Bracon nigricans was collected in Italy on the South American tomato pinworm, Tuta absoluta (Lepidoptera: Gelechiidae), an exotic pest of solanaceous crops. This wasp is one of the fourteen species collected during a two-year (2009-11) field survey. It was successfully reared for more than twenty generations with no apparent adverse effects on the parasitoid performances. We studied the biology and behaviour of the wasp under laboratory conditions and we documented its life tables. Bracon nigricans proved to be a gregarious, idiobiont, arrhenotokous ectoparasitoid of T.absoluta mature larvae. Adults fed on a sugary-proteinic nutritive food source lived longer and produced more progeny than those provided only T. absoluta host larvae. The parasitoid progeny was correlated to host densities, and the parasitism rate was higher at lower host densities. Because females should mate multiple times to be able to produce females through their life span, sex-ratio mostly depended of male longevity (i.e. availability of males). Both females and males were reproductively active soon after emergence. Parasitoid females showed intense stinging activity before effectively starting to lay eggs on hosts. During this pre-oviposition activity, parasitoid female may inject venom for paralyzing hosts and also may assess host suitability (based on host size and/or host haemolymphatic kairomone recognition) for immature parasitoid development. The proportion of hosts that were permanently parasitized was stable in all the trials. Although semi-field and field studies would be needed, this braconid parasitoid could be an effective biological control agent of T. absoluta on tomato in Europe.

Biology and behaviour of Bracon nigricans (szépligeti) (Hymenoptera: braconidae), an indigenous parasitoid of Tuta absoluta (meyrick) in Italy

BIONDI, ANTONIO;ZAPPALA', LUCIA
2011

Abstract

Bracon nigricans was collected in Italy on the South American tomato pinworm, Tuta absoluta (Lepidoptera: Gelechiidae), an exotic pest of solanaceous crops. This wasp is one of the fourteen species collected during a two-year (2009-11) field survey. It was successfully reared for more than twenty generations with no apparent adverse effects on the parasitoid performances. We studied the biology and behaviour of the wasp under laboratory conditions and we documented its life tables. Bracon nigricans proved to be a gregarious, idiobiont, arrhenotokous ectoparasitoid of T.absoluta mature larvae. Adults fed on a sugary-proteinic nutritive food source lived longer and produced more progeny than those provided only T. absoluta host larvae. The parasitoid progeny was correlated to host densities, and the parasitism rate was higher at lower host densities. Because females should mate multiple times to be able to produce females through their life span, sex-ratio mostly depended of male longevity (i.e. availability of males). Both females and males were reproductively active soon after emergence. Parasitoid females showed intense stinging activity before effectively starting to lay eggs on hosts. During this pre-oviposition activity, parasitoid female may inject venom for paralyzing hosts and also may assess host suitability (based on host size and/or host haemolymphatic kairomone recognition) for immature parasitoid development. The proportion of hosts that were permanently parasitized was stable in all the trials. Although semi-field and field studies would be needed, this braconid parasitoid could be an effective biological control agent of T. absoluta on tomato in Europe.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11769/248532
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