First record of Intraguild predation between Harmonia axyridis and Eriopis connexa (Coleoptera: Coccinellidae), at different aphids prey levels in Argentina

MIRANDE LUCIANA; FRANCESENA NATALIA; GUY SMAGGHE; DESNEUX NICOLAS ; SCHNEIDER MARCELA

Ghent

Simposio; 64th International Symposium on Crop Protection; 2012

Harmonia axyridis Pallas is a species native of Pekín (China). It is a generalist predator of aphids and other soft-body pests. It has been introduced for biological control worldwide and it has been associated with declines in indigenous natural enemies, particularly ladybirds. These declines have been attributed to ccompetition for resources and Intraguild Predation (IGP) that occurs among two predator species that share common prey species and are capable of feeding on each other. Two important factors that determine the degree and severity of IGP among coccinellids are the body size and the availability of prey.Eriopis connexa is a native species and more abundant coccinellid of the Neotropical Region whereas H. axyridis, was introduced in Argentina in 1996 for the biological control of Myzus persicae. Since its introduction there is not any study yet that shown the effects of this invader species over natural enemies in agro-ecosystems mainly on other Coccinellidae species.The aim of this work was to evaluate the IGP between H. axyridis and E. connexa at different aphid prey levels under laboratory conditions.Larvae were placed into the vials treatment within 24 h of first instar eclosion and maintain using a 0.18-liter cage. The bioassays were carried out at 25±0.5°C temperature, 75±5% RH and 16:8 L:D of photoperiod.The treatments were displayed as follow: 1) two larvae per cage of each species (E. connexa and H. axyridis) supplied with low and high density of aphids per larva per day, respectively; 2) each species alone within the vials without competition, at low and high prey densities also. Each treatment was replicated 20 times. Larvae were fed daily according to the different density evaluated but within each density (low or high) the development stage was has into account to modified the amount of aphids at each larval instars. The survival, development time, weight of pupae and adult emergence was evaluated as endpoints.At the lowest prey level the developmental time of both species was slowest and the number of IGP was higher, acted H .axyridis, in the most cases as IG predator. H. axyridis pupae weighed more than pupae of E. connexa and this difference would determine the asymmetrical direction of the IGP, in which large individuals generally killed small ones.This work would confirm the negative effect of H. axyridis on a native coccinellid of the Neotropical region as E. connexa.