Entomopathogenic nematodes: Amending soils to increase biological control of insect pests We repeated experiments to test whether EPN community structure can be engineered by managing soil water potential (see June 2014 report for results). Mixtures of Sd, Sx, Hi, and Hz were maintained with weevil larvae in soil low and high water potential. EPNs that recycle in weevils were periodically added to fresh columns with weevil larvae for several ‘generations’ (21 days each). During the first three ‘generations,’ Sd gradually, but consistently increased its presence in the EPN population from 45% to 55% in the dry (6% moisture) soil and remained steady at 22-30% in the wetter (18% moisture) soil. Steinernema sp. (Sx) constituted between 27-41% of EPNs in dry soil and 55-63% in moist soil, whereas Hz represented between 6-23% of EPNs without an effect of soil moisture. It is interesting that Hi did not persist in any treatment, given that Hi is the dominant EPN species in all of the ecoregions where citrus is grown. We reported that Hi is little affected by Catenaria spp., a fungal predator of nematodes, whereas the fungus is lethal to most other EPN species in controlled studies. Similarly, during monthly sampling for two years in 4 citrus groves, detection of Catenaria sp. was found to be inversely related to Sd abundance and positively related to Hi abundance (unpublished). Results such as these suggest the need to increase the complexity of the biota in these experiments to include natural enemies of EPNs in order to recreate selection pressures in microcosms that produce EPN communities comparable to those in the field. A future microcosm experiment will test this hypothesis. We continued comparing the biology of two closely related native species, Steinernema diaprepesi (Sd) and Steinernema sp. (Sx), with respect to survival mechanisms. When subjected to a range of relative humidity (50%-100%), Sx did not survive RH ‘90% whereas, Sd persisted on filter paper disks at 90% and greater RH. Moreover, when the two species were maintained 48 h in aqueous solutions of 30% glycerol, both lost volume with the loss of water but, upon rehydration for 24 h, most Sd became motile whereas all Sx ruptured. Thus, Sd (an inhabitant of well drained, central ridge soils) has superior capacity for osmoregulation and desiccation survival compared to Sx (an inhabitant of poorly drained, flawoods soils). An inferior capacity for osmoregulation may also affect the spatial pattern of Sx which has not been detected in coastal orchards where hypertonic conditions tend to be greater than in the inland flatwoods orchards. Plant parasitic Nematodes: Characterizing a new nematode pest and the prevalence of resistance breaking populations of the citrus nematode. Treated plots two nematicide trials conducted in east coast grapefruit on swingle. We identified a second site on the central ridge with 18-month-old trees heavily infested by dagger nematode (Xiphinema vulgare). Installed irrigation lines adjacent to exiting lines to initiate nematicide trials (oxamyl and an experimental nematicide/fungicide) that will continue for three years.