Population density of the rose-grain aphid,Metopolophium dirhodum, on four cereal species in Canterbury

Similar numbers of adult winged rosegrain aphid (RGA), Metopolophium dirhodum (Walk.), per unit area were recorded as immigrants on autumn-sown wheat, oats, barley, and rye in May-June 1987 at Lincoln.RGA population growth occurred at a similar rate up to the three-node stage of plant growth on these four cereals, and on wheat and barley blocks monitored in 1985. Subsequently, RGA numbers declined on wheat in 1985, and on wheat and rye in 1987, but population growth continued to a peak at heading or booting stages on barley and oats. Similarly, in a 1984 cultivar trial, scores for RGA infestation were consistently greater on barley and oat cultivars, than on wheat, triticale and rye, during the booting to flowering period of plant growth. The expression of resistance to RGA in older wheat and rye was thought to be partly associated with the rate of leaf senescence which reduced the area of feeding sites on sheltered lower leaves.