Host plant, Aphis gossypii Glover (Hemiptera: Aphididae) and Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae) interactions: potential for aphid biological control in cotton cropping systems

Jamie Hopkinson (2010). Host plant, Aphis gossypii Glover (Hemiptera: Aphididae) and Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae) interactions: potential for aphid biological control in cotton cropping systems PhD Thesis, School of Biological Sciences, The University of Queensland.

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Author Jamie Hopkinson
Thesis Title Host plant, Aphis gossypii Glover (Hemiptera: Aphididae) and Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae) interactions: potential for aphid biological control in cotton cropping systems
School, Centre or Institute School of Biological Sciences
Institution The University of Queensland
Publication date 2010-09
Thesis type PhD Thesis
Supervisor Myron Zalucki
Dave Murray
Total pages 136
Total colour pages 4
Total black and white pages 132
Subjects 07 Agricultural and Veterinary Sciences
Abstract/Summary Cotton aphid, Aphis gossypii is a polyphagous pest of various crops worldwide. In Australia this introduced aphid is considered a major pest of cotton. The adoption of transgenic cotton (Bollgard® II) has transformed the Australian cotton industry and led to new opportunities in IPM, including greater use of biological control for pests like A. gossypii. The aphid parasitoid, Lysiphlebus testaceipes has a broad host range including A. gossypii, but little is known of it potential for control of A. gossypii. To test the concept of using alternative hosts as a source of parasitoids in an intercropping environment to improve A. gossypii control, aspects of L. testaceipes biology where investigated, including adult diet, host acceptance behaviour, and the effects of host quality and switching behaviour on levels of parasitism. Effect of adult diet on wasp fitness was tested by offering L. testaceipes various diets (water, dilute honey, aphid honeydew or buckwheat nectar) then recording lifespan, egg load and parasitism. Availability of dietary carbohydrates improved L. testaceipes fitness; both lifespan and potential fecundity increased when carbohydrates were available. Potential fecundity was correlated with body size suggesting teneral reserves are important in egg maturation. Fitness of wasps fed nectar of flowering buckwheat was not different to wasp fed aphid honeydew. In a glasshouse experiment parasitism of A. gossypii was not increased when flowering buckwheat was available. Provision of additional sources of carbohydrates such as food sprays and companion planting of flowering plants like buckwheat appears unlikely to increase parasitism of A. gossypii by L. testaceipes. Host acceptance behaviour of L. testaceipes in laboratory trials was observed when offered A. gossypii and Aphis craccivora Koch on cotton, hibiscus or mungbean. Lysiphlebus testaceipes accepted more A. craccivora than A. gossypii and more aphids on mungbean than on cotton. Lysiphlebus testaceipes has a preference for A. craccivora and mungbean compared to A. gossypii and cotton. The effect of developmental stage on host acceptance was studied by observing L. testaceipes with 2nd, 4th and adult stages of A. gossypii or A. craccivora. Lysiphlebus testaceipes had a preference for older (4th and adult) stages of development over a younger (2nd) instar. Observations of host acceptance behaviour revealed that A. gossypii cornicle secretion is an effective deterrent, capable of disabling L. testaceipes and thus preventing it from making further attempts at parasitising hosts. This effect was not observed in A. craccivora. The quality of A. gossypii and A. craccivora as hosts was investigated by exposing each developmental stage of both species to L. testaceipes. Development in A. craccivora produced a wasp of higher fitness compared to A. gossypii in terms of shorter development time, larger body size, longer lifespan and higher potential fecundity. Aphid instar parasitised had a significant effect on wasp fitness; in A. craccivora older instars produced wasps with higher fitness compared to younger instars. Wasps that developed in older instars completed development faster, were bigger and had higher potential fecundity. Effect of host plant on parasitism was studied by recording parasitism of A. gossypii on cotton and cucumber. Parasitism was higher on cotton than cucumber. Fitness of wasps in terms of egg load and body size was higher for wasps from hosts parasitised on cotton compared to cucumber. Host switching of L. testaceipes was studied in a glasshouse experiment, where relative abundance of A. gossypii and A. craccivora was controlled. Lysiphlebus testaceipes demonstrated no switching response to species abundance; parasitism was always higher on A. craccivora than A. gossypii. Higher parasitism of A. craccivora may be due to the higher quality of A. craccivora as a host compared to A. gossypii and/or better defence in A. gossypii. Lysiphlebus testaceipes does not appear to be a suitable candidate for biological control of A. gossypii. Aphis gossypii host quality for L. testaceipes is poor, resulting in small populations of wasps with slowed development and low fitness. Aphis gossypii defence against parasitism is high making it difficult for L. testaceipes to parasitise large numbers of A. gossypii. Even when A. gossypii is relatively abundant it is not readily accepted as a host.
Keyword Cotton
Aphis gossypii
Aphis craccivora
Lysiphlebus testaceipes
Biological Control
host quality
Additional Notes colour pages; 17,20,37,47

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Created: Wed, 29 Jun 2011, 12:38:38 EST by Mr Jamie Hopkinson on behalf of Library - Information Access Service