SummaryDuring the years 1989–1992 cereal aphids were caught alive in a low level (1.5 m high) suction trap operated in Le Rheu (Brittany, France) and tested for BYDV transmission. In most cases comparisons with data collected simultaneously by a 12.2 m suction trap operating in the same site resulted in good relationships between weekly catches at both heights.Results from transmission tests showed that: (i) the two main BYDV vectors wereRhopalosiphum padiandMetopolophium dirhodumduring the years of experiment; (ii) PAV and MAV were the commonest viruses and RPV was relatively scarce; (iii) during springM. dirhodumappeared to be the most important MAV vector and nearly as good a PAV vector asR. padi; (iv) during autumnR. padiwas the only vector of the three viruses with mixed transmission allowing it to transmit also MAV probably by heteroencapsidation. To give an indication of the risk of infection, infectivity indices were calculated by multiplying the numbers of aphids caught by the 12.2 m suction trap by the proportion that were infective. These infectivity indices agreed with field records of primary infection