Ants (Hymenoptera: Formicidae) Associated with Diaphorina citri (Hemiptera: Liviidae) and their Role in its Biological Control

After the arrival of the Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae) in Florida, several studies mentioned the presence of ants where D. citri was present, but there was no clarification of their specific interaction with the psyllid. The goal of this study was to elucidate the role of ants in the biological control of D. citri by observing ant behavior and by determining if ant presence, modified by exclusion manipulations, affected parasitism of D. citri by Tamarixia radiata (Waterston, 1922) (Hymenoptera: Eulophidae), an introduced parasitoid of the psyllid, when the insect was infesting orange jasmine, Murraya paniculata (L.) Jack (Sapindales: Rutaceae) and Persian lime, Citrus latifolia Tanaka (Sapindales: Rutaceae). During a preliminary survey on M. paniculata in Homestead, Florida, we observed 2 ant species in association with D. citri, i.e., the big headed ant, Pheidole megacephala Fabricius, and the rover ant, Brachymyrmex obscurior Forel. In 2 ant exclusion experiments, using a 2-cm-wide barrier of Tanglefoot®, P. megacephala was the only ant species found in M. paniculata while P. megacephala, B. patagonicus and Solenopsis invicta Buren were observed in C. latifolia. The number of P. megacephala found in the unprotected flushes in M. paniculata fluctuated between 0.15 and 0.5 per flush while in C. latifolia the number of ants, pooled across species, varied between 1.44 and 6.61. In M. paniculata flushes from Tanglefoot-treated plants, 20.36% of the nymphs were parasitized by T. radiata compared to 0.39% parasitism in untreated control flushes where ants had not been excluded. Fifty-eight percent of the psyllid nymphs were parasitized in the C. latifolia Tanglefoot® ant-exclusion flushes compared with 8.57% parasitism in the non-exclusion control. An additional experiment using the ant bait Extinguish Plus® (Hydramethylnon 0.365%+ S-Methoprene 0.250%) applied to the soil surrounding the trunk showed that the use of a granular bait can help to reduce ant populations and consequently increase the percentage parasitism of the Asian citrus psyllid.