies attempting to quantify the economic losses of plant disease outbreaks and the desirability of appropriate response strategies. To estimate the economic cost of an outbreak, proper identification of losses incurred and their quantification are important. Costs of an outbreak can be