SUMMARYCydia pomonella granulosis viruses (CpGV) from seven different sources in Europe, America and New Zealand were compared by restriction enzyme analysis. Most samples were indistinguishable from the Mexican isolate (CpGV-M). Isolates from Russia (CpGV-R) and England (CpGV-E) showed small genotypic differences. CpGV-E was shown to be a mixture of two variants, E1 and E2. CpGV-E1 was indistinguishable from CpGV-M. A physical map of CpGV-M was constructed for the enzymes EcoRI, BamHI, HindIII, Sinai and ApaI. A comparison of fragment profiles allowed construction of maps for CpGV-R and CpGV-E2. Relative to CpGV-M, CpGV-R had a single deletion of 2.4 kbp and CpGV-E2 was modified in one area resulting in an additional EcoRI site, a shift in a BamHI site and in total about 1 kbp more DNA. The map was orientated by locating the granulin gene using the cloned granulin gene from Trichoplusia ni GV as a probe. There was no significant difference between the infectivities of the Mexican, Russian and English isolates for neonate larvae.

SUMMARYThe RNA genome segments of thirty-three isolates of cytoplasmic polyhedrosis viruses (CPVs) were examined by polyacrylamide gel electrophoresis. Major differences were observed in the gel profiles of the RNA segments from many of the viruses; differences which were reinforced by polyacrylamide gel electrophoresis of the virus structural proteins. As a result of these studies, a provisional classification scheme for CPVs is proposed, where viruses with similar RNA gel profiles are included within the same 'type', while isolates differing in the molecular weights of most, or all of the RNA segments are assigned to different types. Using this system, eleven distinct CPV types were recognized. All eleven CPV types, like reoviruses, probably contain ten segments of RNA with a total mol. wt. of approx. I5 × Io 6.

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SUMMARYVirus diseases have been reported from more than 800 species of insects and mites. Isolates of the baculovirus and cytoplasmic polyhedrosis virus groups have biological properties which should lead to their successful use as microbial control agents in integrated pest management programmes. These viruses infect the larval stages of many lepidopterous and hymenopterous pests, producing a chronic or lethal infection and the release of large quantities of relatively stable infective inclusion bodies (IBs). The IBs serve as the means by which the viruses are transmitted and persist outside the host. Younger larvae are more susceptible to infection than older stages, and this difference influences the timing of application and doses of virus needed for practical pest control. The high degree of host specificity of many isolates reduces their potential ecological hazard but also limits their use, particularly on crops where a complex of pests is established. Environmental persistence is also a limiting factor as virus is rapidly inactivated by ultra-violet light even when contained within IBs. The viruses persist for longer periods when transmitted within the host population, a feature of virus infections restricted to the insect gut.The practical use of insect viruses in horticulture and agriculture does not utilize their full epizootic potential, but takes advantage of their high pathogenicity and specificity. The baculoviruses of codling moth, andHeliothisspp. provide satisfactory pest control, but for their most cost-effective use it is important to determine the minimum dosage rates of virus required. It is encouraging that studies of the virus control ofPierisspp. have suggested that control achieved by the insecticidal use of a virus can be closely predicted from information on dosage-mortality responses, larval feeding rates and virus persistence. The stability of forest and grassland, and their high economic thresholds makes them ideal candidates for longer-term control. Viruses of the coconut rhinoceros beetle and european spruce sawfly provide examples of classical biological control where the viruses persist for long periods, are efficiently transmitted and act as natural regulators of their hosts. Virus control of pasture, and some forest, pests may be possible by manipulating enzootic viruses without the need for direct control measures. More frequently insecticidal applications are needed, providing control of limited duration which requires periodic ‘topping-up’.Few viruses are commercially-available; their selectivity and often small potential market, may limit industrial interest. However, improvements in virus production, formulation and a better understanding of virus epizootiology should lead to an increasing role for this group of insect pathogens in biological control.