FEEDING DAMAGE EFFECTS OF 3 APHID SPECIES ON WHEAT ROOT-GROWTH

Cereal aphid infestations have considerable impact upon productivity a nd profitability of United States agriculture. A comparison study of t he influence of different aphid species (Russian wheat aphid, Duraphis noxia Mordvilko: greenbug, Schizaphis graminum Rondani; and bird cher ry oat aphid, Rhopalosiphum padi L.) upon shoot characteristics and ro ot growth of hard red spring wheat (Triticum aestivum L.) was conducte d in an attempt to better understand the mechanisms of yield loss in a phid damaged plants. Plants infested with aphids showed similar reduct ions in shoot growth regardless of aphid species. Shoot chlorophyll co ncentrations were lowest in greenbug-infested plants. Root length and dry weight were also equally reduced by feeding damage by the three ap hid species. Upon removal of the aphids, shoot dry weights of plants d amaged by each aphid species remained unchanged for 10 days. Shoot dry weights for aphid-damaged plants were about half the magnitude Been i n the control plants after 15 days. Chlorophyll concentrations seen in greenbug and Russian wheat aphid-infested plants initially were lower than the concentrations seen in bird cherry oat aphid-infested and co ntrol plants. Within 10 days after aphid removal, however, chlorophyll concentrations across all treatments were essentially equal, Root len gths in plants previously infested with greenbugs or Russian wheat aph ids were lower than control plants four days after aphid removal. With in 10 days after aphid removal, root lengths in plants previously infe sted with greenbugs or Russian wheat aphids did not differ from contro l plants. Root lengths in plants previously damaged by bird cherry oat aphids did not reach the same magnitude as that of the other treatmen ts until 27 days after aphid removal. These results indicate that aphi d feeding damage to wheat plants can have significant effects on root growth, suggesting that crop management practices that promote root gr owth could play important roles in improving plant tolerance to aphid damage.