Intra-guild interactions between the parasitoid Aphytis lingnanensis and the predator Chilocorus circumdatus: Implications for the biological control of armoured scales

• Chilocorus circumdatus functional response (type II) was not affected by Aphytis lingnanensis.
• C. circumdatus showed no preference between parasitised and unparasitised scales.
• A. lingnanensis showed a type II functional response to Aspidiotus nerii density.
• A. lingnanensis shifted functional response to type III when predator was present.
• Parasitism behavior was not influenced by the presence of the predator.

The parasitoid Aphytis lingnanensis and the predator Chilocorus circumdatus are released in different crops to control armoured scales. Both natural enemies compete, to some extent, for the same resource and therefore they can induce intraguild predation interactions (IGP). In the present work, the consequences of these interactions on the parasitism and predatory efficiency of these natural enemies were assessed under laboratory conditions by studying potential changes in their functional responses.A type II functional response to host/prey density was observed in A. lingnanensis and C. circumdatus when acting alone. The predatory efficiency of C. circumdatus was not affected by the presence of A. lingnanensis in the same arena. Conversely, the parasitism efficiency of A. lingnanensis was affected by the presence of the predator. Due to IGP at low host densities there was a shift from functional response type II to type III. No changes in the handling time when the predator was present suggested that parasitism behavior was not influenced by the presence of the predator. C. circumdatus did not discriminate between parasitised and unparasitised scales. A recommended strategy in biological control programs could be the use of one of the two natural enemies at low infestation levels and to reinforce these releases with the other one at high densities of the pest.

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