Aphids - General Considerations

In addition to aphids described in this guideline, there are several other species that may be found on beets 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 are constantly appearing 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. Frontal tubercles are small protuberances arising from the front of the head between and at the base of the antennae. They may be absent in some species. When present, they are usually rather prominent and may be convergent, pointing inward toward each other, or divergent, pointing outward away from each other. The cornicles are tubular structures that arise one each on the side of the body near the rear end. The cauda is a process resembling a tail and arises from the tip of the abdomen. Depending on species, it may be elongated, knobbed, triangular, or other shapes.

All aphids associated with sugarbeets are attacked by the same group of natural enemies. These include lady beetles such as the convergent lady beetle, Hippodamia convergens; the ninespotted lady beetle (normally not spotted in California), Coccinella novemnotata; and the sevenspotted lady beetle, C. septempunctata. Other important natural enemies are syrphid fly larvae, lacewing larvae, and parasitic wasps that cause aphids to develop into mummies (i.e., their bodies become dried and bloated and turn black or tan in color), and a fungus that attacks aphids but not plants, causing them to appear flattened or plastered to the leaf.

Aphid flights are most common during periods of moderate temperatures (60° to 80°F, 15° to 27°C). Monitor fields in the winter and spring from December through April. If aphids become numerous, increase frequency of sampling. Aphids are often concentrated in hot spots or near the field margin. Note the presence of any hot spots but avoid sampling only those areas. Also be sure to look for evidence of biological control; i.e., the presence of predators, parasites (aphid mummies), and disease.