An assessment of the benefits of yellow Sigatoka (Mycosphaerella musicola) control in the Queensland Northern Banana Pest Quarantine Area

The banana leaf spotting disease yellow Sigatoka is established and actively controlled in Australia through intensive chemical treatments and diseased leaf removal. In the State of Queensland, the State government imposes standards for de-leafing to minimise the risk of the disease spreading in 6 banana pest quarantine areas. Of these, the Northern Banana Pest Quarantine Area is the most significant in terms of banana production. Previous regulations imposed obligations on owners of banana plants within this area to remove leaves from plants with visible spotting on more than 15 per cent of any leaf during the wet season. Recently, this leaf disease threshold has been lowered to 5 per cent. In this paper we examine the likely impact this more-costly regulation will have on the spread of the disease. We estimate that the average net benefit of reducing the diseased leaf threshold is only likely to be $1.4 million per year over the next 30 years, expressed as the annualised present value of tightened regulation. This result varies substantially when the timeframe of the analysis is changed, with shorter time frames indicating poorer net returns from the change in protocols. Overall, the benefit of the regulation change is likely to be minor

Predicted economic impact of black Sigatoka on the Australian banana industry

While Australia has lifted its outright ban on banana imports, very strict pre-entry requirements remain in place making it prohibitively expensive for foreign suppliers to land product in Australia. These include the establishment and maintenance of areas of low pest prevalence (following guidelines described in FAO, 2005; FAO, 2007, respectively), trash minimization procedures and post-harvest fungicide treatments (Biosecurity Australia, 2008). Strict though these import requirements are and small the risk of exotic disease transference may be, the potential consequences of some disease outbreaks to the Australian banana industry is potentially huge. In this paper we provide quantitative estimates of these potential damages (in Australian dollars, A$) and discuss the implications for Australia's import risk assessment process using the example of black Sigatoka. In 2001 this disease was detected in the Tully region of Queensland, a major banana production region. The cause of the outbreak remains unknown (Molina et al., 2005), but it was detected early enough to be eradicated at a cost A$17 million (Sosnowski et al., 2009). This outbreak has failed to quell calls to relax banana import requirements further, and criticism continues to be directed at Australia's import risk assessment process and its associated appropriate level of protection (Javelosa and Schmitz, 2006; Leroux and Maclaren, 2011). This is a locus of disease arrival probabilities and outbreak consequences with a unique product which forms a maximum expected damage a product entering the country can pose before violating Australian quarantine regulations. However, in practice the appropriate level of protection is not stated in quantitative terms, but is instead defined in rather ambiguous qualitative terms as very low. Our analysis provides quantitative evidence suggesting that in the case of banana imports, the appropriate level of protection corresponds to an expected damage of A$60 million per annum. This suggests that although current quarantine regulations are trade-restrictive, the appropriate level of protection corresponds to a relatively severe level of damage. (C) 2013 Elsevier Ltd. All rights reserved

Predicting the benefits of banana bunchy top virus exclusion from commercial plantations in Australia

Benefit cost analysis is a tried and tested analytical framework that can clearly communicate likely net changes in producer welfare from investment decisions to diverse stakeholder audiences. However, in a plant biosecurity context, it is often difficult to predict policy benefits over time due to complex biophysical interactions between invasive species, their hosts, and the environment. In this paper, we demonstrate how a break-even style benefit cost analysis remains highly relevant to biosecurity decision-makers using the example of banana bunchy top virus, a plant pathogen targeted for eradication from banana growing regions of Australia. We develop an analytical approach using a stratified diffusion spread model to simulate the likely benefits of exclusion of this virus from commercial banana plantations over time relative to a nil management scenario in which no surveillance or containment activities take place. Using Monte Carlo simulation to generate a range of possible future incursion scenarios, we predict the exclusion benefits of the disease will avoid Aus$15.9- 27.0 million in annual losses for the banana industry. For these exclusion benefits to be reduced to zero would require a bunchy top re-establishment event in commercial banana plantations three years in every four. Sensitivity analysis indicates that exclusion benefits can be greatly enhanced through improvements in disease surveillance and incursion response

Expected annual benefit of a BBTV exclusion policy.

<p>Expected annual benefit of a BBTV exclusion policy.</p

Sensitivity analysis.

<p>Sensitivity analysis.</p

Australian banana production statistics by region.

a<p>ABS <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042391#pone.0042391-ABS1" target="_blank">[6]</a>.</p>b<p>Australian Banana Growers’ Council.</p

Model parameters.

a<p>Specified with reference to Cook <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042391#pone.0042391-Cook4" target="_blank">[30]</a> and Waage et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042391#pone.0042391-Waage1" target="_blank">[36]</a> using distributions defined in Biosecurity Australia <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042391#pone.0042391-Biosecurity1" target="_blank">[31]</a>; <i>^b</i> Derived from Sapoukhina et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042391#pone.0042391-Sapoukhina1" target="_blank">[37]</a>; <i>^c</i> ABS <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042391#pone.0042391-ABS1" target="_blank">[6]</a>, Note 1ha  = 10 000 m²; <i>^d</i> Ulubasoglu et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042391#pone.0042391-Ulubasoglu1" target="_blank">[38]</a>; <i>^e</i> Assumes average density of planting of 2 000 stems/ha and removal, transport, destruction and chemical costs amounting to $20/tree. This is inclusive of labour (team of three at$50/hr per person), bulldozing equipment ($100/hr at 20 hr/ha), truck hire ($75/hr), incendiaries ($60/ha for green waste) and creation of a circular chemical buffer zone approximately 5 ha in diameter around previously infected sites. Chemical used is assumed to be dithane (applied at a rate of 3 kg/ha or$25/ha) and oil (applied at 3L/ha or $10/ha) at fortnightly intervals rotated with propiconazole (applied at a rate of 0.3L/ha or$5/ha). Assume 2 additional dithane treatments are required and 4 propiconazole treatments (and therefore 6 additional oil treatments), each taking 1 hr/ha to apply; <i>^f</i> Assumes: (i) labour costs of $50/ha (i.e. 1 application × 1hr/ha ×$50/hr); (ii) 75 mL of chemical solution is used per banana plant per treatment costing $10/L (e.g. dimethoate diluted to 75 mL/100L) (i.e. approximately$15/ha); and (iii) two additional chemical treatments will provide sufficient suppression of banana aphid <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042391#pone.0042391-Cook4" target="_blank">[30]</a>.</p

Likely spread of BBTV over time with and without an active containment policy.

<p>Likely spread of BBTV over time with and without an active containment policy.</p

Policy and non-policy input parameters.

<p>Policy and non-policy input parameters.</p