An emerging organic citrus industry in Florida could benefit greatly from effective, non-conventional methods to mitigate losses from pests and diseases. We studied part of a soil food web in an organic orchard to
learn ways to conserve and enhance biological control of insect pests by native entomopathogenic nematodes (EPNs). We evaluated two OMRI (Organic Materials Review Institute) approved cultural practices: (i)
a mulch of commercially pelleted chicken manure, (ii) a commercial formulation ofPurpureocillium lilacinus, and (iii) an un-amended control. Several soil nutrients (i.e. nitrogen, phosphate, and potassium) were
affected by the amendments, but initial equilibrium values (T0) were restored by the last sampling time
(T12). The plant parasitic nematodeTylenchulus semipenetransincreased in both treatments compared to
the untreated control at T3 (P< 0.05). The oomycetePhytophthora nicotianaeincreased in the P. lilacinus
plots at T1, marginally at T12, but decreased at T6 and T9.Steinernema diaprepesi, Heterorhabditis indica
andHeterorhabditis zealandicawere the only EPNs regularly detected in the orchard. Mulch increased numbers ofH. zealandicaat T6 and T9 (P< 0.05) and free living nematodes at T12 (P< 0.01). The nematophagous
fungus (NF)P. lilacinuspersisted in plots where it was augmented (P< 0.05), reaching a maximum level at
T3 that was 17.5-fold greater than that in controls. Numbers ofPaenibacillussp. were directly related to
both those ofS. diaprepesiandAcrobeloides-group nematodes (P< 0.01), but inversely to the FLN counts
(P< 0.05). The application of these two amendments did not produce strong changes in the EPN community
but decreased the emergence from soil of adultDiaprepes abbreviatus, a root weevil pest. Thus, both amendments might contribute to citrus pest management under organic production