Biology, ecology and management of the sweetpotato weevil, Cylas puncticollis Boheman (Coleoptera: Brentidae) By Amin EL Zubeir Gubartalla Mohamed B. Sc. (Agric.) Hons., M. Sc. (Agric.) University of Khartoum A thesis submitted in fulfillment of the requirements for the degree of Doctor of Philosophy Supervisor: Prof. EL-Imam EL-Khidir Co-supervisor: Dr. Kamal Mowafi Crop Protection Department Faculty of Agriculture University of Khartoum March 2005 1 DEDICATION To the memory of my beloved late mother Rabaa 2 CONTENTS Pag e Dedication i Contents ii A knowledgements vi Abstract viii Arabic Abstract x 1. INTRODUCTION…………………………………… 1 ……. 2. REVIW OF 5 LITERATURE………………………………… 2.1 5 Taxonomy and distribution……………………………………. 2.2 7 Host range…………………………………………………. …. 2.3 8 Economic impact and damage……………………………….... 2.4 10 Biology………………………………………………… ……… 2.4.1 Description…………………………………………… 10 ………. 2.4.2 Life 11 history………………………………………………… 3 … 2.4.3 Effect of temperature on the development of the sweetpotato 14 weevil………………………………………………… ………. 2.5 Effect of sweetpotato root characters on the infestation of sweetpotato 15 weevil……………………………………………. 2.6 18 Influence of irrigation on sweetpotato weevil infestation…….. 2.7 Control………………………………………………… 21 ……… 2.7.1 21 Cultural control……………………………………………….. 2.7.1. 22 Crop 1 rotation………………………………………………… .. 2.7.1.2 Intercropping ………………………………………………… 23 2.7.1.3 Earthing up the soil (hilling)…………………………………. 23 2.7.1. 2 Sanitation and destruction of crop 4 4 residues…………………… 2.7.1. 2 Clean 5 5 4 cuttings…………………………………………………. 2.7.2 2 Host-plant 6 resistance…………………………………………. 2.7.3 3 Biological 0 control…………………………………………….. 2.7.4 3 Chemical 1 control……………………………………………… 2.7.5 Integrated pest management (IPM)…………………………… 3 5 3. 3 MATERIALS AND METHODS……………………………. 8 3.1 Survey………………………………………………………… 3 … 8 3.2 Laboratory experiments (first season 3 2001/02)…………………. 8 3.2.1 3 Life history of sweetpotato 9 weevil……………………………… 3.2.1. 3 Duration of development of immature 1 9 stages…………………... 3.3 Field experiments (first season 4 2001/02)……………………….. 0 3.3.1 The influence of irrigation intervals and sweetpotato clones on sweetpotato weevil infestation (autumn transplanting 4 experiment) 1 5 3.3.2 The influence of irrigation intervals and sweetpotato clones on sweetpotato weevil infestation (winter transplanting 4 experiment) 4 3.3.3 Sweetpotato weevil 4 management…………………………….…... 4 3.4 Laboratory experiments (second season 4 2002/03)……………….. 6 3.4.1 4 Life history of sweetpotato weevil, Cylas puncticollis 6 Boh……… 3.4.1. Duration of development of immature 4 1 stage……………………... 6 3.4.1. Preoviposition 4 2 period…………………………………………….. 6 3.4.1. Oviposition 4 3 rate…………………………………………………... 6 3.4.1. Sex 4 4 ratio…………………………………………………………... 7 3.5 Field experiments (second season 2002/03)…………………….. 47 3.5.1 The influence of irrigation intervals and sweetpotato clones on sweetpotato weevil infestation (autumn transplanting 47 experiment)... 3.5.2 The influence of irrigation intervals and sweetpotato clones on sweetpotato weevil infestation (winter transplanting 48 experiment) 3.5.3 Sweetpotato weevil 48 6 management…………………………….……. 4. 49 RESULTS………………………………………………………….. 4.1 49 Survey………………………………………………………………. 4.2 Laboratory experiments (first season 49 2001/02)…………………… 4.2.1 Life history of sweetpotato weevil, Cylas puncticollis 49 Boheman….. 4.2.1.1 Duration of development of immature 49 stages………………………… 4.3 Field experiments (first season 55 2001/02)…………………………. 4.3.1 The influence of irrigation intervals and sweetpotato clones on 55 sweetpotato weevil infestation (autumn transplanting experiment)... 4.3.2 The influence of irrigation intervals and sweetpotato clones on 77 sweetpotato weevil infestation (winter transplanting experiment)… 4.3.3 Sweetpotato weevil 92 management……………………………….. …. 4.4 Laboratory experiments (second season 94 2002/03)…………………... 4.4.1 Life history of sweetpotato weevil, Cylas puncticollis 94 Boheman.….. 7 4.4.1.1Duration of development of immature 94 stages……………………… 4.4.1.2 Preoviposition 99 period………………………………………….. … 4.4.1.3 Oviposition 99 rate……………………………………………………. 4.4.1.4 Sex 99 ratio…………………………………………………………… 4.5 Field experiments (second season 99 2002/2003)………………………. 4.5.1 The influence of irrigation intervals and sweetpotato clones on sweetpotato weevil infestation (autumn transplanting 99 experiment) 4.5.2 The influence of irrigation intervals and sweetpotato clones on sweetpotato weevil infestation (winter transplanting 11 experiment) 7 4.5.3 Sweetpotato weevil 13 management………………………………..….. 4 5. 13 DISCUSSION…………………………………………………….. 7 … 5.1 Laboratory 13 experiments……………………………………………… 7 5.2 Field 13 experiments……………………………………………………. 9 5.2.1 Autumn transplanting season experiment (2001/2002) and 13 8 (2002/2003)………………………………………………………. 9 5.2.2 Winter transplanting season experiment (2001/2002) and 14 (2002/2003)………………………………………………………. 5 5.2.3 Sweetpotato weevil management(2001/2002) and 15 (2002/2003)…. 0 6. 15 REFERENCES…………………………………………………… 2 … Appendices 17 ………………………………………………………………. 0 9 AKNOWLEDGEMENTS I would like to express my profound gratitude and appreciation to my supervisor Prof. EL-Imam EL-Khidir for his interest, expert guidance and his relentless effort to make me produce an outstanding work. I wish to thank my co-supervisor Dr. Kamal Mowafi in particular for his advice during the course of this study, his friendly constructive comments have been highly valuable. The author is deeply indebted to a number of people who played key roles in the development of the research programme. First and foremost is Dr. Ali Khalafalla, Dr. Ensaf Sheihk Idris and Mr. Salah Muzamil, Agricultural Research Corporation, Shambat Station who provided me with sweetpotato clones and insecticides. My appreciation would be incomplete without recognizing Dr. Georg Georgen, International Institute of Tropical Agriculture (IITA), Biological Center for Africa/Insect Museum and Mr. Yakubu Adedigba Head, library and documentation services (IITA), Nigeria who sent for me valuable information and scientific papers at the early stage of the research. The financial contribution of the Third World Academy of Sciences (TWAS) Italy, International Potato Center (CIP) and PARAPACE-Kampala offices were of paramount importance in execution of an advance training on sweetpotato weevil in Uganda. Without assitance of Dr. Benson Odongo, Dr. Robert Mwanga, Mr. Charles Niringiye, Mrs. Justine Nanteza and all members of sweetpotato programme of Namulonge Agricultural and Animal 10 Production Research Institute (NAARI) Uganda, it would have been futile to expect fruitful training. My thanks and appreciation are extended to Dr. El-Tom EL-Sadig and DR. Abdul-Wahab Hassan Abdalla, Department of Crop Production Faculty of Agriculture University of Khartoum for their help in data analyzing. The author is appreciative to the University of Zalengei for funding the work. Needless to say, I would like to express my gratitude and appreciation to my family, my father, brother, sisters and in particular to my wife Itimad for boosting my morale during my stay aboard. A number of other people efforts, Abdul El Hameed Mohamed Ahamed, Sabah Mohamed Abdul-Wahab and Hanan Abdul El Rahaman who spent countless hours in typing the thesis are greatly aknowledged. Sincere thanks are also expressed to my colleagues who supported me in one way or anther. 11 ABSTRACT The biology of the developmental stages of the weevil, Cylas puncticollis Boheman a pest of sweetpotato storage roots was carried out for two years under laboratory conditions-at ambient room temperature and relative humidity and at a constant temperature of 30°C and 65% relative humidity (RH). Also field experiments were conducted for two years (2001/02 and 2002/03) to study the influence of irrigation intervals and type of sweetpotato clones on this weevil infestation. A trial to test some integrated pest management (IPM) techniques to improve sweetpotato yield and reduce weevil damage was also run. Average preoviposition period under room conditions was 4.33 ± 1.23 days. Eggs incubation period on average was similar under ambient room conditions and the controlled temperature and relative humidity experiment (3.00 ± 0.71and 3.00 ± 0.58 days-second year also gave close figures). The duration of the larval period under room conditions took less days (10.37 ±1.06 and 10.82 ± 1.57 days in the first and second year, respectively) than under constant temperature and RH conditions (13.83 ± 0.96 and 11.96 ± 0.76 days in the first and second year respectively); pupal period was also the same under ambient room conditions (3.15 ± 0.14 and 3.26 ± 0.27 days) and the constant temperature and RH (3.64 ± 0.22 and 3.98± 0.18 days). The methods of rearing (disturbed and undisturbed) was found to affect the developmental period seriously as there was a highly significant difference in the duration of the total life cycle of the weevil between the disturbed and the undisturbed rearing methods. Also, a significant difference with respect to the total life cycle existed between rearing 12 under room conditions and the constant temperature and RH conditions. The oviposition rate on average was 3.90 ± 1.67 eggs/female/day, sex ratio 1: 0.9 (female to male). Field experiments covered four seasons, two autumns and two winters in the years indicated to assess the effects of different irrigation intervals 7, 14, and 21 days gap and three types of clones TIS2544 (exotic), Baladi yellow (BY) and Baladi red (BR) (local) on the weevil infestation.