Progress 07/01/01 to 06/30/04
Outputs
Biological control of the soybean aphid was the principal subject of field research in 2003. Two lines of work were followed: Predator and entomopathogen. One important predator is a scymnine beetle that is specialized to attack ant-tended aphids and the soybean aphid is commonly defended by the cornfield ant. We investigated the role of ants in aphid populations in field cage studies. The presence of ants tripled aphid populations in the presence of most predators. The scymnine beetles reduced aphid numbers considerably, but aphid densities with ants were still 50 % higher in beetle cages than in cages without ants. The management of soybean aphids is likely to require ant management. Laboratory investigations of the entomopathogenic fungus, Neozygites fresnii, revealed that it is an important limiting factor for aphid densities. Unfortunately, though, the threshold density for the fungus appears to be about 250 aphids/leaflet which is too high to avoid economic
damage from the aphid. Economic optimization models of the HACCP protocol continue to progress. A model of the use of IPM as an implementation vehicle for HACCP protocols has been submitted for publication.
Impacts
In concert with the decision thresholds developed in the previous year, along with the product testing done in previous years, we now have management guidelines that are ready to be used.
Publications
- Brown, G. C., M. J. Sharkey, and D. W. Johnson. 2003. Bionomics of Scymnus (Pullus) louisianae J. Chapin(Coleoptera: Coccinellidae) as a Predator of the Soybean Aphid,Aphis glycines Matsumura (Homoptera: Aphididae). J. Econ. Entomol. 96:21 - 24.
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Progress 01/01/02 to 12/31/02
Outputs
Eighteen field releases of 250,000 aphids each (two sites, three growth stages, three planting dates) on three different varieties failed to generate substantial aphid populations in continuous soybeans but did generate aphid populations in soybeans following corn. The rotated soybeans were populated with cornfield ants, Lasius species, which tended the aphids and protected them from predation. These ants were not present in the continuous soybeans. The ants protect aphids from predation and enable the aphids to build to very high numbers. This factor will have to be included in any decision making rules. This may suggest a cultural control. The aphid predator, Scymnus louisianae, was again studied this past year. Video images indicate that it is specialized at preying on ant-tended aphids and that the waxy defenses prevent the ant from recognizing the predator larvae. These larvae and an unidentified syrphid (also unrecognized by the ants) were the only predators
found in ant-tended aphid colonies. However, the ants quickly dispatched those predators commonly found in the continuous soybeans (e.g. Harmonia axyridis, Chrysopa carnea) when these predators were artificially introduced. Bioassays of chemical insecticides showed that these aphids are highly susceptible to common soybean insecticides.
Impacts
This research will lead to methods of managing this new aphid pest in soybeans throughout the southeastern USA. It will also contribute to the management of other aphid species in areas where aphids are ant tended.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
Field evaluation of the economic impact of the aphid on soybeans of differing maturity groups and infestion times was conducted at two Kentucky locations. A HACCP plan for soybean aphid management was developed. Transmission of SMV by soybean aphid was confirmed. Bionomics of a coccinellid, Scymnus louisiane, was studied. Manuscript submitted in November.
Impacts
This work will lead to a soybean aphid management plan for maturity groups grown in the southern region.
Publications
- No publications reported this period
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