Extraction of Diabrotica eggs from soil and determining whether Diabrotica oviposit in fields of oil seed squash

A soil washing apparatus was constructed and tested in collaboration with colleagues from the grant authority and project partners in Austria and Romania. It is based on a similar apparatus used in the USA but our apparatus can quickly process a large number of samples. The eggs were extracted by sieving and then floating on MgSO4-solution followed by sedimentation in water. Eggs of D. virgifera virgifera were separated from those of other species by studying the structure of egg surface. The efficiency of extraction of the apparatus was checked using samples spiked with blue coloured eggs. In co-operation with Austrian and Romanian colleagues a method was developed for sampling in the field. Eggs of D. virgifera virgifera were extracted from soil samples collected from fields in Austria and Romania in spring/summer and autumn 2011. The beetles did not appear to prefer to lay eggs at either the edges or centres of fields. As very few eggs were found at the edges of oil seed squash fields this crop does not appear to be a suitable habitat for egg laying.