title: Comparing the Use of Laboratory-Reared and Field-Collected Thaumatotibia leucotreta (Lepidoptera: Tortricidae) Larvae for Demonstrating Efficacy of Postharvest Cold Treatments in Citrus Fruit.
abstract: Some of South Africa's export markets require postharvest cold treatment of citrus fruit for phytosanitary risk mitigation for Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae). An alternative to a standalone cold treatment may be a reduced intensity cold treatment as a step in a systems approach. For cold treatment trials, large numbers of larvae are required. Due to recent dramatic improvement of T. leucotreta control in the field, sufficient naturally infested citrus fruit are no longer available. Artificial infestation of fruit is not viable due to rapid decay of the fruit. Consequently, it is necessary to use laboratory-reared T. leucotreta larvae in artificial diet. In trials, field-collected larvae from the Eastern Cape were at least as cold-tolerant as those from other regions. Larvae in Navel oranges showed the median level of susceptibility in a range of citrus types evaluated at 6°C, and their use in trials was considered acceptable due to their greater natural susceptibility to T. leucotreta infestation. We demonstrated that larvae at high density in artificial diet were at least as cold-tolerant as larvae at lower densities. When exposed to 2°C for 18 d or longer, larvae in artificial diet as used in the trials were at least as cold-tolerant as larvae in fruit. Very few surviving larvae from fruit completed development, with no subsequent generation. Consequently, it is considered justifiable to conduct cold-treatment trials with laboratory-reared T. leucotreta larvae in artificial diet without risk of overestimating the effect of cold on feral larvae in citrus fruit. [corrected]
authors.affiliation: Citrus Research International, PO Box 20285, Humewood 6013, Port Elizabeth, South Africa (seanmoore@cri.co.za; wk@cri.co.za) Department of Zoology and Entomology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa (sonnicavn@gmail.com) seanmoore@cri.co.za.
authors.forename: S D
authors.initials: SD
authors.lastname: Moore
authors.affiliation: Citrus Research International, PO Box 20285, Humewood 6013, Port Elizabeth, South Africa (seanmoore@cri.co.za; wk@cri.co.za).
authors.forename: W
authors.initials: W
authors.lastname: Kirkman
authors.affiliation: Department of Zoology and Entomology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa (sonnicavn@gmail.com).
authors.forename: S
authors.initials: S
authors.lastname: Albertyn
authors.affiliation: Citrus Research International, Department of Horticultural Sciences, Stellenbosch University, Victoria Street, Stellenbosch 7602, South Africa (vh@cri.co.za).
authors.forename: V
authors.initials: V
authors.lastname: Hattingh
mesh_terms: D000818:Animals; D002957:Citrus / Q000502:physiology*; D005638:Fruit / Q000502:physiology; D007300:Insect Control / Q000379:methods*; D007814:Larva / Q000254:growth & development / Q000502:physiology; D009036:Moths / Q000254:growth & development / Q000502:physiology*; D010572:Pest Control, Biological / Q000379:methods*; D013019:South Africa
keywords: South Africa; citrus type; false codling moth; larval density; region