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22: Host-plant Resistance

van Emden, H.F.; Harrington, R. CABI PDF

22

Host-plant Resistance

Helmut F. van Emden*

School of Agriculture, Policy and Development, The University of Reading,

Reading, UK

Introduction

In this chapter, the word ‘variety’ will be used as an umbrella word for the many types of variation involved; varieties, cultivars, accessions, breeders’ lines may all be included. The practical use of hostplant resistance (HPR) for aphid control in different crops is explored in the pest management section of this volume (Chapters 24–33).

It might be assumed that the role of symbionts in nitrogen metabolism (Chapter 6, this volume) should enable aphids to compensate for nutritional differences between crop varieties, and that the phloem-feeding habit would enable aphids to avoid many deterrent surface characters and allelochemicals in plants. However, the literature probably has more examples of HPR to aphids than to any other group of crop pests, including examples of nearly all the mechanisms of HPR known for insect pests in general. Moreover, HPR to aphids can be highly effective and dramatic; for example, the resistance of ‘Avoncrisp’ lettuce to Pemphigus bursarius (­lettuce root aphid) (Fig. 22.1).

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4: Life Cycles and Polyphenism

van Emden, H.F.; Harrington, R. CABI PDF

4

Life Cycles and Polyphenism1

Jim Hardie*

Royal Entomological Society, St Albans, UK, and Imperial College London,

Department of Life Sciences, Ascot, UK

Introduction

Aphids display a diverse range of relatively complicated life cycles associated with seasonal changes and the ephemeral availability of suitable hostplant material. The life cycle is divided into stages characterized by one or more specialist phenotypes/ morphs. Each of these morphs has a specific function that is necessary for the completion of that stage of the life cycle. Typical aphid life cycles have morphs that specialize in sexual and/or parthenogenetic reproduction, population dispersal/migration and surviving less favourable climatic or nutritional conditions. Not all morphs of pest species infest crop plants. How these life cycles, and related morphs, influence the likelihood of aphids becoming crop pests, when at least one host plant has economic significance, and the importance of the different life cycles for applied entomology are reported here.

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25: IPM Case Studies: Sorghum

van Emden, H.F.; Harrington, R. CABI PDF

25

IPM Case Studies: Sorghum

J.P. Michaud*

Department of Entomology, Kansas State University, Agricultural Research

Center – Hays, Hays, KS, USA

Introduction

Sorghum, Sorghum bicolor (Fig. 25.1), is a c­ ultivated grass species also known as great millet,

Guinea corn, Kafir corn and milo. Native to North

Africa, it is cultivated throughout tropical, subtropical and warm temperate regions. There are generally two types of sorghum, forage varieties and grain varieties. Both are grown mostly for animal feed and, more recently, for biofuel. In developing countries, grain varieties are grown for human consumption. Worldwide, 45.6 million ha of sorghum were harvested in 2014 (FAOSTAT,

2016).

There are four aphid species that commonly attack sorghum: Schizaphis graminum (greenbug),

Rhopalosiphum maidis (corn leaf aphid), Melanaphis sacchari (sugarcane aphid) and Sipha flava (yellow sugarcane aphid) (Fig. 25.2). Beginning in the late

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29: IPM Case Studies: Seed Potato

van Emden, H.F.; Harrington, R. CABI PDF

29

IPM Case Studies: Seed Potato1

Jon Pickup* and Christophe Lacomme

Science and Advice for Scottish Agriculture (SASA), Edinburgh, UK

Introduction

Potato Viruses and their Aphid Vectors

As potato is predominantly vegetatively (clonally) propagated; viruses that are systemic within the plant can be transmitted from one generation to the next through the planting of infected tubers.

The resulting virus-infected plants provide a source of inoculum during the growing season.

Approximately 40 viruses infect cultivated potatoes, of which 13 are primarily transmitted by aphids (Valkonen, 2007). The most widely distributed and common viruses, and therefore the most economically important viruses, are the aphidtransmitted polerovirus Potato leaf roll virus

(PLRV), the potyviruses Potato virus Y (PVY) and

Potato virus A (PVA) and the carlaviruses Potato virus M (PVM) and Potato virus S (PVS) (Gopal and Khurana, 2006). In Scotland, aphid-transmitted viruses are responsible for over 75% of the virus symptoms seen in classified seed potatoes.

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20: Biological Control

van Emden, H.F.; Harrington, R. CABI PDF

20

Biological Control1

Thierry Hance,1* Fatemeh Kohandani-Tafresh1 and Françoise Munaut2

1

Biodiversity, Earth and Life Institute, Université catholique de Louvain,

Louvain-la-Neuve, Belgium; 2Applied Microbiology, Earth and Life Institute,

Université catholique de Louvain, Louvain-la-Neuve, Belgium

Introduction

In recent decades, the development of new concepts in ecology, such as ecosystem services (Losey and

Vaughan, 2006), landscape ecology, food web complexity (Gagic et  al., 2011), apparent competition and mutualism, has changed our concepts of pest control. Consequently, the theoretical bases underlying the biological control of aphids have evolved towards a more integrated approach. The intensification of agriculture has led to an oversimplification of agricultural systems, and therefore also of the associated trophic systems. The extreme case is that of glasshouses, in which crops are increasingly grown hydroponically, without soil and fed with nutrient solutions. These simplified environments are particularly poor in natural enemies and are susceptible to pests.

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