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Title: SEASONAL ABUDANCE OF RICE ROOT APHID IN WHEAT AND ITS EFFECTS ON FORAGE AND GRAIN YIELDS

Author
item Kindler, Dean - Dean
item Hesler, Louis
item Elliott, Norman - Norm
item ROYER, TOM - OKLAHOMA STATE UNIV
item GILES, KRIS - OKLAHOMA STATE UNIV

Submitted to: Southwest Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2004
Publication Date: 12/1/2004
Citation: Kindler, D., Hesler, L.S., Elliott, N.C., Royer, T.A., Giles, K.L. 2004. Seasonal abudance of rice root aphid in wheat and its effects on forage and grain yields. Southwestern Entomologist. 29(4):245-252.

Interpretive Summary: In recent years the rice root aphid has become abundant in winter wheat fields in Oklahoma. Little or nothing is known about its seasonal abundance or its effect on forage and grain yields of winter wheat. Therefore, field and laboratory studies were undertaken to determine its seasonal abundance in wheat in central Oklahoma and its effect on forage and grain yields. The field abundance of the rice root aphid. During the fall 2001 and 2002, the rice root aphid, corn leaf aphid, Bird cherry-oat aphid, and greenbug were found in winter wheat fields in Oklahoma. Rice root aphids infested winter wheat soon after emergence and continued to increase in number on the fall seeded crop until mid December when populations peaked and then began to decline. By early January the aphids were difficult to find. In a laboratory plant growth chamber study, rice root aphid populations of 3.6 aphids per tiller at the end of a 60-day infestation period significantly reduced the forage yield of wheat, which is significant since approximately 67% of the 6-7 million acres of winter wheat grown each year in Oklahoma is grazed by cattle. Grain yields from rice root infested wheat plants were lower than from non-infested plants but the difference was not statistically significant. Field studies showed that populations of rice root aphids of 3.6 per tiller or greater do occur in Oklahoma in fall of some years. All indications are that the rice root aphid is an important pest of wheat in Oklahoma, but more study is needed to accurately determine its economic importance.

Technical Abstract: Aphid seasonal abundance in wheat, Triticum aestivum L. was studied over a two-year period in Central Oklahoma with emphasis on the field abundance of the rice root aphid R. rufiabdominalis (Sasaki). The corn leaf aphid, Rhopalosiphum maidis (Fitch); oat bird-cherry aphid, R. padi (L.), rice root aphid, R. rufiabdominalis (Sasaki); and greenbug, Schizaphis graminum (Rondani), colonized winter wheat in Oklahoma during the autumns of 2000 and 2001. During each of the two years, rice root aphids infested winter wheat soon after emergence and continued to increase in number on the fall seeded crop until mid December when populations peaked and then began to decline, so that by early January the aphids were difficult to find. Rice root aphid populations of 3.6 aphids per tiller at the end of a 60-day infestation period significantly reduced the forage yield of wheat, which can be a significant economic impact since approximately 67% of the 6-7 million acres of winter wheat grown each year in Oklahoma is grazed by cattle. Grain yield was not significantly reduced by a 60-day rice root aphid infestation.