Bulletin of Insectology (2005) 58, 135-140

Giovanni Burgio, Fabrizio Santi and Stefano Maini (2005)
Intra-guild predation and cannibalism between Harmonia axyridis and Adalia bipunctata adults and larvae: laboratory experiments
Bulletin of Insectology 58 (2), 135-140
Abstract: Direct interaction between adults and larvae of the ladybird Harmonia axyridis (Pallas) (exotic) and Adalia bipunctata (L.) (native) Coleoptera Coccinellidae, species was studied in the laboratory. Cannibalism (CANN) and intra-guild predation (IGP) were evaluated using simple bioassays to predict possible impact of exotic on native Coccinellidae. Bioassays were conducted using fourth instar larvae and adult female ladybirds that were individually confined in Petri dishes at 25 °C with 10 second instar larvae of the selected target species. The experiments included three treatments: i) only 10 coccinellid larvae, ii) 10 coccinellid larvae and 5 aphids and iii) 10 coccinellid larvae and 40 aphids. The aphid species used as prey was Myzus persicae (Sulzer). No significant differences between IGP and CANN of H. axyridis were detected, both for adults and fourth instar larvae. CANN of A. bipunctata was always significantly higher in comparison with IGP. In particular for the larvae and adults of A. bipunctata the consumption of interspecific larvae was very low. In some cases the females did not even show any predation of H. axyridis larvae. IGP of H. axyridis was always higher than CANN of A. bipunctata. H. axyridis showed a negative impact on A. bipunctata by direct means such as IGP, contrary to the findings of our previous experiments performed using eggs as the target. For H. axyridis in all bioassays on CANN and IGP against larvae, an inverse correlation was detected between the number of larvae consumed vs aphid density. For A. bipunctata an inverse correlation was detected only in the case of adult CANN. An asymmetric IGP between the two ladybird species, with a potential advantage for the exotic H. axyridis was shown. A preliminary risk assessment using these simple bioassays, rather than more complicated experiments, should always be performed before the introduction of a generalists predator as a biocontrol agent in a new agroecosystem.
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Database assignments for author(s): Giovanni Burgio, Stefano Maini, Fabrizio Santi

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

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Myzus persicae
Adalia bipunctata (predator)	Myzus persicae
Harmonia axyridis (predator)	Myzus persicae