Abstract Ramaiah, K.V., Parker, C., V a s u d e v a R a o . M.J., a n d M u s s e l m a n , L.J. 1983. Striga identification a n d control handbook. Information Bulletin No. 15. P a t a n c h e r u , A.P., India: International Crops Research Institute for the Semi-Arid T r o p i c s . Striga is a root parasite of m a n y f o o d c r o p s . It c a u s e s serious yield losses throughout the s e m i - a r i d tropics. T h e purpose of this bulletin is to c r e a t e i n c r e a s e d awareness of the need to reduce such losses associated with Striga infestations. It d e s c r i b e s t h e most important of the 25 s p e c i e s of t h e w e e d o c c u r r i n g in the world, their biology, and s y m p t o m s of attack. It also provides brief information a b o u t the options for controlling the parasite. A key is presented to assist in the identification of the seven m o s t d a m a g i n g s p e c i e s of Striga, and the text is s u p p o r t e d by 34 illustrations in color. The International Crops Research Institute lor the Semi-Arid Tropics (ICRISAT) is a nonprofit scientific educational institute receiving support from donors through the Consultative Group on International Agricultural Research. Donors to ICRISAT include governments and agencies of Australia, Belgium, Canada, Federal Republic of Germany, France. India, Italy, Japan, Mexico, the Netherlands, New Zealand, Nigeria, Norway, Sweden, Switzerland, United Kingdom, United Slates, and the following international and private organizations: Asian Development Bank, Euro- pean Economic Community, Ford Foundation, International Bank for Reconstruc- tion and Development, International Development Research Centre, International Fertilizer Development Center, Internalional Fund for Agricultural Development, Leverhulme Trust, Organization of Petroleum Exporting Countries, Rockefeller Foundation, and the United Nations Development Programme. Responsibility for the information in this publication rests with ICRISAT. Where trade names are used this does not constitute endorsement of or discrimination against any product by the Institute. Correct citation: RAMAIAH, K.V., PARKER, C, VASUDEVA RAO, M.J., and MUSSELMAN, L.J. 1983. Striga identification and control handbook. Information Bulletin No. 15. Patancheru, A.P., India: International Crops Research Institute for the Semi-Arid Tropics. STRIGA IDENTIFICATION AND CONTROL HANDBOOK K.V. R a m a i a h ICRISAT, B.P. 1165, Ouagadougou, Upper Volta W e s t A f r i c a C . P a r k e r Weed Research Organization, Begbroke Hill, Y a m t o n , O x f o r d , O X 5 1PF, U K M . J . V a s u d e v a R a o ICRISAT Center, Patancheru P.O. A n d h r a P r a d e s h 5 0 2 3 2 4 , India L.J. M u s s e l m a n O l d D o m i n i o n University, Norfolk, Virginia 2 3 5 0 8 , USA Published by the International Crops Research Institute tor the Semi-Arid Tropics with financial assistance from the Inter- national Development Research Centre (IDRC), Canada. ICRISAT Information Bulletin No. 15 International Crops Research Institute for the Semi-Arid Tropics ICRISAT Patancheru P.O. Andhra Pradesh 502324, India 1983 Contents INTRODUCTION 3 BIOLOGY 4 S e e d s 4 Germination 4 Haustorial initiation 8 A t t a c h m e n t 8 N u t r i t i o n 8 L i f e c y c l e 1 3 STRIGA S P E C I E S 1 4 Striga asiatica 14 Striga hermonthica 2 0 Striga densiflora 2 3 K e y t o m a i n Striga s p e c i e s 2 6 - 2 7 Striga euphrasioides 2 9 Striga aspera 3 2 Striga gesnerioides 3 2 Striga forbesii 3 6 S Y M P T O M S O F STRIGA A T T A C K 3 6 C O N T R O L M E A S U R E S 3 9 R e s i s t a n t c u l t i v a r s 4 4 Striga-pulling by h a n d 4 4 R o t a t i o n s 4 6 N i t r o g e n fertilizer 4 6 H e r b i c i d e s 4 6 Germination stimulants 4 7 B i o c o n t r o l 4 7 I n t e g r a t e d c o n t r o l 4 7 P h o t o C r e d i t s 5 1 INTRODUCTION P l a n t s of Striga genus (Scrophulariaceae) are generally k n o w n a s w i t c h w e e d s . T h e g e n u s i n c l u d e s a b o u t 2 5 s p e c i e s , o n l y a f e w o f w h i c h a r e e c o n o m i c a l l y i m p o r - tant, for i n s t a n c e S. hermonthica, S. asiatica, S. gesne- rioides, S. densiflora, S. euphrasioides, S. aspera, a n d S. forbesii (in o r d e r of i m p o r t a n c e ) . S p e c i e s r a n g e f r o m a l m o s t c o m p l e t e l y p a r a s i t i c t o a l m o s t totally a u t o t r o - p h i c . T h e y a t t a c k s e v e r a l f o o d c r o p s , m a i n l y c e r e a l s , but a l s o s o m e b r o a d - l e a v e d c r o p s s u c h a s c o w p e a . T h e r e i s a w i d e r a n g e o f wild h o s t s . T h o u g h p r e c i s e c r o p l o s s e s t i m a t e s a r e difficult t o m a k e , c o m p l e t e c r o p fail- u r e s c a u s e d b y Striga h a v e b e e n r e c o r d e d , a n d o c c u r i n m a n y r e g i o n s of A f r i c a a n d India. C o n t r o l of Striga c o u l d not o n l y i n c r e a s e f o o d p r o d u c t i o n in Striga-infested l a n d , b u t a l s o b r i n g b a c k into c u l t i v a t i o n l a n d that w a s p r e s e n t l y a b a n d o n e d b e c a u s e of Striga infestation. Unfortunately, Striga is still c o n s i d e r e d as a w e e d n u i s a n c e a n d n o t a s t h e i m p o r t a n t a g r i c u l t u r a l pest i t is. T h o u g h f a r m e r s w h o s e p l a n t s suffer Striga a t t a c k r e c - o g n i z e it as a p r i m a r y y i e l d - r e d u c e r of t h e i r f o o d c r o p s , t h e e x t e n t o f t h e p r o b l e m h a s s o far not b e e n r e a l i z e d b y r e s e a r c h a n d e x t e n s i o n a g e n c i e s a n d t h e i r d o n o r s .