Ants (Hymenoptera: Formicidae) Reduce The Density Of Cacopsylla Pyri (Linnaeus, 1761) In Mediterranean Pear Orchards

Ants have a strong impact on the population dynamics of sap-sucking hemipterans, but their role in pest control in pear orchards is still to be clarified. The pear psyllid, Cacopsylla pyri (LINNAEUS, 1761), is the main pest of pear trees in the Mediterranean area and temperate Europe. Integrated pest management and biological control are good alternatives for the control of psyllids. The aim of this work was to determine the effect of ants on the control of the psyllid. This was investigated in one pear orchard through an experiment involving a randomised block design with two factors: (1) ant exclusion with and without and (2) psyllid density three levels. The pear trees accessible to ants (namely Lasius grandis FOREL, 1909) had significantly lower psyllid abundances than those from which ants were excluded; the effect of ants was significant for the three density levels of the psyllid assayed. Ant abundance showed a non-linear relationship with honeydew; an increase in ant abundance until approximately 5% of the leaf surface was impregnated with honeydew, with a subsequent decrease at higher values, was predicted. The abundance of coccinellids and anthocorids was significantly lower in the presence of ants. Ants had a strong effect, lowering the numbers of psyllids. Overall, ants seem to contribute positively to biological pest control in pear orchards. The non-linear numerical response of ants may have important implications in the control of psyllids; the washing of excessive honeydew from trees is advised to improve the predatory response of ants.