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Table 1 Comparison of index of aggregation (Ia) (the observed value of distance to regularity/the mean randomized value (Perry 1995)) values of four different studies on entomopathogenic nematode distributions using different approaches in various regions

From: Towards optimization of entomopathogenic nematodes for more service in the biological control of insect pests

EPN studied population Form of measured EPNs Ia value Comments (location) Reference
Heterorhabditis bacteriophora-infective stage juveniles (IJs) applied uniformly, in one or nine patches on Kentucky bluegrass EPN-infected Galleria mellonella larvae over time All mean values were less than one but differed (P ≤ 0.05) until 20 weeks, no more, after EPN application The values suggest a more even distribution than a random one (New Jersey/USA) Wilson et al. 2003
Natural populations of Steinernema feltiae and S. affine in grassland plots IJs assigned to one of 4 groups of increasing physiological age The values ranged 1.27–1.45 with group II as the most aggregated one All values indicate aggregated distribution (Merelbeke/Belgium) Spiridonov et al. 2007
H. bacteriophora- or S. carpocapsae-infected G. mellonella larvae applied within 24 h of initial IJ emergence to cultivated fields and adjoining grassy border plots H. bacteriophora and S. carpocapsae-IJs recovered from G. mellonella larvae baits applied several times after the cadavers Range < 1 to >2. Mean values differed between EPN species in bait traps and between soil management regimes at 48 h and 16 days after placing the cadavers, respectively Spatial distributions after dispersing from a grassy border into the adjacent cultivated field plots were more aggregated for H. bacteriophora than for S. carpocapsae (Ohio/USA) Bal et al. 2017
Natural populations of H. indica in citrus and mango grove EPN-infected G. mellonella larvae 0.913 Ia refers to even distribution (Giza/Egypt) Abd-Elgawad (unpublished)