ABSTRACT
The objective of this study was to determine the host status of commercially cultivated mango fruit, Mangifera indica L. (Anacardiaceae) to Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) in South Africa. T. leucotreta was monitored with parapheromone traps in mango orchards in Limpopo and Mpumalanga from 2007 to 2010. Fruit were inspected for the presence of T leucotreta eggs in mango orchards. Mango fruit of the cultivars 'Tommy Atkins', 'Kent', 'Keitt', and 'Sensation' were artificially infested with T. leucotreta eggs on the tree to determine if the larvae were able to develop in fruit. Mature fruit of these cultivars were harvested and were then exposed to T leucotreta eggs and the larval development monitored. Before harvest, fruit were inspected for natural infestations and a packhouse survey was conducted during the 2009-2010 season to determine if any infested fruit were present. T. leucotreta was present in all mango orchards where monitoring was done with traps but no eggs were found on the fruit, which suggests the presence of antixenosis. Development occurred in mature harvested fruit of all cultivars that had been exposed to T. leucotreta eggs. Depending on the cultivar, between 0 and 5.05% of immature fruit on the tree supported development and demonstrate antibiosis. No naturally infested fruit were found in the orchards or during the packhouse survey. Mango in South Africa is not a natural host for T. leucotreta. Mature mango fruit is an acceptable host for T. leucotreta larval development under artificial conditions. The latex plays an important role in the resistance mechanism of mango fruit to T. leucotreta.
Subject(s)
Host-Parasite Interactions , Mangifera/parasitology , Moths/physiology , Animals , Food Parasitology , Fruit/parasitology , Ovum , South AfricaABSTRACT
Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is pest of the avocado, Persea americana (Mill.) (Lauraceae), in South Africa and is regarded as a phytosanitary threat. The objective of this study was to develop a systems approach for T. leucotreta on 'Hass' avocado that will mitigate the pest risk. T. leucotreta males were monitored with pheromone traps, and numbers declined during the winter. Field studies indicated that most of eggs were laid during January in the Deerpark area, and during harvest, only 0.029 lesions produced live larvae. Survival of larvae in fruit infested on the tree and left to develop after harvest varied and depended on the time of infestation before harvest. Fruit firmness was measured and fifth instars were only present in soft fruit. Fenpropathrin and a granulovirus were effective in reducing the infestation levels. Bags used to cover fruit also reduced infestation levels. Lesions caused by T. leucotreta were visible from two weeks after infestation and fruit with lesions can be sorted. The mean infestation rate per orchard was 0.003 lesions per fruit which makes T. leucotreta on Hass amenable to the alternative treatment efficacy approach and maximum pest limit. In the case of T. leucotreta on Hass, poor host status, production, preharvest and postharvest measures were studied and low infestation levels were observed; all these elements would make a systems approach an option. Furthermore, inspection and certification as well as shipping and distribution measures could be added.
