It is widely accepted that potato cyst nematodes are a serious threat to the viability of potato production and yet despite efforts to promote better management practices the area of infested land continues to increase in the UK. There are many explanations for this trend, not least the lack of market acceptance to those varieties with good resistance, which is considered essential to reducing populations, but the dwindling supply of clean land is also a serious concern, according to an article by Bayer Crop Science in the UK.
Bayer says in the article that the situation is especially acute in Scotland where the need for PCN-free land is vital to maintaining the country’s status as a leading producer of clean seed. A Scottish Government report produced by the Plant Health Centre at The James Hutton Institute considered the situation and what was needed to improve it for the long-term.
The report, The future threat of PCN in Scotland, found that the area of land infested with Globodera pallida is doubling every seven to eight years. Should this rate of increase continue, say the authors, “the widespread presence of G. pallida may prohibit the production of seed potatoes on PCN-free land in as little as 30 years”. The authors note that this level of infestation will also limit the production of ware potatoes through loss of yield.
The financial impact of this is significant. On average, PCN is reckoned to incur an opportunity cost to growers of roughly £5,093 per hectare in lost output which equates to a £25m loss for growers in Scotland in 2019. The authors used this per hectare estimate to calculate the income forgone in the year 2040 should the area of infested land continue to increase at the current trajectory. It estimated this loss to be £125m.
With the threat to the long-term production of potatoes in Scotland so apparent, the authors spoke to growers in a bid to understand why the problem was getting worse, not better. Specifically, they sought to identify why growers were not planting resistant varieties or making better use of the other means of control and what could be done to make PCN management more effective.
The findings identify external barriers such as a lack of choice over the variety to be grown which serves to hamper the adoption of resistant varieties and the absence of a climate in Scotland conducive to achieving the dry matter content required of processing varieties, which tend to be the varieties with good resistance to G. pallida.
The unsuitability of some biofumigant and catch crops to Scottish conditions is also identified. “Despite their potential, trap crops are not widely practicable for use in Scotland as they do not establish well in the climate,” notes the report.
The authors note that resistant varieties and long rotations are probably the most effective means of protecting PCN-free status, but “unless groundkeepers are controlled, long rotations are broadly meaningless”.
In the Netherlands, where PCN infestations are higher than in the UK, “crops are monitored, and restrictions placed on land where too many ground keepers are recorded.” If the tolerance is exceeded the land is treated as if a potato crop has been planted.
The report notes that PCN is not the dominant issue when considering which variety to grow. Most of the growers surveyed view blackleg as the main concern as this is responsible for most down-gradings. PCN came third on the list of concerns with late blight control second.
Perhaps most concerningly, the report identified a lack of knowledge and understanding about PCN or the threat it posed to the long-term production of the crop.
The authors noted the following:
- The need for greater information sharing. “From interviews with growers it became clear that knowledge about PCN, how it multiplies, how it is spread and how to control it is limited. This is particularly true for ware growers who see little economic impact of PCN, as well as for landowners who rent out land to potato growers.”
- Guidance on how to interpret soil sampling results. “Results of PCN testing does not influence the choice of varieties planted on infested land. Lack of appropriate knowledge/advice on the best course of action and, secondly, a lack of choice when it comes to selecting resistant varieties are the main limiting factors.
“Where a PCN test returns a ‘none found’ result, there is a belief that the land is PCN-free and therefore there is no need to manage the land for PCN. This appears to be an important knowledge gap for growers and where increased education is required.
Source: Bayer Crop Science (UK). Read the full article on the Bayer Crop Science website here.