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E T F Witkowski – One of the best experts on this subject based on the ideXlab platform.

  • interactions between a stem gall fly and a leaf spot pathogen in the biological control of Ageratina adenophora
    Biological Control, 2012
    Co-Authors: Lisa Buccellato, Marcus J Byrne, E T F Witkowski

    Abstract:

    Abstract Many biological control projects involve the release of multiple agents. Ageratina adenophora (crofton weed) has two agents, Procecidochares utilis , a stem gall fly, and Passalora Ageratinae , a leaf-spot fungal pathogen, released against it in South Africa. This study investigated whether both agents, individually or jointly, increased or decreased the impact on crofton weed under greenhouse conditions. Six-month-old plants were exposed to one of six treatments ( n  = 15 plants/treatment): control (no agents), pathogen-only, single-galled only, double-galled only, pathogen-single-galled, and pathogen-double-galled, all for a period of 6 months. Individually, both of the agents reduced stem height and percentage of live leaves, but there was no synergistic effect of the two agents together. Pathogen-double-galled stems had significantly fewer pathogen-infected leaves relative to the other pathogen-infected treatment stems, suggesting a negative interaction between the two agents on pathogen establishment. Pathogen infection did not affect the size of the galls. Double galling by the fly inhibited stem growth above the gall position on the stem. Crofton weed compensated for galling by increasing the number of sideshoots. The pathogen inhibited sideshoot growth, thereby curbing the plant’s ability to offset galling. Overall, there was an additive interaction between the two agents which enhances their usefulness as biocontrol agents of crofton weed.

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Stephen G Compton – One of the best experts on this subject based on the ideXlab platform.

  • impacts of a biocontrol agent on invasive Ageratina adenophora in southwest china friend or foe
    Biological Control, 2020
    Co-Authors: Chuan Yuan, Stephen G Compton, Qin Wang, Yan Chen, Lidan Zhang, Lu Tan, Jintian Yang, Mei Liu

    Abstract:

    Abstract Classical biological control of invasive plants depends on the introduction of host-specific natural enemies. Many natural enemies have provided successful control, but the impacts of herbivorous insects on their hosts are highly variable and context dependent. Under some circumstances, overcompensation can even occur, with plant reproduction temporarily increasing rather than decreasing in response to herbivory. The stem-galling fly Procecidochares utilis has been widely introduced to help control Ageratina adenophora, a globally significant weed, but its impact has been inconsistent and in places ineffective. Its galling is known to stimulate production of side branches in plants under laboratory conditions. We examined the abundance and impact of P. utilis at four A. adenophora sites of Southwest China that were invaded at different times and support different densities of the insect. Stems with galls were more likely to be branched and produced more capitula. Furthermore, seed numbers in capitula from galled and un-galled stems were similar, and galling resulted in only slightly reduced seed weights. However, the increase in above-ground vegetative biomass associated with branching resulted in less efficient capitulum production relative to vegetative growth. Clearly Procecidochares utilis is not providing effective biocontrol of Ageratina adenophora in Southwest China so far. In the long term, galled plants may display reduced competitive ability and lower lifetime reproductive success, but the short term increases in seed production it generates suggest it may be favouring its host’s range expansion. The fly has been a successful biocontrol agent in dry area of Hawii, so understanding the factors that determine its effectiveness represent a major challenge for the future.

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Lisa Buccellato – One of the best experts on this subject based on the ideXlab platform.

  • An insect-plant pathogen interaction between two biocontrol agents, the stem-gall fly and leaf-spot pathogen released against crofton weed, Ageratina adenophora
    , 2013
    Co-Authors: Lisa Buccellato

    Abstract:

    iv TABLE OF CONTENTS vi LIST OF FIGURES x LIST OF TABLES xv CHAPTER 1: INTRODUCTION 1-1 1.1 Background 1-2 1.2 Aims and objectives 1-6 1.2.1 Objectives of the laboratory and field trials 1-7 1.2.2 Objectives of the field surveys 1-7 1.3 Study species 1-9 1.3.1 Ageratina adenophora 1-9 1.3.2 Procecidochares utilis 1-11 1.3.3 Passalora Ageratinae 1-12 1.4 Multiple biocontrol agent releases 1-14 1.5 Post-release evaluations 1-17 1.6 Field sites 1-19 1.7 Structure of the thesis 1-21 CHAPTER 2: INTERACTIONS BETWEEN A STEM GALL FLY AND A LEAF-SPOT PATHOGEN IN THE BIOLOGICAL CONTROL OF Ageratina ADENOPHORA. 2-1 2.1 Abstract 2-2 2.2 Introduction 2-3 2.3 Material and methods 2-6 2.3.1 Laboratory trials 2-7 2.3.2 Data analysis 2-10 2.4 Results 2-10 2.4.1 Impact of AMISTAR ® on Ageratina adenophora growth … 2-10 2.4.2 Agent establishment and infection severity 2-10 2.4.3 Stem height 2-13 2.4.4 Stem growth above the oviposition site 2-13 2.4.5 Internode length above oviposition site 2-14

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  • interactions between a stem gall fly and a leaf spot pathogen in the biological control of Ageratina adenophora
    Biological Control, 2012
    Co-Authors: Lisa Buccellato, Marcus J Byrne, E T F Witkowski

    Abstract:

    Abstract Many biological control projects involve the release of multiple agents. Ageratina adenophora (crofton weed) has two agents, Procecidochares utilis , a stem gall fly, and Passalora Ageratinae , a leaf-spot fungal pathogen, released against it in South Africa. This study investigated whether both agents, individually or jointly, increased or decreased the impact on crofton weed under greenhouse conditions. Six-month-old plants were exposed to one of six treatments ( n  = 15 plants/treatment): control (no agents), pathogen-only, single-galled only, double-galled only, pathogen-single-galled, and pathogen-double-galled, all for a period of 6 months. Individually, both of the agents reduced stem height and percentage of live leaves, but there was no synergistic effect of the two agents together. Pathogen-double-galled stems had significantly fewer pathogen-infected leaves relative to the other pathogen-infected treatment stems, suggesting a negative interaction between the two agents on pathogen establishment. Pathogen infection did not affect the size of the galls. Double galling by the fly inhibited stem growth above the gall position on the stem. Crofton weed compensated for galling by increasing the number of sideshoots. The pathogen inhibited sideshoot growth, thereby curbing the plant’s ability to offset galling. Overall, there was an additive interaction between the two agents which enhances their usefulness as biocontrol agents of crofton weed.

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