Heterogeneity in virulence relationships between Cryptophlebia leucotreta granulovirus isolates and geographically distinct host populations: lessons from codling moth resistance to CpGV-M

Opoku-Debrah, John Kwadwo; Hill, Martin; Knox, Caroline; Moore, S.D.

doi:10.1007/s10526-016-9728-1

Cited by 9 publications

(6 citation statements)

References 18 publications

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“…Using a droplet-dose bioassay technique, developed by Pereirada-Conceicoa et al ( 2012), Opoku-Debrah (2012) and Opoku-Debrah et al (2016), determined average LD 50 and LD 90 values for Cryptogran™ against neonates from five different laboratoryreared populations of T. leucotreta to be 1.03 and 309.18 OBs/ larva. Consequently, to kill 50% of larvae in the field with a Cryptogran™ spray, application must be with a concentration and coverage that will enable larvae to ingest an average of 1.03 OBs each.…”

Section: Discussionmentioning

confidence: 99%

“…This is equivalent to an LD 83.7 and will thus kill an average of 84% of larvae in a population, if spray coverage is consistent and uniform across the surface of all fruit. This was determined by using mean mortalities per concentration for all five T. leucotreta populations (Opoku-Debrah et al 2016), to conduct a probit analysis in R, using the drm function (drc package), from which the R code ED(res1, c(LC values)) is used, to iteratively determine the LC/ LD value that would give 67. However, if the addition of molasses to the virus spray leads to greater feeding on the fruit surface, a greater ingestion of OBs and thus a higher spray efficacy can be expected.…”

Section: Discussionmentioning

confidence: 99%

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The addition of molasses to the Cryptophlebia leucotreta granulovirus formulation improves its efficacy against Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae), a pest of citrus in South Africa

Coombes,

Hilliar,

Moore

et al. 2024

Afr. Entomol.

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Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), commonly referred to as false codling moth, is an important pest of citrus in southern Africa. Given its quarantine status in markets to which a large portion of the fresh produce is exported, its management in citrus orchards is essential. This management typically follows a systems approach in which baculovirus-based biopesticides, such as Cryptogran™ (Betabaculovirus cryleucotreta), are considered an important component of pre-harvest control strategies. It has previously been demonstrated that adding molasses with Cryptogran™ improves field performance, further reducing the number of T. leucotreta infested fruit. However, the reason for this improvement was never determined. This study aimed to understand the role that molasses may have on the behaviour of T. leucotreta first instars under laboratory conditions, leading to this improved field efficacy, and to confirm conclusively if the addition of molasses to the virus formulation improved efficacy across a further six field trials. In the laboratory, larvae exposed to molasses-treated oranges at either a concentration of 0.25% or 0.50% moved around the surface of the oranges less and also penetrated the oranges less compared to larvae exposed to non-molasses-treated oranges. This suggested that molasses, as a phagostimulant, encouraged larval feeding quicker and longer. This will promote the uptake of the biopesticide infective units and is likely the reason for the recorded improved field efficacy of Cryptogran™ when combined with molasses across all six field trials compared to its application alone. These two sets of experiments confirm conclusively that the addition of molasses to the virus formulation improves its efficacy and should be standard practice in the industry.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

The addition of molasses to the Cryptophlebia leucotreta granulovirus formulation improves its efficacy against Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae), a pest of citrus in South Africa

Coombes,

Hilliar,

Moore

et al. 2024

Afr. Entomol.

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“…Consequently, it may be possible to determine whether there are differences in the UV sensitivity of different virus isolates of the same species and thus select the isolate that demonstrates the greatest potential for persistence in the field for development as a biopesticide. Several different isolates of CrleGV have been described [42][43][44][45], two of which are commercialised as biopesticides [46,47]. However, one of the other known isolates may prove more UV-tolerant and thus be a better candidate for development as a biopesticide.…”

Section: Discussionmentioning

confidence: 99%

Transmission Electron Microscopy Observation of Morphological Changes to Cryptophlebia Leucotreta Granulovirus following Ultraviolet Irradiation

et al. 2023

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Cryptophlebia leucotreta granulovirus (CrleGV), a double-stranded DNA virus (genus Betabaculovirus, family Baculoviridae), is highly infective to the citrus insect pest Thaumatotibia leucotreta. The South African isolate CrleGV-SA is formulated into a commercial biopesticide and registered for use in several countries. In South Africa, it is used as a biopesticide in a multi-faceted integrated pest management approach for citrus crops involving chemical and biological control methods. The virus nucleocapsid is surrounded and protected by an occlusion body (OB) composed of granulin protein in a crystalline matrix. Like all other baculoviruses, CrleGV is susceptible to ultraviolet (UV) radiation from sunlight. This reduces its efficacy as a biopesticide in the field and necessitates frequent respraying. UV damage to baculovirus biopesticides is detected by means of functional bioassays. However, bioassays do not give an indication of whether any structural damage has occurred that may contribute to functional loss. In this study, transmission electron microscopy (TEM) was used to observe damage to the OB and nucleocapsid (NC) of CrleGV-SA, following controlled UV irradiation in the laboratory to mimic field conditions. The resultant images were compared with images of non-irradiated CrleGV-SA virus. TEM images of irradiated CrleGV-SA samples revealed changes to the OB crystalline faceting, a reduction in the size of the OBs, and damage to the NC following UV exposure for 72 h.

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“…LT 50 and LT 90 values were estimated to be 4 days 22 h and 7 days 8 h, respectively. Opoku-Debrah et al [ 83 ] tested the virulence of five geographically distinct and two commercial isolates of CrleGV against larvae from five T. leucotreta laboratory cultures of different regional origins, in laboratory bioassays. They demonstrated that virulence is a very specific relationship between host and pathogen, showing that certain isolates were significantly more or less virulent against certain regionally distinct host populations.…”

Section: Baculovirusesmentioning

confidence: 99%

The History of Baculovirology in Africa

Moore

Jukes

2023

Viruses

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Baculovirology has been studied on the African continent for the development of insect virus-based biopesticides and, to a much lesser extent, vaccine production and delivery, since the 1960s. In this review, we focus only on baculoviruses as biopesticides for agricultural pests in Africa. At least 11 species of baculovirus have been discovered or studied on the African continent, some with several distinct isolates, with the objective in most cases being the development of a biopesticide. These include the nucleopolyhedroviruses of Helicoverpa armigera, Cryptophlebia peltastica, Spodoptera exempta, Spodoptera frugiperda, Spodoptera littoralis, and Maruca vitrata, as well as the granuloviruses of Cydia pomonella, Plutella xylostella, Thaumatotibia (Cryptophlebia) leucotreta, Choristoneura occidentalis, and Phthorimaea operculella. Eleven different baculovirus-based biopesticides are recorded as being registered and commercially available on the African continent. Baculoviruses are recorded to have been isolated, researched, utilised in field trials, and/or commercially deployed as biopesticides in at least 13 different African countries. Baculovirus research is ongoing in Africa, and researchers are confident that further novel species and isolates will be discovered, to the benefit of environmentally responsible agricultural pest management, not only in Africa but also elsewhere.

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Heterogeneity in virulence relationships between Cryptophlebia leucotreta granulovirus isolates and geographically distinct host populations: lessons from codling moth resistance to CpGV-M

Cited by 9 publications

References 18 publications

The addition of molasses to the Cryptophlebia leucotreta granulovirus formulation improves its efficacy against Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae), a pest of citrus in South Africa

The addition of molasses to the Cryptophlebia leucotreta granulovirus formulation improves its efficacy against Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae), a pest of citrus in South Africa

Transmission Electron Microscopy Observation of Morphological Changes to Cryptophlebia Leucotreta Granulovirus following Ultraviolet Irradiation

The History of Baculovirology in Africa

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