Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The export of South African fruit to some of its biggest international markets may be rejected
if the phytosanitary pest, Phlyctinus callosus (Coleoptera: Curculionidae) is found in fruit
consignments. An alternative to methyl bromide fumigation is needed and one of the most
promising of the alternative treatments is phytosanitary irradiation as it is environmentally
friendly, does not leave residues on food or in the environment and it is effective against a
wide variety of insects.
Field-collected weevils were treated with five doses of gamma irradiation (5, 10, 20, 40 and
80 Gy) and the fecundity and fertility of mating crosses of treated males and females with
treated and untreated individuals of the opposite sex, were determined to evaluate the effect
on P. callosus reproductive ability post-treatment. Results indicated that irradiation treatment
did not affect fecundity, but fertility was significantly affected, decreasing as the irradiation
dose increased. Females were more susceptible to the irradiation treatment than males, and
after treatment with 80 Gy, eggs laid by females and mated with either treated or untreated
males, did not hatch. A generic dose of 400 Gy for all insect pests except tephritid fruit flies
and pupae and adult Lepidoptera is currently approved by USDA-APHIS (United States
Department of Agriculture – Animal and Plant Health Inspection Services) for use on certain
commodities. Results from the present study support the development of a species-specific
dose for P. callosus, as well as the development of a group generic dose for the Curculionidae
that is lower than 400 Gy. Effective phytosanitary irradiation treatments are only feasible if
the treatment does not adversely affect fruit quality and the marketability of export fruit.
Therefore, an investigation of the effects of irradiation disinfestations treatments on the
quality of the new pluot cultivar, ‘Flavor Fall’ was made. Packed cartons were treated with
three doses of gamma irradiation: 400 Gy, 900 Gy and 1400 Gy. After treatment fruit
underwent a PD 7 dual temperature cold storage regime for 42 days and a shelf-life simulation for 7 days. The impact of insect-proof bags, sometimes required by importing
countries to keep insects off packaged fruit, was also investigated. Respiration rate of the fruit
was measured throughout and fruit quality evaluations were done after cold storage and after
shelf-life. The results indicated that quality parameters measured at the end of cold storage,
which would be after the fruit arrives at the export markets, were above the minimum
standards for overseas markets. Gel breakdown was unacceptably high after the higher
temperature exposure of shelf-life for fruit treated with the 900 and 1400 Gy doses. The
insect-proof bags reduced shrivel, but resulted in higher incidence of gel breakdown. The use
of irradiation, together with the use of the insect-proof bag, has potential as an alternative
postharvest mitigation treatment for plums.
Lastly, an investigation into potential rearing methods for P. callosus, including
recommendation for the future, was made as the availability of a sustainable rearing method
that ensures a consistent supply of high quality P. callosus adults would enable continuous
research with greater numbers of this pest. The information generated in this study provides a
greater understanding of the radiation biology of, not only this curculionid species, but the
Curculionidae as a group, and is valuable in advancing the development of alternative
postharvest control measures against this phytosanitary pest. / AFRIKAANSE OPSOMMING: Suid Afrikaanse vrugte uitvoere na van die grootste internasionale markte mag weg gewys
word as die fitosanitêre pes, Phlyctinus callosus (Coleoptera: Curculionidae) in die
versending gevind word. ‘n Alternatief vir metiel bromied beroking word benodig en een van
die mees belowende alternatiewe behandelings is fitosanitêre bestraling aangesien dit
omgewings vriendelik is, nie residue op kos of in die omgewing los nie, en effektief is teen ‘n
wye verskeidenheid van insekte.
Veldversamelde kalanders is behandel met vyf dosisse gamma bestraling (5, 10, 20, 40 en 80
Gy) waarna die vrugbaarheid van paringskruisings bepaal is deur kruisings tussen behandelde
manlike en vroulike kalanders met behandelde en nie-behandelde individue van die
teenoorgestelde geslag te maak, en so die na-behandelings effek op die voortplantings
vermoeë van P. callosus te evalueer. Die resultate het getoon dat die bestralings behandeling
geen invloed gehad het op die hoeveelheid eiers wat gelê is nie, maar dat die uitbroei van
eiers aanduidend geaffekteer is deur die behandeling. Die hoeveelheid eiers wat uitgebroei
het, het minder geraak soos die bestralings behandeling toegeneem het. Vroulike kalanders
was meer sensitief vir die behandeling en na 80 Gy, of hul gekruis is met behandelde of niebehandelde
mannetjies, het geen eiers uitgebroei nie. ‘n Generiese dosis van 400 Gy vir alle
insekte, uitsluitend tephritiese vrugte vlieë en papies en volwasse Lepidoptera is huidiglik
goedgekeur deur die USDA-APHIS (United States Department of Agriculture – Animal and
Plant Health Inspection Services) vir sekere kommoditeite. Die resultate van die huidige
studie ondersteun die ontwikkeling van ‘n spesie-spesifieke dosis vir P. callosus, so ook die
ontwikkeling van ‘n generiese groep dosis vir Curculionidae wat laer as 400 Gy is.
Effektiewe fitosanitêre bestralings behandeling is slegs moontlik indien die behandelings
dosis nie nadelig vir vrugkwaliteit en die bemarking van uitvoer vrugte is nie. Dus is die effek wat bestralings bestryding behandeling op die kwaliteit van ‘n nuwe pluot
kultivar, ‘Flavor Fall’ ondersoek. Vrugte verpak in kartonne is met drie dosisse gamma
bestraling behandel: 400 Gy, 900 Gy en 1400 Gy. Na behandeling is die vrugte deur ‘n PD 7
dubbel temperatuur koelopbergings regime van 42 dae en rak-lewe simulasie vir 7 dae gesit.
Die impak van insek-bestande sakke wat insekte van die verpakte vrugte weg hou en soms
deur invoerende lande ‘n vereiste is, is ook ondersoek. Respirasie tempo van die vrugte is
getoets en vrugkwaliteit evaluasies is gedoen na koelopberging en rak-lewe. Die resultate het
getoon dat die kwaliteits maatstawwe wat getoets is na koelopberging (wat tipies is wanneer
die vrugte by die uitvoer mark arriveer), almal bo die minimum standaarde van die uitvoer
markte was. Gel-afbraak was onaanvaarbaar hoog na blootstelling aan die hoër temperature
tydens rak-lewe vir vrugte wat behandel is met 900 en 1400 Gy. Die insek-bestande sakke het
verrimpeling verminder, maar die voorkoms van gel-afbraak vermeerder. Die gebruik van
bestraling, tesame met die insek-bestande sakke, het potensiaal as alternatiewe na-oes
behandeling vir pruime.
Laastens is ‘n ondersoek ingestel vir moontlike teeltegnieke vir P. callosus en aanbevelings
gemaak vir toekomstike studies. Die beskikbaarheid van ‘n volhoubare teeltegniek wat
konstante, hoë kwaliteit P. colossus individue verskaf sal aaneenlopende navorsing met
groter getalle van die pes moontlik maak. Die inligting wat deur hierdie studie gegenereer is
help om die bestralings biologie, nie net van hierdie curculionid spesie nie, maar die
Curculionidae as ‘n groep te verstaan, en is kosbaar in die bevordering van ontwikkeling van
alternatiewe na-oes beheer meganismes teen hierdie fitosanitêre pes.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/85709 |
| Date | 12 1900 |
| Creators | Duvenhage, Andries J. |
| Contributors | Johnson, Shelley, Jooste, Mariana, Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Format | xii, 100 p. : ill. |
| Rights | Stellenbosch University |
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