The spatial distribution of a root fly in a barrier protected crop

Abstract: We report initial findings of an investigation into the effectiveness of a fence barrier inreducing ingress of Delia radicum flies into a field of rutabaga, and subsequent patterns ofoviposition and plant damage. We observed a 98% reduction in the number of flies caught onyellow sticky traps within the fenced crop compared with outside the fence. There was also achange in the sex ratios of catches with a reduction in the proportion of males recovered insidethe field. Data analyses of trap counts within and outside the fenced area using GLM methodsshowed that for both sets of data there were significant differences in catch between samplingdates, trap locations and also the two sides of the traps. Spatial patterns of trap catches showedthat female D. radicum were largely restricted to areas adjacent to the fence. Similar patternswere discerned for oviposition and damage to plants.