Table Of ContentA TECHNICAL MANUAL FOR PARASITIC WEED RESEARCH AND EXTENSION
A Technical Manual for
Parasitic Weed Research and
Extension
Edited by
Jtirgen Kroschel
University of Kassel, Germany
Deutsche Gesellschaft fiir Technische Zusammenarbeit (GTZ)- University of Hohenheim
SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.
Library of Congress Cataloging-in-Publication Data
A technical manual for parasitic weed research and extension I edited by Jiirgen Kroschel.
p.cm.
1. Parasitic plants. 2. Weeds. 3. Parasitic plants--Control. 4. Weeds--Control. 5.
Parasitic plants--Research. 6. Weeds--Research. I. Kroschel, Jiirgen.
SB611 .T43 2001
632'.52--dc21
2001029163
ISBN 978-1-4020-0645-6 ISBN 978-94-010-0005-5 (eBook)
DOI 10.1007/978-94-010-0005-5
Printed on acid-free paper
All Rights Reserved
© 2001 Springer Science+Business Media Dordrecht
Originally published by Kluwer Academic Publishers in 2001
No part of the material protected by this copyright notice may be reproduced or
utilized in any form or by any means, electronic or mechanical,
including photocopying, recording or by any information storage and
retrieval system, without written permission from the copyright owner.
Dedicated to Prof. Dr. Werner Koch
Contents
Foreword ...................................................................................................................... xi
Acknowledgements ..................................................................................................... xiii
List of Contributors .................................................................................................... xv
1 Introduction ............................................................................................................. 1
1.1 Parasitic weed species and their hosts ................................................................ 1
1.2 Geographical distribution .................................................................................... 1
1.3 The life cycle of parasitic weeds ......................................................................... 3
1.4 Major books, symposium and workshop proceedings, field guides
and manuals ........................................................................................................ 5
2 Ecological studies .................................................................................................... 7
2.1 Preparation of herbarium samples ...................................................................... 7
2.2 Morphological studies ......................................................................................... 8
2.3 Population-genetic studies ................................................................................ 10
2.3 .1 Molecular markers ...................................................................................... 11
2.3.2 Use of DNA markers in the study of Orobanche and Striga ...................... 13
2.4 Ecological field assessments ............................................................................. 17
2.4.1 Determination of ecological behaviour ...................................................... 17
2.4.2 Toxic effects, transpiration, respiration and photosynthesis ...................... 19
3 Relevance to agriculture ....................................................................................... 23
3.1 Quantification of infestation and yield loss ...................................................... 23
3 .1.1 Field survey ................................................................................................ 23
3 .1.2 Yield loss assessment ................................................................................. 25
3.2 Analysis of farming systems ............................................................................. 29
4 Seed features, germination and seed bank. ......................................................... 31
4.1 Reproductive capacity ....................................................................................... 31
4.2 Seed collection .................................................................................................. 33
4.3 Testing seed viability ........................................................................................ 35
4.4 Assessment of germination ............................................................................... 36
4.4.1 Conventional germination test.. .................................................................. 36
4.4.2 Agar gel test ................................................................................................ 40
vii
4.5 Extraction from soil .......................................................................................... 42
4.5.1 Soil sampling .............................................................................................. 43
4.5.2 Methods to separate seeds from soil.. ......................................................... 45
4.6 Detection from crop seed .................................................................................. 50
4.7 Seed bags in soil ............................................................................................... 51
5 Investigations on developmental stages .............................................................. 53
5 .1 Laboratory experiments .................................................................................... 53
5.1.1 Observations ofthe underground development.. ........................................ 53
5. 1.2 In vitro culture ............................................................................................ 59
5.1.2.1 In vitro culture of Striga hermonthica .................................................... 59
5.1.2.2 In vitro culture ofOrobanche aegyptiaca .............................................. 61
5.2 Pot experiments ................................................................................................ 63
5.3 Field experiments ............................................................................................. 66
5.3.1 Site selection and preparation ..................................................................... 66
5.3 .2 Artificial infestation .................................................................................... 68
5.3.3 Developing parasite free areas .................................................................... 72
5.3 .4 Experimental design for field experiments ................................................. 72
5.3.5 Data collection in field experiments ........................................................... 74
6 Application of control methods ........................................................................... 77
6.1 Preventive ......................................................................................................... 77
6.1.1 Prevention after harvest.. ............................................................................ 79
6.2 Cultural ............................................................................................................. 81
6.2.1 Crop rotation with non-hosts, trap and catch crops .................................... 81
6.2.2 Sowing date ................................................................................................ 83
6.2.3 Mineral fertiliser and organic material ....................................................... 85
6.2.4 Duration of fallow period and managed fallow .......................................... 88
6.2.5 Flooding ...................................................................................................... 89
6.3 Host plant resistance and tolerance .................................................................. 91
6.3 .1 Breeding for resistance to Oro bane he ........................................................ 92
6.3 .1.1 Screening techniques and sources of resistance ..................................... 92
6.3 .1.2 Genetics of resistance ............................................................................. 98
6.3 .1.3 Breeding strategies ................................................................................. 99
6.3.2 Breeding of cereals for resistance to Striga .............................................. 100
6.3 .2.1 Screening techniques and selection traits ............................................. 100
6.3.2.2 Variability within and among Striga species, and stability
of resistance ........................................................................................... 104
6.3.2.3 Sources of resistance ............................................................................ 105
6.3.2.4 Genetics of resistance ........................................................................... 106
6.3.2.5 Breeding strategies ............................................................................... 107
6.3 .3 Breeding for resistance to Alectra vogelii and Striga gesnerioides ......... 108
6.3.4 Resistance to Cuscuta ............................................................................... 109
viii
6.3.5 Use of molecular markers ......................................................................... 110
6.3.6 Genetic engineering .................................................................................. 112
6.4 Chemical ......................................................................................................... 114
6.4.1 Soil disinfection ........................................................................................ 114
6.4.2 Herbicides ................................................................................................. 116
6.4.3 Germination stimulants ............................................................................. 120
6.4.3.1 Ethylene gas .......................................................................................... 120
6.4.3.2 Strigol and analogues ............................................................................ 121
6.5 Physical ........................................................................................................... 123
6.5.1 Cleaning of crop seed ............................................................................... 123
6.5.2 Hand weeding ........................................................................................... 124
6.5.3 Burning ..................................................................................................... 126
6.5.4 Deep ploughing ......................................................................................... 127
6.5.5 Solarization ............................................................................................... 128
6.6 Biological ........................................................................................................ 131
6.6.1 Phytophages .............................................................................................. 131
6.6.1.1 Collection of insect species .................................................................. 133
6.6.1.2 Field observation of insects .................................................................. 135
6.6.1.3 Rearing of insects ................................................................................. 139
6.6.1.4 Biological control of Oro bane he .......................................................... 141
6.6.2 Pathogens .................................................................................................. 144
6.6.2.1 Survey ................................................................................................... 144
6.6.2.2 Isolation ................................................................................................ 145
6.6.2.3 Classification ........................................................................................ 146
6.6.2.4 Storage .................................................................................................. 14 7
6.6.2.5 Inoculum production ............................................................................. 148
6.6.2.6 Screening .............................................................................................. 149
6.7 Toxins ............................................................................................................. 151
6.7.1 Biological assays to test toxins ................................................................. 151
6.8 Integrated ........................................................................................................ 155
7 Putting it into practise ........................................................................................ 159
7.1 Training of researchers, extension staff and farmers ...................................... 159
7 .1.1 International training courses ................................................................... 161
7 .1.2 National training of extension staff .......................................................... 163
7.1.3 Trainingoffarmers ................................................................................... 167
7.2 Extension aids ................................................................................................. 169
7 .2.1 Picture series ............................................................................................. 169
7 .2.2 Printed material. ........................................................................................ 179
7.3 On-farm experimentation ................................................................................ 182
8 Glossary ................................................................................................................ 189
ix
9 List of crop scientific names ............................................................................... 203
10 Literature .......................................................................................................... 205
11 Annex ................................................................................................................ 227
11.1 Key to the main Striga spp. (according to Parker & Riches 1993) ................ 227
11.2 Key to the main Alectra spp. (according to Parker & Riches 1993) .............. 228
11.3 Key to the main Oro bane he spp. (according to Parker & Riches 1993) ........ 228
11.4 Key to the main Cuscuta spp. (according to Parker & Riches 1993) ............. 229
11.5 The life-cycles of Striga, Orobanche and Cuscuta ........................................ 233
11.6 List of trap crops for Orobanche spp. and Striga spp .................................... 235
11.7 Form for a site description .............................................................................. 23 7
11.8 Data sheet for the quantification of Striga infestation and yield
loss assessments .............................................................................................. 23 9
11.9 Example of a questionnaire for the analysis of farming systems ................... 240
11.10 Programme of a three days training workshop ............................................ 246
11.11 Example for a benchmark test ..................................................................... 248
11.12 Example for a questionnaire used for the evaluation of a training course .. 251
11.13 Striga, an enemy to all farmers - a radio play ............................................. 253
12 Color Plates ....................................................................................................... 257
X
Foreword
Parasitic weeds are known to be diffi cuta. It summarises procedures, which
cult to control in agricultural produc have been practically applied or devel
tion. Despite an enormous increase in oped either by researchers of the supra
knowledge of their biology and the de regional project "Ecology and Man
velopment of different control options, agement of Parasitic Weeds" of the
no substantial reduction of infestation Deutsche Gesellschaft fur Technische
has been achieved in the past either Zusammenarbeit (GTZ) GmbH, which
with regard to Orobanche spp. in the was carried out in co-operation with the
Mediterranean region or with regard to University of Hohenheim from 1988 to
Striga spp. in sub-Saharan Africa. 1998, or by researchers from Interna
tional Agricultural Research Centres
The specific biology of parasitic weeds
and Advanced Research Institutes.
is still a great obstacle for the develop
ment of control strategies. Most of the It is not claimed to list all possible
host plant damage is already done be techniques applied so far in studies on
fore the parasites' emergence above parasitic weeds, nor can the respective
ground. This means that control tools descriptions of each procedure cover
are needed which interfere with the un each and all aspects in full detail. It is
derground stages in order to protect the merely intended to offer a palette of
present crop. Until now, we have only possibilities and to give hints on practi
few control methods available which cal aspects related to the specific re
fulfil these requirements. In addition, quirements of a parasite or a technique.
research has to deal with various para When required, further in depth infor
sites, which attack a wide range of mation on any given subject might be
crops in different agro-ecosystems. This drawn from the specific reports in the
implies that solutions specific to para literature of which a selection is pro
sites, crops and farming systems must vided at the end of each chapter.
be developed. In many countries and
One intention regarding the compilation
regions it has been shown that the
of methods into this manual was to pro
knowledge of extension workers related
vide easy handling of the techniques.
to the biology and control of parasitic
Hence, wherever possible and appropri
weeds has to be improved as a prereq
ate, throughout the manual the follow
uisite to assist farmers adequately in
ing structure was applied:
their control efforts. In addition, suit
INTRODUCTION: background, over
able extension methods and strategies
view, principle of the method.
have to be developed with and for ex
OBJECTIVE(S): aim(s) ofthe method.
tension services in order to support ex
MA TERIAL(S): list of items including
tension workers in the transfer of possi
chemicals, equipment, time re
ble solutions.
quirement.
This "Technical Manual for Parasitic
PROCEDURE(S): implementation, pre
Weed Research and Extension" pro paration, sample size.
vides methodologies for various aspects
EVALUATION: hints for data collec
of research and extension related to
tion, calculations, evaluation and
parasitic weed species of the genera
statistical aspects.
Striga, Alectra, Orobanche and Cus-
Xl
