As small grains reach the flag leaf - boot - heading stages, we focus on cereal aphids and the plant diseases that could impact yield and quality. Field scouting activities this week did locate aphids, but the news isn’t all bad.

In general, populations were small, with infestations currently well below the treatment threshold of 80% infested stems. When aphids were found, the colonies were small with aphids numbering less than 10 per colony. Also, the prevailing species of aphid that was found was the English grain aphid. This aphid has been the dominant grain aphid in many past seasons. We typically see the populations build rapidly during the heading stages, with the aphids congregating on the grain heads. Fortunately, these rapid population increases are often short lived due to fungal parasites infecting and killing the aphids and rapidly increasing numbers of key insect predators such as lady beetles and syrphid fly larvae.

Another positive is that outbreaks of Barley Yellow Dwarf virus (BYDV), which is transmitted by cereal aphids, often are NOT associated with English grain aphid. BYDV outbreaks are more often linked to Bird-cherry oat aphids.

Aphids generally immigrate into this region around or slightly before tillering. The best time to scout for aphids is at or slightly before flag leaf. This provides enough time to assess aphid populations and determine if a treatment is warranted.