By Adam Varenhorst and Philip Rozeboom et.al
Aphids are present in South Dakota wheat fields, and that means it’s time to start scouting. Currently, the aphid populations are still well below the threshold levels. The species observed include greenbug, bird cherry oat aphid, and English grain aphid. Aphid populations tend to increase unless there is an abundant natural enemy population present or if management occurs. At this time, fields should be scouted regularly to ensure that thresholds are not exceeded.
These will vary in color from olive to dark green and can be identified by the characteristic burnt red-orange patch that is present on the end of the abdomen near the cornicles or “tailpipes”. Bird cherry oat aphids can be difficult to scout for without a sweep net due to the defensive behavior of falling off the plant when disturbed. They will typically be present on the underside of the leaves, as well as the stem.
Most will be light to dark green in color, but it is possible to also observe a light-brown variation of English grain aphids. They can be identified by their black antennae, cornicles, and joints of each leg. English grain aphids are large in size. During heavy infestations, they can be present on almost every part of the plant aboveground.
These aphids are light green in color and can be identified by the dark-green stripe present on their back. Feeding by this species causes yellow discoloration and red spots on the leaves, due to a toxin present in its saliva.
Source : sdstate.edu