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Project 6

Project title: Integrating New Natural Enemies into Soybean Aphid Biological Control.
Investigators: Michael Brewer, Doug Landis, Alejandro Costamagna, Takuji Noma, Matthew Kaiser and Shaun Langley, Michigan State University, Integrated Pest Management Program, Department of Entomology, B18 Food Safety and Toxicology Building, East Lansing, MI
Contact: Michael Brewer (brewerm@msu.edu)

Project description: We conducted field studies to 1) assess extant parasitoid and predatory fly species that may be adapting to prey upon the invasive Aphis glycines, soybean aphid, and 2) examine the role of predators in limiting parasitoid impacts via intraguild predation.

For objective 1, we detected parasitoids and predatory flies attacking sentinel A. glycines on potted soybean plants. In 2004 and 2005, we detected five species of parasitoids and eleven species of predatory flies parasitizing sentinel A. glycines. Most common utilizing A. glycines were the parasitoids Aphelinus asychis, Lysiphlebus testaceipes, and a newly described species Binodoxys kelloggensis, and the flies Aphidoletes aphidimyza, Allograpta oblique, and Sphaerophoria contigua. Variation in habitat affinity was detected: L. testaceipes, A. oblique, and S. contigua utilized A. glycines placed in all crop and noncropped habitats; B. kelloggensis was principally found utilizing A. glycines placed in noncropped early successional vegetation and poplar stands; A. asychis most commonly utilized A. glycines placed in soybean; and A. aphidimyza was most common in soybean and other cropped plots. Percent field parasitism of A. glycines in soybean as measured by field inspection for mummies was disappointing, never exceeding 1%. Predatory flies were commonly found preying on A. glycines in soybean.

For objective 2, a field experiment examined the role of predators in limiting parasitoid impacts via intraguild predation (IGP). Using tomato cage frames covered with mesh we differentially excluded all natural enemies (< 1 mm mesh) or only large predators (2 mm mesh), thus allowing natural parasitism to occur protected from IGP by large predators. We also included un-caged plants with and without A. glycines manipulation, plants enclosed with a sham cage as a cage control, and plants caged without A. glycines. Our results showed strong impact from large predators (mainly Coccinellidae) but very low parasitism and predation achieved by extant parasitoid populations or small predators. Intraguid predation did not play a limiting role in parasitism.