Abundance and population dynamics of Cacopsylla pyri (Hemiptera: Psyllidae) and its potential natural enemies in pear orchards in southern Spain

Abstract

The abundance and population dynamics of the pear psyllid Cacopsylla pyri L. and its potential natural enemies were followed in pear orchards in southern Spain. The fieldwork was carried out from 2007 to 2010 in two chemically-treated and two non-treated orchards. The abundance of C. pyri gradually decreased through the years in both treated and non-treated orchards, but it reached lower levels in the former than in the latter. In the fourth year of the study the abundance of C. pyri was low in both orchards and the incidence of russet acceptable. Ants, spiders and the mirid Pilophorus gallicus Remane were the most abundant potential natural enemies interacting with C. pyri. The population of these predators progressively increased through the years in treated and non-treated orchards, although, the abundance of natural enemies was higher in the latter. P. gallicus reached high numbers at the same time as C. pyri and was probably responsible for controlling the psyllid outbreak in spring. Ants were abundant and may prey on C. pyri but also protect pear psyllid nymphs in exchange for honeydew. The increase in the number of spiders in summer was associated with a decrease in the number of ants and P. gallicus. Spiders could keep C. pyri at low levels during summer and autumn, which might reduce the number of overwintering adults and subsequent population growth in spring. The overall parasitism rates of C. pyri nymphs were low; Trechnites insidiosus (Crawford) was the only species of parasitoid found, together with the hyperparasitoid Aphidencyrtus mamitus Walker.