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Title: A virus disease of leatherjackets
Author: Carter, John B.
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1971
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A Tipula iridescent virus (TIV) infection in the leatherjacket, Tipula oleracea (Linnaeus), was investigated in an attempt to assess whether TIV might be suitable as an agent for the biological control of leatherjackets. These insects are agricultural pests, and at present are controlled by chemicals which often affect many harmless and beneficial organisms. The investigations were mainly concerned with the mode of transmission of the virus and with effects of the environment upon the disease in the insect. Techniques for the assay of TIV were devised. A response-time method, which involves measuring incubation periods in TIV-injected larvae, did not give satisfactory estimates of TIV titres unless large numbers a larvae were used. There appears to be wide variability in the susceptibility of larvae to infection with TIV, which also limits the precision of TIV estimates by the usual LD50 method. Antibody-sensitised latex particles were used to detect and assay large concentrations of TIV. All stages in the life-cycle of T. oleracea, except the embryo, were found to be susceptible to TIV. Iridescence was observed in infected larvae in all four instars, in pupae, and in adults of both sexes. The transmission of TIV from infected to non-infected leatherjackets was demonstrated. It is suggested that TIV is transmitted mainly by non-infected larvae feeding upon the cadavers of infected larvae, and that a new generation becomes infected by feeding upon the cadavers of infected fourth-instar larvae from the previous generation. TIV-infected larvae were shown to excrete the virus, but not in quantities which are likely to serve as a source of infection, as leatherjackets only become infected per os if a large dose of yd./us is ingested. Inactivation of the virus by the gut fluids was considered as a possible reason for its low infectivity when ingested by the larvae, but the infectivity of a TIV suspension was found to be unaffected by larval gut fluids in vitro. It was shown that the rate of TIV replication is markedly affected by temperature, and it is suggested that the disease develops most rapidly during the warmest months of the year, with a very slow rate of development in winter.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available