Conservational biological control of the rosy apple aphid Dysaphis plantaginea (Hemiptera: Aphididae) in French cider apple orchards
Abstract: The rosy apple aphid Dysaphis plantaginea (Passerini, 1860) is a major insect pest in apple orchards in Europe, causing significant economic losses by reducing yield. Cider apple production, for which the perfect visual aspect of fruits is not an imperative for their marketability, offers good opportunities to study production systems favouring the biological control of pests and the reduction of insecticide use. To design new strategies to improve aphid biological control efficiency, a good knowledge of the dynamics of the pest and its natural enemies and on their interactions is required. The “Institut Français des Productions Cidricoles” carried out a study on the biological control of D. plantaginea in five insecticide free apple cider orchards from north-western France during two years (2014 and 2015). On each tree of these orchards, the aphid abundance, the natural enemy abundance by taxon, and the abundance of ants were counted in aphid colonies during the period of the rosy apple aphid presence (from the end of April to the beginning of July). Then the dynamics of the rosy apple aphid were divided in four periods: 1. colony establishment, 2. population increase, 3. peak abundance, and 4. population decrease. For each period, the population growth rates and the abundances of aphids, ants and each taxon of natural enemies were calculated. Principal component analyses were used to visualize the relationships between abundances and population growth rates. During the first and the second periods, the growth rate of D. plantaginea decreased with the increase in the natural enemy abundance, suggesting a significant biological control of this aphid during these periods. More specifically, biological control seemed to be mainly performed by hoverfly larvae and ladybirds.