Invasive Species Compendium

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Abstract Full Text

Different parasitization parameters of pupae of native (Coccinella septempunctata) and invasive (Harmonia axyridis) coccinellid species.

Abstract

We studied the parasitism of the pupae of two predatory coccinellid species of similar body size, i.e. native Coccinella septempunctata L. and invasive Harmonia axyridis (Pallas). The pupae were collected through the period of coccinellid eclosion and parasitoid emergence from a patch of nettles (n=660) and from a pea crop (n=1293) in Central Europe where both coccinellid species developed together. Three parasitoid species were recorded: Phalacrotophora fasciata (Fallen), Phalacrotophora berolinensis Schmitz and Oomyzus scaposus (Thomson). The first species was the dominant parasitoid of C. septempunctata and the only one recorded in H. axyridis pupae. Parasitism by Phalacrotophora spp. was higher on nettle patches, with 42% of C. septempunctata and 3% of H. axyridis parasitized, and lower in pea crops, where the percentage of parasitized pupae was 11% and 0.5%, respectively. At both sites, the proportion of H. axyridis in the total coccinellid population increased during the 13-16-day period of adult eclosion, but the proportion of parasitized individuals of particular coccinellid species giving rise to parasitoids remained similar during the entire period. In C. septempunctata, the mean number of Phalacrotophora puparia that originated from a coccinellid pupa was 7.2±0.30 (range 1-21) on nettle patches, which was significantly more than on pea crops (3.9±0.21 puparia, range 1-9). The mean mass of Phalacrotophora puparia decreased with increasing number per host pupa. The results confirmed a greater (10-20 times) rate of parasitism of native C. septempunctata than of invasive H. axyridis and also revealed large differences in the rate of parasitism between the sites.