Feeding damage effects of three aphid species on wheat root growth

Cereal aphid infestations have considerable impact upon productivity and profitability of United States agriculture. A comparison study of the influence of different aphid species (Russian wheat aphid, Duraphis noxia Mordvilko; greenbug, Schizaphis graminum Rondani; and bird cherry oat aphid, Rhopalosiphum padi L.) upon shoot characteristics and root growth of hard red spring wheat (Triticum aestivum L.) was conducted in an attempt to better understand the mechanisms of yield loss in aphid damaged plants. Plants infested with aphids showed similar reductions in shoot growth regardless of aphid species. Shoot chlorophyll concentrations were lowest in greenbug‐infested plants. Root length and dry weight were also equally reduced by feeding damage by the three aphid species. Upon removal of the aphids, shoot dry weights of plants damaged by each aphid species remained unchanged for 10 days. Shoot dry weights for aphid‐damaged plants were about half the magnitude seen in 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 control plants. Within 10 days after aphid removal, however, chlorophyll concentrations across all treatments were essentially equal. Root lengths in plants previously infested with greenbugs or Russian wheat aphids were lower than control plants four days after aphid removal. Within 10 days after aphid removal, root lengths in plants previously infested with greenbugs or Russian wheat aphids did not differ from control plants. Root lengths in plants previously damaged by bird cherry oat aphids did not reach the same magnitude as that of the other treatments until 27 days after aphid removal. These results indicate that aphid feeding damage to wheat plants can have significant effects on root growth, suggesting that crop management practices that promote root growth could play important roles in improving plant tolerance to aphid damage.