The English grain aphid, Sitobion avenae, has been found in South Dakota in high numbers on wheat. This is a relatively large aphid, about 1/10 inch long, light green to brown with black antennae, and clearly visible black cornicles. It is a known vector of Barley Yellow Dwarf (BYD), but the major damage to wheat is caused by the aphid’s direct feeding injury to the heads of small grains. Foliage damage occurs until grain begins to head. Once heading initiates, these aphids move and aggregate at the heads and aggressively feed upon the ripening kernels.
Scouting should begin roughly 100 ft or 20 paces from the field edge. Individual stems and leaves should be inspected for aphids or signs of damage on 10 plants in five locations in the field. Field ants can be an indicator of an aphid threshold as they harvest the sugary secretion called honeydew that the aphids produce. The specific thresholds for English grain aphids are 30 per plant when wheat is in seedling stage, 50 when in boot to heading stage, 5 when wheat is flowering, and 10 or more during heading. Several insecticides with pre-harvest interval of 14-15 days are registered for aphid control, and as we are getting closer to harvest, the pre-harvest interval will be an important factor in selecting insecticides to apply against these pests. It is always advised to scout before applying pesticides, as insecticide applications before aphids reach threshold have severe negative effects on populations of beneficial insects that can successfully suppress low levels of aphids. For more information about aphids, access the related publication below.
Source : SDSU