Assessing Impacts on Non-Target Aphids

Aphis monardae is an aphid species under study for potential non-target impacts. In prairie habitats, A. monardae populations aggregate in flower heads of their host plant, Monarda fistulosa

When introducing new natural enemies for long-term (permanent) biological control, it is essential to minimize potential unwanted affects. As part of the NCSRP Soybean Aphid Biological Control Project, we have been assessing the potential for negative impacts of those Asian natural enemies that we are considering for release to control the aphid.

As part of this effort we have worked to identify a group of native U.S. aphids for field sampling that complements laboratory host specificity testing and other studies. We followed a stepwise procedure to define a group of aphids for study. We first compiled a list of the 400 aphid species in Illinois, under the assumption that we would find many, if not most, throughout the Midwest. We then applied a set of three "filters" to pare the list to a manageable size.

Filter A – Aphid phylogeny. We have focused on aphids most closely related to the soybean aphid. Other aphids, more distantly related, are found in places we felt soybean aphid natural enemies would not be typically searching for hosts to attack. This left about 300 aphid species.

Filter B – Aphid origin. We decided to focus only on native aphids, as these species represent our natural U.S. fauna. This left about 200 species.

Filter C – Host plants. We then identified host plants that are shared between at least two aphid species. This was done to increase the chance that we would encounter aphids in our sampling.

By applying the filters, we arrived at 84 aphid species on 32 plant taxa. Most plants are found in prairies, grasslands or old fields. Others are wetland plants or are found in wooded areas.

We use transect sampling and visual observations to locate aphids, to measure their relative densities (and those of their host plants), and to collect to rear their parasitoids. We also use sweep-net sampling to collect predators and get a measure of other aphids in the habitat. We hope to describe the relative abundance and distribution of the aphids, and have an estimate of the “natural enemy load” the aphid species are carrying (e.g., relative parasitism rates and densities of predators).

We will use these data to assess the relative risks of non-target impacts, along with study in Asia, the suction trap network, previous aphid biocontrol programs, and host specificity testing. We will conduct a risk analysis to find a balance of benefits of controlling the soybean aphid and potential harm via non-target impacts on native aphid species.

Research Publications 2007

Heidel, T. H. and R. J. O’Neil. Survey of aphids of Indiana and their associated natural enemies as part of a study of nontarget effects of a classical biological control program of the soybean aphid. Presented at the annual meeting of the Entomological Society of America, December 2007. Read abstract»

Lagos, Doris and D. Voegtlin. A Survey of the Aphis spp. of the Midwestern States. Presented at the Annual Meeting of the Entomological Society of America, December 2006.

Wyckhuys, K. A. G., R. L. Koch, and G. E. Heimpel. 2007. Physical and ant-mediated refuges from parasitism: implications for non-target effects in biological control. Biological Control 40: 306-313. Read abstract»