Yesterday I looked at three triticale fields that are also grown for seed to check aphid presence. We’ve been talking a lot about the Barley Yellow Dwarf Virus (BYD) – a virus of small grain vectored by aphids. According to UGA Extension Grain Entomologist Dr. David Buntin, planting date is the most most important management practice of BYD. Small grain fields planted early (October 1-15) are more susceptible to BYD than later planted fields. Of small grains, oats are most susceptible to BYD. If we’re growing for yield, seed, etc, we need to be aware of aphids.
Generally, now is the time to apply insecticide for a treatment of aphids. Nonetheless, we still want to check for aphids 25-30 days after planting.
There are about five species of aphids present in our fields: bird-cherry oat, rice root aphid, greenbugs, corn leaf aphid, and English grain aphid. The aphids I am seeing are bird-cherry oat aphid and green bugs. The bird-cherry oat aphids are the most common vector of BYD, even though any species can vector the disease. The green bug is the only species that can damage leaves. Although this is minimal damage, it shows up as small purple/red marks on the leaves (below).
In wheat, our threshold of aphids during tiller stage is 6 per row foot. You can use this same threshold for other small grains. However, many fields were broadcasted, so check square footage instead. In all fields I checked I saw adult aphids and young, which means they are reproducing. I could also see aphids while standing up (usually I have to get down on the ground and hunt them.) I was also seeing many fat, red-orange aphid. This is a mummy aphid that was parasitized by a wasp (below, left).