Aphids — General Considerations

Key to identifying aphids

In addition to aphids described in this guideline, there are several other species that may be found on cereals throughout the year. Many occur in extremely low numbers and cause no damage. If, however, you encounter large numbers of an aphid or aphids that do not fit any of the following descriptions, please contact your farm advisor or county agricultural commissioner immediately. New species occur frequently, and your assistance in finding these is greatly appreciated.

The antennae are appendages arising one each from the side of the head and function as sense organs. The cornicles are tubular structures that arise one each on the side of the body near the rear end. The cauda is a structure resembling a tail that arises from the tip of the abdomen. Depending on species, it may be elongated, knobbed, triangular, or other shapes.

All aphids associated with small grains are attacked by the same group of natural enemies. Historically these natural enemies and the advent of warm temperatures during spring keep aphid populations from reaching damaging levels. Natural enemies include lady beetles, syrphid fly larvae, green lacewings, parasitic wasps that cause the aphids to develop into mummies (i.e., their bodies become dried and bloated and turn tan or black in color) and a fungus disease that attacks aphids, but not the plants, causing them to appear flattened and plastered to the leaf or stem.

Check fields periodically after seedling emergence. If aphids become numerous, increase frequency of sampling. Before tillering, sample whole plants. After tillering, sample individual tillers. Aphids are often concentrated in spots or near the field margin. Note the presence of such hot spots but avoid sampling only these areas. Also be sure to look for evidence of biological control, presence of predators, disease, and aphid mummies.