AHDB Potatoes 1240001 FINAL Report
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Final Edition PCN Management - Reference Guide 28 Jan 16 AHDB Potatoes Research Project: Provision of Content for a PCN Management Guide (No: 1240001) 1 May 2015 - 31 January 2016 Potato Cyst Nematodes (PCN) - Their Characteristics and Guide to Management Produced by: Sue Hockland, Matt Back, Vivian Blok, Kim Davie, Ivan Grove, John Jones and Jon Pickup Co-ordinator/Editor: Sue Hockland Table of Contents Chapters and Sections Page No. List of Contents 1 Chapter 1 Introduction 4 Chapter 2 History: Origin and Spread 6 Chapter 3 Biology and Distribution of PCN species, including 7 Life Cycle, Population Dynamics and factors influ- encing them 3.1 Species and Distribution 7 3.2 Life Cycle 10 3.2.1 Introduction 10 3.2.2 Hatching 11 3.2.3 How juveniles become established in a host 14 3.2.4 Maturity, death, and the next generation 16 3.2.5 Rate of Decline 16 3.2.6 Multiplication rates 19 3.2.7 Influence of Temperature 20 3.2.8 Influence of soils 22 1! Final Edition PCN Management - Reference Guide 28 Jan 16 3.2.9 Host plants 22 3.2.10 Local spread 22 3.2.11 The increasing impact of molecular research on 22 knowledge of PCN biology 3.2.12 Virulence and pathotypes 24 Chapter 4 Characteristics of Potato Varieties 27 4.1 The development of resistant varieties by plant 27 breeders 4.2 Pathogenecity, Virulence, Resistance and Toler- 31 ance: understanding their effects for PCN Man- agement 4.2.1 Definitions and Introduction 31 4.3 Categorisation of resistance levels 33 4.4 Effects of using resistant varieties in the UK and 35 Europe Chapter 5 Yield loss; evidence for effect on yield 41 Chapter 6 Steps to determine appropriate control measures 44 6.1 Introduction 44 6.2 Sampling and detection 45 6.3 Viability 50 6.4 Thresholds 51 6.5 Revised Thresholds for action in PCN Manage- 53 ment Chapter 7 Management Options 55 7.1 Introduction 55 7.2 Using knowledge of the biology and life cycle of 57 PCN 7.2.1 Extend length of rotation 57 7.2.2 Minimising spread 59 7.2.2.1 Use certified seed potatoes 59 7.2.2.2 Hygiene 59 7.2.2.3 Disposal of soil residues at harvest 61 7.2.3 Control of volunteer potatoes 61 7.3 Use potato varieties resistant to PCN 61 7.4 Trap cropping 64 2! Final Edition PCN Management - Reference Guide 28 Jan 16 7.5 Biofumigation 66 7.5.1 Introduction 66 7.5.2 The biofumigation process 67 7.5.3 Factors affecting biofumigation 69 7.5.4 Summary of work investigating biofumigation for 71 PCN management 7.6 Chemical Control 74 7.7 Biological Control 84 7.7.1 Pochonia chlamydospora and other fungal para- 85 sites 7.7.2 Bacterial parasites 87 7.7.3 Manipulating PCN/plant interactions 88 7.7.4 Control using miscellaneous plant extracts, agricul- 88 tural residues and other soil amendments 7.7.5 Inundation (flooding) and other anaerobic soil dis- 90 infestations Chapter 8 Decision Pathways 91 Chapter 9 Concurrent Projects and Future Research Needs 92 Acknowledgements 93 Glossary 94 Disclaimer 96 References 97 List of Figures 127 List of Tables 128 3! Final Edition PCN Management - Reference Guide 28 Jan 16 Chapter 1. Introduction The spread of Globodera pallida, and the withdrawal of many pesticide controls, has necessitated a major reassessment of criteria for control of both species of PCN. Since the MAFF guide to PCN Management was issued in 1999, there have been several advances in knowledge of PCN development, the development of potato varieties resistant to G. pallida as well as G. rostochien- sis, and other new tools to assist in reducing population levels before the next crop. The biology and management of PCN is a complex subject, and it is clearly apparent that the characteristics of PCN differ not only according to species, but also according to local environmental conditions; thus this Reference Guide will present current knowledge, but local observations are invaluable for making the right decisions. The aim of this Reference Guide is to put science into practice and provide guidelines for the management of potato cyst nematodes (PCN) and so improve production levels in the UK. Commercial demands may have to be reviewed if the long-term control of PCN and the future of the industry is to be sustained, especially when evidence is accumulating that viable eggs can remain in cysts for 40 years or more. An earlier guide for the management of PCN produced by MAFF in 1999 (Lane & Trudgill, 1999) was in response to a need to manage the emergence of G. pallida, as it is more troublesome to control than G. rostochiensis. The former is now the predominant species, and a reduction in the range of nematicides/nematistats to control it has demanded a more sustainable approach if the area of potato growing land is to be protected. For decades, PCN have remained a major pest of potatoes in the UK, and there are new records world- wide each year. In 2010, the EU published a new PCN Control Directive (EU Council Di- rective 2007/33/EC - Anon, 2007), to spearhead a more collaborative approach to the management of this pest in Europe (Hockland, 2010). The development of molecular sci- ence has increased our understanding of PCN, but several problems, such as the increas- ing importance of G. pallida, and availability of commercially-viable resistant varieties, re- main. There are several recommended management tools integrated into this Reference Guide. Potato varieties showing resistance to the PCN species are key components. However, to date, the commercial popularity of certain varieties for the fresh sector or processing has 4! Final Edition PCN Management - Reference Guide 28 Jan 16 assumed a greater importance than using a PCN resistant variety and this has been large- ly responsible for an increase in PCN populations. This situation must receive greater at- tention from potato processors and retail outlets, whose involvement in PCN management is critical. The identification of species is an essential precursor to choice of variety. Any control pro- gramme should allow a tailored approach to every field, yet it seems that many manage- ment strategies are based on assumptions of the species present. Knowledge of the life cycle of the particular PCN species present would facilitate plans regarding the choice of variety, length of rotation, a realistic assessment of the likely effectiveness of chemical products, and risk of more than one generation occurring. Whilst sampling and detection methods are essential to provide the raw data for determin- ing the optimal path for management, procedures vary nationally, and are notorious for be- ing subject to variation and error. This Reference Guide advocates an approach that uses the detection of any viable cyst as the trigger for action. However, there is no ‘silver bullet’. Sampling techniques should be carefully considered to maximise the chances of detection in a field, bearing in mind cropping history and likely pathways for spread; levels of infesta- tion should be monitored and the results used in decision-making for management meth- ods in a particular field. The decrease in the availability of chemical tools has increased attention into research for biological control, but to date these remain to be developed for commercial use. The most important contribution a grower or buyer can make to sustainable PCN management in in- fested fields is to use a potato variety of the required resistance grading; this Reference Guide emphasises that importance. However, there is also potential for trap crops and bio- fumigants to become an integral part of control measures. Above all, it is clear that the management of PCN is a complex subject, and requires de- tailed knowledge of the characteristics of the local PCN population and environmental conditions to develop a successful strategy for any particular field. 5! Final Edition PCN Management - Reference Guide 28 Jan 16 Chapter 2. History: Origin and Spread Knowledge of the origin and pathways of spread of both PCN species can contribute to an understanding of those factors that will facilitate its management. The PCN species considered in this Reference Guide are closely related species, namely Globodera pallida (Stone, 1973) and G. rostochiensis (Wollenweber, 1923) Skarbilovich, 1959, which co-evolved with the wild potato in South America several hundred thousand years ago (Stone, 1979). Molecular studies are providing increasing evidence that the an- cestors of populations in Europe probably came from a few introductions, probably from southern Peru in the 19th century. Several expeditions were made then to central and south America in order to procure new, cultivated potato varieties resistant to potato blight (Phytophthora infestans) (Turner & Evans, 1998). However, some of the introductions into Europe may have been via routes other than as contaminants of potato tubers. Inagaki & Kegasawa (1973) found viable cysts of G. ros- tochiensis in Peruvian guano, imported into Japan from deposits located off the coast of Peru. It seems most likely that the guano was shipped in PCN-contaminated potato sacks, and may have been introduced to Europe this way from the 1840s onwards, explaining the presence of the two species here today. Historical records suggest that G. rostochiensis may have arrived in the USA in soil on military or agricultural equipment (Hockland et al. 2013), thus illustrating the need to be vigilant on all potential pathways. A recent report from the European Food Safety Authority (EFSA) Panel on Plant Health delivered a scientific opinion on different risks posed by European and non-European pop- ulations of PCN to potatoes and other solanaceous plants in the EU and on the effective- ness of current control measures (EFSA Panel on Plant Health (PLH) (2012)).