BIOTYPE STATUS OF HESSIAN FLY (DIPTERA, CECIDOMYIIDAE) POPULATIONS FROM THE EASTERN UNITED-STATES AND THEIR RESPONSE TO 14 HESSIAN FLY RESISTANCE GENES

Twenty-eight Hessian fly, Mayetiola destructor (Say), populations from 15 states in soft winter wheat area of the eastern United. States were evaluated for biotype composition and response to 14 Hessian fly resistance genes. The biotype composition of each Hessian fly population was estimated by confining individual gravid females on the wheat differentials 'Seneca' (H7H8), 'Monon' (H3), 'Abe' or 'Magnum' (H5), and 'Caldwell' (H6). The response of Hessian fly populations to resistance genes not deployed in the eastern United States was evaluated in replicated tests with wheat containing H9, H10, H12, H13, H14H15, H17, H18, and H19+ genes and two Purdue germplasm lines with unknown sources of resistance ('ACC 1566-1-1-IX' and 'Giorgio 331-39-10'). Based on biotype determinations, H7H8 was resistant or moderately resistant to populations from the South and Southeast, H3 and H5 were resistant to populations from East Texas, H6 was susceptible to all but the ML-TX population, and no deployed genes were resistant to populations from most locations in the Midwest and in the Mid-Atlantic region and the Northeast. Predominant biotypes in Florida, Georgia, and South Carolina were E, G, and 0, respectively. Biotype L was predominant in populations from the Midwest and some states of the Mid-Atlantic region. Texas populations were predominantly GP and A. The most resistant undeployed genes or gene combinations were H9, H13, H14H15, and H17, but Hessian fly virulence was found to all genes except H17. Continued monitoring of biotype frequency in Hessian fly populations is required for optimal deployment and management of resistance genes.