Growth and development of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) on cultivated and wild graminaceous host plants

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ABSTRACT

The aim of this study was to identify a suitable trap crop for stem borers that could be used in a habitat management system in resource-poor maize fanning systems. A survey of wild host plants of stem borers was done in the Limpopo and Mpumalanga Provinces. Plant species belonging to Gramineae and Typhaceae were recorded as host plants to one or more species of stem borers. The stem borers found on host plants were Busseola fusca, Chilo partellus and Sesamia calamistis. The three grass species, Pennisetum purpureum (Napier grass), Hyparrhenia tamba (Blue thatching grass) and Panicum maximum (Guinea grass) were selected to study colonization of cultivated crops and the grasses by stem borers.
This was done under field conditions from the 199811999 to 2000/2001 seasons and the cultivated crops were maize, sorghum, sweet sorghum and pearl millet. Natural infestation by stem borers was allowed to take place. The incidence of whorl damage, dead heart and stem damage observed indicated that all plants were attacked by stem borers. Few larvae were found on the grasses compared to cultivated crops. Since H. tamba and P. purpureum were preferred for oviposition in the presence of maize and sorghum in laboratory bioassays the absence or low number of larvae was ascribed to poor survival of stem borers on the grasses. Host plant preference of C. partellus first instar larvae for cultivated and wild host plants was evaluated in two-choice and multiple-choice tests in laboratory bioassays.
Larval response to leaf discs of each host plant was also detennined under no-choice conditions. Results showed that the grasses were less preferred by neonate larvae compared to cultivated crops. This behavioural response could be exploited in a habitat management system since larvae would die without establishing on plants. Sweet sorghum land races were evaluated in the greenhouse for resistance to stem borers. The plants were artificially infested with first instar larvae of C. partellus and B. fusca. Pateletso possessed low levels of larval antixenosis and antibiosis for B. fusca and C. partellus. Multiple-choice tests were conducted to detennine oviposition preference for the landraces Mariri, Maatla, Motale, Pateletso, SA4481, and SA4479.
The greatest number of eggs were laid on SA4481. Two-choice experiments were conducted In the laboratory to determine ovipositional preference of B. fusca and C. partellus for maize and sweet sorghums. Results indicated that sweet sorghum plants compared to maize were not attractive enough for oviposition by both B. fusca and C. partellus moths to warrant their use as trap crops around maize fields . The role of forage sorghum and P. purpureum in the control of stem borers was evaluated in field trials with maize. While forage sorghum failed to reduce stem borer infestation in maize fields, infestation of the maize monocrop was higher than on maize crop surrounded by Napier grass. It was concluded that Napier grass holds promise as a trap crop for stem borers in maize farming systems.

GENERAL INTRODUCTION

Cereal crops are a vitally important source of food for humans and their livestock and contribute significantly to local and national economies (Smith & Wiedenmann 1997). Maize (Zea mays L.), sorghum (Sorghum bicolor (L.) Moench) and pearl millet (Pennisetum glaucum (L.) R. Br.) are three of the most important gramineous crops in Africa (Polaszek & Khan 1998). These species are grown over varied climatic zones and their yields vary between regions (Gahukar 1994). In Africa, the highest level of cereal production was recorded in 1988 with maize yielding 30 313 million tonnes, followed by sorghum with 15 280 million tonnes, and millet (13 330 million tonnes) which ranked fourth after wheat (13 630 million tonnes) (Chantereau & Nicou 1991).
Maize Maize originated in central America and by the 16th century was already cultivated in parts of West and southern Africa (Polaszek & Khan 1998). It is a staple food in most countries in southern Africa (Okech et al. 1994) and is used as both human and livestock food (Polaszek & Khan 1998). Although sub-Saharan African countries such as Kenya, South Africa, Tanzania, Ethiopia and Nigeria are principal producers of maize, South Africa is the only country that regularly exports maize (Polaszek & Khan 1998).
Maize in Africa is mostly grown by subsistence farmers and yields are generally low, averaging less than half of Asian and Latin American yields (Polaszek & Khan 1998). The average yield for industrialized countries is 6.2 t/ha, compared to only 2.5 t/ha for developing countries (Dowswell et al. 1996). In South Africa, maize has, since 1950, become one of the most important agricultural crops with a production exceeding ten million tons in favourable years (Van Rensburg et al. 1987). The average maize yield is 2.0 tlha in South Africa which is nonetheless low compared to 7.5 tlha, 7.1 tlha, and 7.8 tlha in developed countries in the United States of America (U.S.A), France, and Italy respectively (Dowswell et al. 1996) in which better technologies are employed.

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CONTENTS :

Abstract
Uittreksel
Acknowledgements
CHAPTER 1: General introduction
CHAPTER 2: Wild host plants and their stem borers (Lepidoptera) in the Limpopo and northern Mpumalanga Provinces
- Abstract
- Introduction
- Material, methods and study sites
- Results
- Discussion
- References
- Tables
- Figures
CHAPTER 3: Colonization of cultivated and wild graminaceous host plants by Busseolafusca Fuller (Lepidoptera: Noctuidae) and Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) under field conditions
- Abstract
- Introduction
- Methods and study sites
- Results
- Discussion
- References
- Tables
- Figures
CHAPTER 4: Oviposition preference of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) for cultivated and wild graminaceous host plants
- Abstract
- Introduction
- Material and methods
- Results
- Discussion
- References
- Tables
- Figures
CHAPTER 5: Preference of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) larvae for cultivated and wild graminaceous host plants
- Abstract
- Introduction
- Material and methods
- Results
- Discussion
- References
- Tables
- Figures
CHAPTER 6: Growth and development of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) on cultivated and wild graminaceous host plants
- Abstract.
- Introduction
- Material and methods
- Results
- Discussion
- References
- Tables
- Figures
CHAPTER 7: Leaf feeding resistance and oviposition preference of Busseola fusea Fuller (Lepidoptera: Noctuidae) and Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) for sweet sorghum (Sorghum hieolor) land races
- Abstract.
- Introduction
- Material and methods
- Results
- Discussion
- References
- Tables
- Figures
CHAPTER 8: Field evaluation of forage sorghum (Sorghum hieolor x S sudanensis) and Pennisetum purpureum (Napier grass) as trap crops in a habitat management system
- Abstract
- Introduction
- Material and methods
- Results
- Discussion
- References
- Tables
- Figures
CHAPTER 9: Summary