Comparison of ecosystem services provided by natural enemies in aphid-susceptible and aphid-resistant soybeans (Glycine max)

The ecosystem services provided by natural enemies in soybean aphid (Aphis glycines) susceptible and resistant soybean (Glycine max) were studied in Michigan during the summer of 2010. We hypothesized that the lower population of aphids in resistant fields would lead to a corresponding reduction in the number and diversity of natural enemies in the same fields and therefore a reduction in the ecosystem services. Quarter acre blocks of SD01-76R (aphid susceptible), LD 16060 (single gene resistant) and Sparta (multiple gene resistant) soybean lines were planted. Within these blocks, sixteen “aphid islands” were planted. Each island consisted of a single susceptible (SD01-76R) plant infested with five aphids. Eight islands were caged to protect the aphids from predation while the remaining plants were left open. Aphid numbers on each of the islands were counted and after fourteen days the ecosystem services of predation was determined. The aphid and natural enemy population in the surrounding block was monitored weekly. Other indicators such as egg mass predation were used to detect any difference in predation and ecosystem services between the varieties. No significant differences were detected between the ecosystem services in resistant and susceptible fields.