Examining vector movement among infected and noninfected hosts in the Rhopalosiphum padi-Barley yellow dwarf virus-wheat pathosystem

Barley yellow dwarf virus (BYDV) is transmitted by aphids and causes one of the most devastating diseases of cereals worldwide.  The bird-cherry oat aphid (BCOA), Rhopalosiphum padi (L.), is an important vector of BYDV-PAV.  Recent research showed nonviruliferous BCOA prefers BYDV-infected compared to noninfected wheat.  Understanding vector preferences and movement is important for disease management.  Our objective was to examine the movement of nonviruliferous aphids among BYDV-infected and noninfected wheat to understand the scale at which aphid vectors can distinguish between infected and noninfected hosts.  Assays were conducted in the laboratory using wheat.  In the first bioassay one leaf from a BYDV-infected and a noninfected plant was inserted into each end of a tube, overlapping in the middle.  Aphids were released on either the infected or noninfected leaf and their locations recorded 12 and 24 hours after release.  The second bioassay examined aphid movement along an array of five healthy wheat plants flanked on each end with noninfected or infected plants.  Aphids were released on the center plant and their locations recorded 19, 24, 43, 48 and 67 hrs after release.  Results of the first bioassay showed that aphids could distinguish between infected and noninfected leaves, preferentially settling on BYDV-infected plants 24 hrs after release.  In the second bioassay aphids showed no preference in the direction of their movement towards infected or noninfected hosts.  These results suggest that vector preferences observed in the laboratory are dependent on spatial scale. Studies are needed to better understand vector movement under field conditions.