Kutywayo, Dumisani (2015) Studies of the mechanisms involved in host finding and mating behaviour of the African coffee white stem borer, Monochamus leuconotus (pascoe) (Cleoptera: Cerambycidae). PhD thesis, University of Greenwich.

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Abstract

The African coffee white stem borer, Monochamus leuconotus (Coleoptera: Cerambycidae) is a serious pest of Arabica coffee in Zimbabwe and other African countries. Very was known about the chemical ecology of M. leuconotus prior to the initiation of the studies described in this thesis. The objectives of this work were to investigate the mating behaviour in order to look for evidence of the existence of chemical interactions between conspecific beetles and host plants. Mating behaviour and daily activity patterns of adult M. leuconotus were characterised under laboratory and semifield conditions. Mating was initiated after the male encountered a searching female and touched her with antennae or tarsi. The activities of feeding, walking, mounting and copulation were mostly done during daylight hours with the exception of oviposition, which occurred at night. Laboratory bioassays conducted to determine whether contact pheromones played a role in mate recognition showed that males were able to complete the full sequence of behavioural activities involved in mating with both live and dead conspecific females. Males did not respond to dead females washed with hexane, and the responses could be partially restored by recoating the washed females with the hexane washings, indicating that cuticular hydrocarbons are important for recognition of sex and species. A laboratory bioassay was developed for evaluating the olfactory response of M. leuconotus to different cues. Females responded positively to coffee leaves, coffee bark scrapings and the synthetic male-specific compound of M. leuconotus dispensed in a sachet while males responded positively to coffee bark and to a combination of coffee leaves and the synthetic male-specific compound dispensed in a vial. Field trapping trials were conducted in Zimbabwe using live insect baits and the synthetic male-specific compound of M. leuconotus dispensed in polyethylene sachet and vials and different trap designs. Significant numbers of beetles were captured in traps baited with the male-specific compound, and numbers caught were further increased when certain host-plant volatiles were added, particularly (R)-(-)-linalool and methyl salicylate. Intercept panel traps and MK2 rat traps were effective in retaining insects caught. Floral surveys conducted around coffee fields to identify alternative host plants did not give conclusive evidence on the existence of alternative host plants although suspected coffee stem borer symptoms of attack were observed on previously reported alternative host plants. Feeding and oviposition studies suggested that female M. leuconotus feed mostly on Rubiaceae and preferred to lay eggs on Coffea arabica, G. ternifolia, V. infausta and K. venosa. The implications of the findings in relation to possible application of chemical ecology in management of M. leuconotus are discussed.

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	Coffee white stem borer; pheromone identification; Monochamus leuconotus (pascoe);
Subjects:	S Agriculture > SB Plant culture
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science Faculty of Engineering & Science > Natural Resources Institute
Last Modified:	28 Nov 2017 11:48
URI:	http://gala.gre.ac.uk/id/eprint/18211

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