Enhancing foraging behaviour of stemborer parasitoids: role of a non-host plant Melinis minutiflora

L.S. Gohole

Research output: Thesisinternal PhD, WUAcademic

Abstract

Stemborers are major pests of maize and sorghum in tropical Africa. Various management approaches to stemborer control are being sought with emphasis on those that are environmentally sound, sustainable and economically feasible. Studies reported in this thesis were conducted to explore the potential of employing habitat management techniques to enhance the effectiveness of stemborer parasitoids. Emphasis was placed on the chemical and behavioural ecology of stemborer parasitoids in a diversified system that consisted of the stemborer host plants, maize and sorghum, stemborers and a non-host plant, molasses grass ( Melinis minutiflora ).

Olfactometric studies on the stimuli involved in long-range foraging behaviour of the parasitoids Cotesia sesamiae and Dentichasmias busseolae revealed that host plant volatiles play a major role in guiding searching parasitoids to habitats that harbour their hosts. Volatiles from herbivore-injured plants were the most attractive. Sorghum was more attractive to the parasitoids than maize. Molasses grass volatiles were attractive to C. sesamiae but repellent to D. busseolae . Combining host plants and molasses grass did not have an additive effect of increasing the response of the parasitoids. Local growth conditions influenced the volatile blend produced by molasses grass grown in two different locations in Kenya, Thika and Mbita. This was manifested by their differential attractiveness to C. sesamiae . Dentichasmias busseolae did not discriminate between host species at a distance based on the volatiles released by infested host plants. Headspace analyses of volatiles emitted by uninfested and infested host plants and molasses grass grown at Thika and Mbita, revealed qualitative differences in their compositions. Infested host plants released a richer volatile blend than the uninfested host plants. Most of the compounds identified in the herbivore-injured plants were previously reported to play a role in parasitoid recruitment. Molasses grass from Thika had a number of its identified compounds that were similar to some in the blend of infested host plants. These compounds might have played a role in attracting C. sesamiae . Molasses grass from Mbita had very few compounds common to the other plants.

Semi-field studies on the close-range searching behaviour of C. sesamiae showed that the parasitoid was not arrested by molasses grass although the grass had previously been demonstrated to be attractive to this parasitoid. The presence of molasses grass in a patch with host plants did not interfere with the foraging behaviour of D. busseolae . Both parasitoids recognized host plants at close range and were arrested on infested host plants where they spent most of their time engaged in host searching activities. Field studies showed that stemborer densities were lower in the intercrop than in the monocrop, while diversifying the habitat with molasses grass had no effect on stemborer parasitism. Larval and pupal parasitism was 2.1 and 11.0% in the monocrop compared to 2.0 and 9.8% in the intercrop.

The main conclusion of this thesis is that intercropping maize or sorghum with molasses grass does not enhance the foraging behaviour of stemborer parasitoids. Molasses grass seems to be of more importance to the herbivore than the parasitoids. Hence, to clearly understand why stemborer densities were lower in the intercrop than the monocrop, future studies should focus on the interrelations between molasses grass, stemborers and host plants.

LanguageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Vet, Louise, Promotor
Award date18 Mar 2003
Place of Publication[S.I.]
Publisher
Print ISBNs9058088006
Publication statusPublished - 2003

Fingerprint

Melinis minutiflora
parasitoids
foraging
host plants
Cotesia sesamiae
Sorghum (Poaceae)
herbivores
corn
parasitism
searching behavior
host seeking
habitat conservation

Keywords

  • stem borers
  • parasitoids
  • cotesia
  • foraging
  • animal behaviour
  • melinis minutiflora
  • host plants
  • habitats
  • diversity
  • vegetation management
  • trophic levels

Cite this

@phdthesis{6ed075eb390a4bc286c6a99b83e2a478,
title = "Enhancing foraging behaviour of stemborer parasitoids: role of a non-host plant Melinis minutiflora",
abstract = "Stemborers are major pests of maize and sorghum in tropical Africa. Various management approaches to stemborer control are being sought with emphasis on those that are environmentally sound, sustainable and economically feasible. Studies reported in this thesis were conducted to explore the potential of employing habitat management techniques to enhance the effectiveness of stemborer parasitoids. Emphasis was placed on the chemical and behavioural ecology of stemborer parasitoids in a diversified system that consisted of the stemborer host plants, maize and sorghum, stemborers and a non-host plant, molasses grass ( Melinis minutiflora ).Olfactometric studies on the stimuli involved in long-range foraging behaviour of the parasitoids Cotesia sesamiae and Dentichasmias busseolae revealed that host plant volatiles play a major role in guiding searching parasitoids to habitats that harbour their hosts. Volatiles from herbivore-injured plants were the most attractive. Sorghum was more attractive to the parasitoids than maize. Molasses grass volatiles were attractive to C. sesamiae but repellent to D. busseolae . Combining host plants and molasses grass did not have an additive effect of increasing the response of the parasitoids. Local growth conditions influenced the volatile blend produced by molasses grass grown in two different locations in Kenya, Thika and Mbita. This was manifested by their differential attractiveness to C. sesamiae . Dentichasmias busseolae did not discriminate between host species at a distance based on the volatiles released by infested host plants. Headspace analyses of volatiles emitted by uninfested and infested host plants and molasses grass grown at Thika and Mbita, revealed qualitative differences in their compositions. Infested host plants released a richer volatile blend than the uninfested host plants. Most of the compounds identified in the herbivore-injured plants were previously reported to play a role in parasitoid recruitment. Molasses grass from Thika had a number of its identified compounds that were similar to some in the blend of infested host plants. These compounds might have played a role in attracting C. sesamiae . Molasses grass from Mbita had very few compounds common to the other plants.Semi-field studies on the close-range searching behaviour of C. sesamiae showed that the parasitoid was not arrested by molasses grass although the grass had previously been demonstrated to be attractive to this parasitoid. The presence of molasses grass in a patch with host plants did not interfere with the foraging behaviour of D. busseolae . Both parasitoids recognized host plants at close range and were arrested on infested host plants where they spent most of their time engaged in host searching activities. Field studies showed that stemborer densities were lower in the intercrop than in the monocrop, while diversifying the habitat with molasses grass had no effect on stemborer parasitism. Larval and pupal parasitism was 2.1 and 11.0{\%} in the monocrop compared to 2.0 and 9.8{\%} in the intercrop.The main conclusion of this thesis is that intercropping maize or sorghum with molasses grass does not enhance the foraging behaviour of stemborer parasitoids. Molasses grass seems to be of more importance to the herbivore than the parasitoids. Hence, to clearly understand why stemborer densities were lower in the intercrop than the monocrop, future studies should focus on the interrelations between molasses grass, stemborers and host plants.",
keywords = "melinis minutiflora, parasito{\"i}den, foerageren, diergedrag, habitats, vegetatiebeheer, waardplanten, cotesia, diversiteit, trofische graden, waardplanten van plantenplagen, stem borers, parasitoids, cotesia, foraging, animal behaviour, melinis minutiflora, host plants, habitats, diversity, vegetation management, trophic levels",
author = "L.S. Gohole",
note = "WU thesis 3358",
year = "2003",
language = "English",
isbn = "9058088006",
publisher = "S.n.",
school = "Wageningen University",

}

Gohole, LS 2003, 'Enhancing foraging behaviour of stemborer parasitoids: role of a non-host plant Melinis minutiflora', Doctor of Philosophy, Wageningen University, [S.I.].

Enhancing foraging behaviour of stemborer parasitoids: role of a non-host plant Melinis minutiflora. / Gohole, L.S.

[S.I.] : S.n., 2003. 140 p.

Research output: Thesisinternal PhD, WUAcademic

TY - THES

T1 - Enhancing foraging behaviour of stemborer parasitoids: role of a non-host plant Melinis minutiflora

AU - Gohole, L.S.

N1 - WU thesis 3358

PY - 2003

Y1 - 2003

N2 - Stemborers are major pests of maize and sorghum in tropical Africa. Various management approaches to stemborer control are being sought with emphasis on those that are environmentally sound, sustainable and economically feasible. Studies reported in this thesis were conducted to explore the potential of employing habitat management techniques to enhance the effectiveness of stemborer parasitoids. Emphasis was placed on the chemical and behavioural ecology of stemborer parasitoids in a diversified system that consisted of the stemborer host plants, maize and sorghum, stemborers and a non-host plant, molasses grass ( Melinis minutiflora ).Olfactometric studies on the stimuli involved in long-range foraging behaviour of the parasitoids Cotesia sesamiae and Dentichasmias busseolae revealed that host plant volatiles play a major role in guiding searching parasitoids to habitats that harbour their hosts. Volatiles from herbivore-injured plants were the most attractive. Sorghum was more attractive to the parasitoids than maize. Molasses grass volatiles were attractive to C. sesamiae but repellent to D. busseolae . Combining host plants and molasses grass did not have an additive effect of increasing the response of the parasitoids. Local growth conditions influenced the volatile blend produced by molasses grass grown in two different locations in Kenya, Thika and Mbita. This was manifested by their differential attractiveness to C. sesamiae . Dentichasmias busseolae did not discriminate between host species at a distance based on the volatiles released by infested host plants. Headspace analyses of volatiles emitted by uninfested and infested host plants and molasses grass grown at Thika and Mbita, revealed qualitative differences in their compositions. Infested host plants released a richer volatile blend than the uninfested host plants. Most of the compounds identified in the herbivore-injured plants were previously reported to play a role in parasitoid recruitment. Molasses grass from Thika had a number of its identified compounds that were similar to some in the blend of infested host plants. These compounds might have played a role in attracting C. sesamiae . Molasses grass from Mbita had very few compounds common to the other plants.Semi-field studies on the close-range searching behaviour of C. sesamiae showed that the parasitoid was not arrested by molasses grass although the grass had previously been demonstrated to be attractive to this parasitoid. The presence of molasses grass in a patch with host plants did not interfere with the foraging behaviour of D. busseolae . Both parasitoids recognized host plants at close range and were arrested on infested host plants where they spent most of their time engaged in host searching activities. Field studies showed that stemborer densities were lower in the intercrop than in the monocrop, while diversifying the habitat with molasses grass had no effect on stemborer parasitism. Larval and pupal parasitism was 2.1 and 11.0% in the monocrop compared to 2.0 and 9.8% in the intercrop.The main conclusion of this thesis is that intercropping maize or sorghum with molasses grass does not enhance the foraging behaviour of stemborer parasitoids. Molasses grass seems to be of more importance to the herbivore than the parasitoids. Hence, to clearly understand why stemborer densities were lower in the intercrop than the monocrop, future studies should focus on the interrelations between molasses grass, stemborers and host plants.

AB - Stemborers are major pests of maize and sorghum in tropical Africa. Various management approaches to stemborer control are being sought with emphasis on those that are environmentally sound, sustainable and economically feasible. Studies reported in this thesis were conducted to explore the potential of employing habitat management techniques to enhance the effectiveness of stemborer parasitoids. Emphasis was placed on the chemical and behavioural ecology of stemborer parasitoids in a diversified system that consisted of the stemborer host plants, maize and sorghum, stemborers and a non-host plant, molasses grass ( Melinis minutiflora ).Olfactometric studies on the stimuli involved in long-range foraging behaviour of the parasitoids Cotesia sesamiae and Dentichasmias busseolae revealed that host plant volatiles play a major role in guiding searching parasitoids to habitats that harbour their hosts. Volatiles from herbivore-injured plants were the most attractive. Sorghum was more attractive to the parasitoids than maize. Molasses grass volatiles were attractive to C. sesamiae but repellent to D. busseolae . Combining host plants and molasses grass did not have an additive effect of increasing the response of the parasitoids. Local growth conditions influenced the volatile blend produced by molasses grass grown in two different locations in Kenya, Thika and Mbita. This was manifested by their differential attractiveness to C. sesamiae . Dentichasmias busseolae did not discriminate between host species at a distance based on the volatiles released by infested host plants. Headspace analyses of volatiles emitted by uninfested and infested host plants and molasses grass grown at Thika and Mbita, revealed qualitative differences in their compositions. Infested host plants released a richer volatile blend than the uninfested host plants. Most of the compounds identified in the herbivore-injured plants were previously reported to play a role in parasitoid recruitment. Molasses grass from Thika had a number of its identified compounds that were similar to some in the blend of infested host plants. These compounds might have played a role in attracting C. sesamiae . Molasses grass from Mbita had very few compounds common to the other plants.Semi-field studies on the close-range searching behaviour of C. sesamiae showed that the parasitoid was not arrested by molasses grass although the grass had previously been demonstrated to be attractive to this parasitoid. The presence of molasses grass in a patch with host plants did not interfere with the foraging behaviour of D. busseolae . Both parasitoids recognized host plants at close range and were arrested on infested host plants where they spent most of their time engaged in host searching activities. Field studies showed that stemborer densities were lower in the intercrop than in the monocrop, while diversifying the habitat with molasses grass had no effect on stemborer parasitism. Larval and pupal parasitism was 2.1 and 11.0% in the monocrop compared to 2.0 and 9.8% in the intercrop.The main conclusion of this thesis is that intercropping maize or sorghum with molasses grass does not enhance the foraging behaviour of stemborer parasitoids. Molasses grass seems to be of more importance to the herbivore than the parasitoids. Hence, to clearly understand why stemborer densities were lower in the intercrop than the monocrop, future studies should focus on the interrelations between molasses grass, stemborers and host plants.

KW - melinis minutiflora

KW - parasitoïden

KW - foerageren

KW - diergedrag

KW - habitats

KW - vegetatiebeheer

KW - waardplanten

KW - cotesia

KW - diversiteit

KW - trofische graden

KW - waardplanten van plantenplagen

KW - stem borers

KW - parasitoids

KW - cotesia

KW - foraging

KW - animal behaviour

KW - melinis minutiflora

KW - host plants

KW - habitats

KW - diversity

KW - vegetation management

KW - trophic levels

M3 - internal PhD, WU

SN - 9058088006

PB - S.n.

CY - [S.I.]

ER -