|Ratcliffe, R. - ARS, RETIRED|
|Alldredge, J. - WSU DEPT OF STATISTICS|
|Hennings, C. - WHEAT FARMER|
Submitted to: Journal of Kansas Entomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2003
Publication Date: October 1, 2003
Citation: CLEMENT, S.L., ELBERSON, L.R., YOUNG, F.L., RATCLIFFE, R.H., ALLDREDGE, J.R., HENNINGS, C. CHANGING CROP ROTATION AND TILLAGE PRACTICES INCREASE HESSIAN FLY POPULATIONS IN WHEAT. JOURNAL OF KANSAS ENTOMOLOGICAL SOCIETY. 2003. Vol.76(4):567-577. Interpretive Summary: The economic viability of the soft white winter wheat - summer fallow rotation system in central Washington is challenged by wind and water erosion on fallow ground in the summer and wheat fields in the fall, by invasive annual grass weeds such as downy brome and jointed goatgrass, and by diseases such as take all. A transition from this system to a continuous no-tillage spring crop production system would provide sufficient residue to cover and protect the soil surface from wind and water erosion, and would reduce the severity of some grass weeds and diseases. Conservation tillage, however, may enhance the survival of Hessian fly and increase the potential for this pest to cause economic damage. This team research by USDA-ARS entomologists, an ARS agronomist, and a wheat producer studied the potential for increased problems with Hessian fly in different cereal production systems. This research is important because it showed, for the first time, that the Hessian fly exists in central Washington dryland wheat production areas and that this fly can become a problem in continuous production of no-tillage hard red spring wheat. More importantly, this research showed that wheat producers can avoid problems with Hessian fly in no-tillage spring wheat by using fly-resistant varieties developed by wheat breeders.
Technical Abstract: A three-year study in Washington state quantified Hessian fly populations in different cereal production systems using on-farm replicated plots. This study also quantified natural mortality of fly populations in the systems, identified hymenopterous parasitoids of the fly, and determined the biotype composition of the fly population at the research site. Continuous no-till hard red spring wheat (HRSW) led to higher Hessian fly infestations from one year to the next. By the third year of the study, tiller infestations in no-till HRSW and soft white spring wheat (SWSW) production systems had increased to levels above the economic injury level of 13-20% for spring infested tillers. The spring barley cultivar in this study was resistant to Hessian fly. Fly infestations were non-existent or low on soft white winter wheat in 1998 and 1999, but were high in spring 2000 (27.7% infested tillers). Mortality of Hessian fly eggs and larvae in HRSW and SWSW averaged 88.5 to 91.7% in 1999 and 77.7 to 87.9% in 2000, yet larval survival was sufficient to account for economic damage on spring wheats. Ten hymenopterous parasitoid adults (7 Homoporus destructor, 2 Eupelmus alynii, and one Pediobius epignous) emerged from field collected puparia in 1999. The biotype composition of the fly population was 58% GP, 17% E, 14% F, 10%G, and 1% N. The high percentage of GP indicates that the resistance gene H3 is effective against the population, but this gene's effectiveness will diminish over time as frequencies of biotypes E and G increase in populations.