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Title: IMPACT OF INDIGENOUS COCCINELLIDS ON RUSSIAN WHEAT APHIDS AND GREENBUGS(HOMOPTERA: APHIDIDAE) INFESTING WINTER WHEAT IN THE TEXAS PANHANDLE

Author
item MICHELS, GERALD - TEXAS AGRIC EXP STN
item Elliott, Norman - Norm
item ROMERO, R - DEPARTMENT OF THE ARMY
item FRITTS, D - TEXAS AGRIC EXP STN
item BIBLE, J - TEXAS AGRIC EXP STN

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2001
Publication Date: 6/1/2001
Citation: MICHELS, G.J., ELLIOTT, N.C., ROMERO, R.A., FRITTS, D.A., BIBLE, J.B. IMPACT OF INDIGENOUS COCCINELLIDS ON RUSSIAN WHEAT APHIDS AND GREENBUGS (HOMOPTERA: APHIDIDAE) INFESTING WINTER WHEAT IN THE TEXAS PANHANDLE. SOUTHWESTERN ENTOMOLOGIST. 2001. V. 26(2). P. 97-114.

Interpretive Summary: Experiments were conducted in Texas Panhandle winter wheat fields from 1993 to 1995 to determine the effect of natural enemies on Russian wheat aphids and greenbugs. The experiments demonstrated that naturally occurring predaceous coccinellids significantly reduced Russian wheat aphid and greenbug densities in irrigated and dryland winter wheat on a regular basis in the Texas Panhandle. The coccinellids were able to locate and attack isolated aphid infestations even when overall aphid density in the field was very low. Although the impact on aphid density varied from season to season, and year to year, the percentage reduction in aphid density was high, and relatively constant. There was no evidence that naturally occurring or established exotic parasitoids had a similar impact. This study adds to a body of evidence now accumulating regarding the role of natural enemies in aphid biological control in wheat and other field crops. The evidence indicates that these natural enemies can singly, or in combination with other natural enemies, stop aphid outbreaks from occurring. Future research should focus on further elucidating the role of naturally occurring enemies and ways to increase their effectiveness.

Technical Abstract: Exclusion experiments conducted in Texas Panhandle winter wheat fields from 1993 to 1995 demonstrated that naturally occurring predaceous Coccinellids (primarily Hippodamia sp.) had a significant impact on Russian wheat aphid, Diuraphis noxia (Kurdjumov), and greenbug, Schizaphis graminum (Rondani), average aphid density and percentage aphid reduction in both irrigated and dryland habitats. Naturally occurring predaceous coccinellids significantly reduced Russian wheat aphid and greenbug densities in irrigated and dryland winter wheat on a regular basis in the Texas Panhandle. The coccinellids were able to locate and attack isolated aphid infestations even when overall aphid density in the field was very low. Although the impact on actual aphid density varied from season to season, and year to year, the percentage reduction in aphid density was relatively constant, averaging 54% for Russian wheat aphids and 63% for greenbugs across all years and seasons. There was no evidence that naturally occurring or established exotic parasitoids had a similar impact.