Attraction and retention of Episyrphus balteatus DeGeer (Diptera: Syrphidae) at an arable field margin with rich and poor floral resources

Abstract

The abundance of a beneficial syrphid species along two strips of an arable field margin with contrasting floral richness were assessed to determine how the strips attracted and retained Episyrphus balteatus, whose larvae are aphidophagous. One margin strip was supplemented by eight species of flowering plants, planted between the hedgerow and the arable crop. E. balteatus was observed foraging on all eight species at this florally rich strip. A control strip had no additional floral resources other than those naturally present. E. balteatus was significantly more abundant at the rich strip over 21 trapping days. The effectiveness of each strip to retain. E. balteatus was assessed by observing and recording the time spent by paint marked individuals within each strip. The rate of dispersal of E. balteatus from each strip was determined from the percentage of marked individuals remaining in a strip over time. Data from trapping E. balteatus, and from determining their dispersal rates from the strips were used in a simple mathematical expression to show that E. balteatus were attracted into the rich strip more than the control strip on nine study days during the first half of the investigation. E. balteatus dispersed significantly more slowly from the rich strip on nine study days during the second half of the study. Managing hedgerows and fieldmargins to create florally rich habitats to attract and retain E. balteatus is an option farmers can consider if E. balteatus is to be encouraged into fields as part of a system of integrated pest management.