6 Plant Health
The economic consequences of crop pests and diseases include:
- the value of crops lost or damaged as a result of outbreaks of pests and diseases; and
- the cost incurred by farmers to try to prevent and control pests and disease.
Around the world plant pests and diseases are estimated to be responsible for losses ranging from between 20% to 40% of global production  . Protecting crops from disease therefore has the potential not only to make a very significant contribution to global food security but also to the value of agricultural output.
This chapter considers the contribution that scientists funded by the 2011-16 SRP have made (and continue to make) to limiting the damage of plant pests and diseases in Scotland.
6.1 Contribution of the 2011-16 SRP
According to statistics produced by the Scottish Government the total value of crops produced in Scotland in 2015 amounted to £820.7 million.  Two crops accounted for around 45% of this output: barley (£198.1 million) and potatoes (£167 million). Although scientists funded by the 2011-16 SRP are engaged in research on a variety of pests and diseases research on pests and diseases that affect these two crops was a particularly important focus.
In recent years one of the most important diseases effecting barley in the UK (and elsewhere) has been Ramularia. Scientists in the 2011-16 SRP have been at the forefront of tackling this disease. The case study below describes this work and quantifies the contribution it has made to Scottish agricultural output.
Case Study 6‑1 - Tackling Ramularia
In the late 1990s barley growers in Scotland began noticing symptoms of an unrecognised disease that reduced yield and resulted in thinner grains. Plant pathologists based in one of the MRPs identified that these symptoms were being caused by a pathogen that had not previously been recorded in Scotland and applied for funding from the Scottish Government to help tackle the emerging threat.
The first phase of the research was to identify the disease and the best control measures (fungicides) for controlling it. The next stage was to develop a diagnostic test to enable growers to identify the disease before symptoms emerge.
After the initial research was completed the fungus that causes Ramularia developed resistance to the fungicide that had been identified to control it, forcing scientists to identify an alternative. In the years since the original research was undertaken the fungus has continued to evolve, which has created an on-going need to monitor fungicide sensitivity so that alternative measures can be identified and adopted as necessary. This on-going monitoring has been a key focus of research funded by the 2011-16 SRP and has enabled scientists at the MRP to develop best practice guidance on the control of Ramularia that has been widely adopted across the UK.
In the absence of proper control measures it has been estimated that losses due to Ramularia would (on average) equate to 0.5 tonnes/hectare. Implementing the best practice control strategies developed by the MRP reduces these losses (on average) to a maximum of 0.2 tonnes/hectare. Based on the current average yield of 6.6 tonnes/hectare, this represents an improvement in yield of around 4.5% on unprotected crops.
This implies that crop yields have improved by around 0.3 tonnes/hectare as a direct result of work undertaken by the MRP. By applying this estimate to the actual amount and value of barley produced in the UK in 2015 it was estimated that the value of this output was £37.5 million GVA. Using the same method it was estimated that Scottish growers could accrue around £9.0 million GVA of this value.
Ramularia first emerged in central Europe but it has now spread to all major barley growing regions around the world. The expertise developed as a result of this research means that the advice of scientists at the MRP is now much sought after by barley growers all over the world. With authorities in Europe estimating that Ramularia could reduce yield by up to 20% and authorities in South America estimating losses of up to 70% this means that the global implications of this work could be very substantial indeed.
Source: BiGGAR Economics based on Consultation with MRP staff
Accounting for 20% of the total value of Scottish crop production potatoes are Scotland's second most valuable crop. The two most important pathogens affecting potatoes in the Scotland are late blight and potato cyct nematodes ( PCN). It has been estimated that these pathogens together cost the UK economy a total of £81 million/year  . Scotland currently accounts for around 30% of the value of the UK potato crop so this implies that these diseases are likely to cost the Scottish economy in the region of £25 million/year.
Scientists funded through the 2011-16 SRP have been particularly active in addressing these pathogens and helping to contain their cost to the Scottish economy. The funding has for example been used to develop an empirical model that can be used to project the risk of PCN in 36,000 crop locations around the UK. An understanding of such risks is of fundamental importance to the decisions farmers make about when and how much fungicides to apply to their crops, which can significantly reduce the cost of crop damage and losses. Funding from the 2011-16 SRP has also been used to sequence the genome of one of the most damaging species of PCN, which is expected to be key to future control efforts.
Direct evidence about the economic benefits of this research is not readily available but can be estimated based on recent experience in barley production.
As discussed in the case study above, research funded by the 2011-16 SRP has resulted in an increase of around 4.5% in the yield of barley across the UK. It is not unreasonable to expect that the research undertaken on important potato pathogens would have resulted in a similar level of improvement within the potato crop. By applying this to the volume and value of potato production in Scotland in 2015 it was possible to estimate that the value of agricultural production was around £7.6 million higher than it otherwise would have been as a result of this research. Using the same approach it was estimated that the benefit to the UK economy as a whole amounted to £24.9 million in 2015.
6.2 The Counterfactual
The benefits described in this chapter can be considered additional to the Scottish economy for the same reasons described in section 5.3: public funding is necessary to overcome the risks associated with uncertain returns to early stage research. Without this funding there would be a market failure and the private sector would not undertake this type of research.
6.3 Summary Benefits
By adding together the two sources of benefit considered in this chapter it was estimated that research funded by the 2011-16 SRP reduced the cost of important crop pests and diseases to the Scottish economy by £16.6 million GVA in 2015. Across the UK as a whole the value of this benefit was estimated at around £62.3 million GVA. These impacts are summarised in the table below.
Table 6‑1: Annual impact of plant health improvements - GVA (£ millions)
|PCN & Late Blight||7.6||24.9|
Source: BiGGAR Economics
6.3.1 Impact Time-Scale
The impacts described in this chapter are underpinned by many years of research evidence but the nature of plant pests and diseases means that it is appropriate to include these impacts as part of this analysis. This is because, although expertise and understanding of particular pathogens may be based on historic research, the methods used to predict and control them are constantly evolving.
Like the plants they affect, plant pests and diseases evolve continually. As soon as a new control method is implanted the pathogen involved starts changing in order to circumvent it. The challenges presented by these pathogens have also been compounded in recent years by the withdrawal of some of the most effective chemical control treatments on environmental grounds.
This means that tackling pests and diseases is an on-going battle where standing still is not an option and the benefits of previous advances are quickly eroded, as in the case of the study above where the fungus that causes Ramularia developed resistance to the fungicides used to control it.
Research supported by the 2011-16 SRP has enabled scientists to continue to develop new and improved control strategies, thereby helping to avoid the benefits of previous scientific advances being eroded. It is therefore appropriate to attribute the value of these benefits to the 2011-16 SRP.
Email: Eilidh Totten, Eilidh.Totten@gov.scot
Phone: 0300 244 4000 – Central Enquiry Unit
The Scottish Government
St Andrew's House