Biocontrol Science and Technology (2009) 19, 887-898

Jorge Toledo, Trevor Williams, Concepción Pérez, Pablo Liedo, Javier F. Valle and Jorge E. Ibarra (2009)
Abiotic factors affecting the infectivity of Steinernema carpocapsae (Rhabditida: Steinernematidae) on larvae of Anastrepha obliqua (Diptera: Tephritidae)
Biocontrol Science and Technology 19 (9), 887-898
Abstract: The effects of soil depth, soil type and temperature on the activity of the nematode Steinernema carpocapsae (Filipjev) were examined using larvae of the West Indian fruit fly, Anastrepha obliqua (Macquart). Bioassays involved applying infective juveniles (IJs) to the surface of sterilized sand in PVC tubes previously inoculated with fly larvae of two ages. The 50% lethal concentration (LC₅₀) values estimated for 6-day-old larvae were 9, 20 and 102 IJs/cm² in tubes containing 2, 5 and 8 cm depth of sand, respectively, whereas for 8-day-old larvae, LC₅₀ values were 16, 40 and 157 IJs/cm², respectively. The effect of soil texture on the activity of S. carpocapsae was tested by applying the corresponding LC₅₀ concentrations of nematodes to sand, sand-clay and loamy-sand soils. For 6-day-old larvae, soil type had a highly significant effect on infection with the highest percentages of infection observed in the sand-clay mixture (60-82% depending on depth) compared to 45-64% infection in sand and 23-30% infection in loamy-sand soil. A very similar pattern was observed in 8-day-old larvae except that infection rates were significantly lower than in younger larvae. There was a significant interaction between soil type and soil depth. The effect of three temperatures (19, 25 and 30°C) on infection was examined in sand-clay soil. The infectivity of S. carpocapsae was affected by temperature and soil depth and by the interaction of these two factors. Response surface analysis applied to second order multiple linear regression models indicated that the optimal temperature for infection of larvae of both ages was ~26°C, at a depth of 7.9 cm for 6-day-old larvae and <2 cm for 8-day-old larvae, resulting in a predicted 91.4% infection of 6-day-old larvae and 61.2% infection of 8-day-old larvae. These results suggest that S. carpocapsae may have the potential to control fruit fly pests in tropical ecosystems with warm temperatures and high soil moisture levels, although this assertion requires field testing.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Jorge Toledo, Trevor Williams, Jorge E. Ibarra

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
evaluation - screening - selection
environment/habitat manipulation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Anastrepha obliqua
Steinernema carpocapsae/Xenorhabdus nematophila (entomopathogen)	Anastrepha obliqua