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Abstract
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Tomato leaf miner (TLM), Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a serious pest of tomato pro-duction in many parts of the world. The TLM has demonstrated capacity to evolve resistance to insecticides, and
residues of these on tomato fruit pose hazards to human health, making biological control solutions an urgent
priority. We assessed the biological control potential of the predatory bug Nesidiocoris tenuis (Reuter), in com-bination with the egg parasitoidTrichogramma brassicaeBezdenko at various release rates (0, 10 or 30 females/
m
2
/week). Predators were released either 10 days before, or 10 days after, pest establishment. The predator
lowered pest density only when it was released before the pest, but not to levels likely to retain the population
below economic threshold. The parasitoid had no direct e ffect on pest density, but negatively a ffected the
predator's impact on the pest, likely by reducing prey suitability and shifting feeding behavior toward more
herbivory and/or cannibalism. Both pest and predator displayed negative density dependence; their population
growth rates declined with increasing conspecifi c density. Our results indicate that N. tenuis should be aug-mented using a predator-in-fi rst approach, and without simultaneous releases of egg parasitoids. Augmentation
of N. tenuis will require integration with other tactics to provide adequate control of TLM, but has the potential
for ancillary impacts on other tomato pests such as white flies and spider mites.
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