Intraguild interactions between two biological control agents in citrus fruit: implications for biological control of medfly

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Abstract
The parasitoid waspSpalangia cameroniand the predatory beetlePseudoophonus rufipeshave long been studied for use as biological control agents against the Mediterranean fruit flyCeratitis capitata,particularly in citrus fruit orchards. Nevertheless, these two species of natural enemies, when competing for a common resource, may experience intraguild predation (IGP) interactions. These possible interactions, affecting parasitism and predation, have been evaluated in the present work, under laboratory conditions, through potential changes in functional response. Regarding host/prey density, both natural enemies, when acting alone, showed a type II functional response. Nevertheless, due to IGP,S. cameroni, in the presence ofP. rufipes, showed a higher fertility rate and a type III functional response. The parasitism behaviour ofS. cameroniwas affected by the presence of the predator, reducing the host handling time. Conversely, the parasitism rate ofS. cameronidid not vary in the presence ofP. rufipesbut the degree of superparasitism decreased and led to an increased fertility rate and an increasingly female‐biased sex ratio. Meanwhile, the predatory efficiency ofP. rufipeswas not affected by the presence ofS. cameronibut discrimination between parasitised and unparasitised pupae ofC. capitata, with a preference for the latter, was reported for this predator species. Our results suggest that in biological control programmes, the use of only one of these species is recommended at low infestation levels, whilst at high densities of the pest, the combination of both natural enemies seems to be the most appropriate strategy.
Funding Information
  • Programa Nacional Español de Becas de Formación de Profesorado Universitario (AP2010-2340)
  • Consellería de Agricultura, Medio Ambiente, Cambio Climático y Desarrollo Rural
  • Spanish Ministerio de Economia y Competitividad (CGL2010-16730, AGL2010-21349-C02-02)

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