2010 Annual Report
1a.Objectives (from AD-416)
Improve integrated pest management (IPM) practices for cereal aphids in wheat, sorghum, and barley in the United States by developing knowledge and tools to enhance the role of host plant resistance and natural enemies in crop management strategies. This will involve: (1) developing fundamental knowledge of the biology and ecology of cereal aphids; (2) developing an understanding of how aphid biotypic variation is generated and maintained; (3) determining the population breeding structure of cereal aphids in North America and its relationship to evolutionary/genetic basis for aphid biotypes; and (4) developing principles, techniques, and decision support tools for managing cereal aphids and their natural enemies.
1b.Approach (from AD-416)
Field and laboratory experiments will be conducted to: (1) characterize the biotypic composition of greenbug populations occurring on non-cultivated hosts; (2) assess the role of grass species associated with cereal cropping systems in harboring pest aphids and their natural enemies; (3) monitor and characterize the biotypic structure of Russian wheat aphid populations on cultivated and non-cultivated hosts; (4) characterize holocyclic reproduction in the Russian wheat aphid and its role in biotype evolution; (5) determine the degree of genetic variation and the breeding structure of the Russian wheat aphid populations in the United States; (6) determine the genome size and organizational complexity of the Russian wheat aphid; (7) develop and test a natural enemy threshold for Coccinellidae against the greenbug in winter wheat; (8) develop airborne multi-spectral remote sensing techniques for monitoring greenbug infestations in wheat; and (9) develop computer programs to deliver pest management programs.
This is the final report for the project 6217-22000-013-00D, terminated in March 2010. There was a period between the beginning of FY2010 and the termination date for the project. All planned laboratory, greenhouse, and field experiments were completed prior to the start of FY2010; no experiments were initiated in the timeframe corresponding to this project.
Substantial results were realized over the 5 years of the project. New decision-making tools for controlling cereal aphids were developed through the elucidation of the relationships between the shape, size, and proximity of areas (patches) of stressed plants within wheat fields. These tools confer the ability to differentiate areas stressed by Russian wheat aphids from areas stressed by drought and cultural factors, and provide for the early detection of infestations using multi-spectral remote sensing technology. Molecular tools were developed that provide for the positive identification of all the major cereal aphid species. This DNA-barcoding system allows for the specific identification of these aphids at all life stages (eggs, nymphs, and alate and apterous adults). Eight new Russian wheat aphid biotypes were discovered in the U.S. and were phenotypically characterized, and their occurrence and distribution in the western U.S. documented. These new biotypes are now being used to identify new and more durable sources of Russian wheat aphid resistance for wheat and barley. Mitochondrial DNA analysis and cuticular hydrocarbon profiles confirmed that the U.S. Russian wheat aphid population is a result of a single introduction and the new virulent biotypes do not represent separate introductions. The occurrence of sexual reproduction by Russian wheat aphids was discovered and provided evidence that biotypes are being produced by genetic recombination during sexual reproduction. Ninety-three progeny that hatched from field-collected eggs revealed 48 unique biotypes. Sixteen new greenbug biotypes were discovered from wheat, sorghum, and wild grasses. Biotypic diversity and crop-virulence were greatest among greenbugs collected from grasses, confirming that wild grasses are fundamental to virulence development and maintenance.
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Randolph, T.L., Peairs, F., Weiland, A., Rudolph, J.B., Puterka, G.J. 2009. Plant responses to seven Russian wheat aphid (Hemiptera: Aphididae) biotypes found in the United States. Journal of Economic Entomology. 102(5):1954-1959.
Cooper, W.R., Dillwith, J.W., Puterka, G.J. 2010. Salivary proteins of Russian wheat aphid (Hempitera: Aphididae). Environmental Entomology. 39(1):223-231.
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