Soybeans: Soybean Aphid

Excerpt from 2002 edition of Agronomy Guide for Field Crops (Chapter 4)

Order 2009 edition of OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Description
2. Life History
3. Damage
4. Action Threshold
5. Management Strategies
6. Updates on Soybeans: Soybean Aphids
7. Related links...

Description

The soybean aphid is a small (pinhead-size), pale yellow aphid with black cornicles ("tailpipes") and a pale yellow tail. Adults may be winged or wingless. Nymphs are smaller than the adults and are wingless.

Plate 57. Soybean aphids are small and pale green and may be winged or wingless. Can be found on the underside of leaves and stems.

Life History

The soybean aphid, a pest originally from Asia, was first discovered in North America in 2000 and in Ontario in 2001. This insect has two primary hosts that it requires to complete its life cycle. The soybean aphid survives overwinter as eggs on the twigs of buckthorn species. In the spring, nymphs hatch from these eggs, and the aphids undergo two generations as wingless females on the buckthorn. The third generation develops into winged adults that migrate to soybean plants. The aphids then continue to produce wingless generations until the soybean plants become crowded with aphids and the plants experience a reduction in quality. Once crowded, winged forms are produced to disperse to more-crowded soybean plants. There can be as many as 18 generations of aphids per year. Like most aphids, the soybean aphids are all female, born pregnant and give birth to live nymphs. Males are only born in the fall so that the females and males can mate to produce the overwintering egg.

Damage

Aphids feed by piercing the plant tissue using a tube-like mouthpart and sucking the plant sap. Leaves on moderately to heavily infested plants will begin to pucker, curl and deform. Plants may become stunted. A reduction in pod and seed production may occur if aphid populations become extremely high. Aphid damage is more likely to cause yield reduction if the plants are already suffering from drought conditions or another stress factor. Aphids also excrete a sticky substance called honeydew, which can act as a substrate for grey sooty mould development. This insect may also vector soybean mosaic virus see the section Soybean Mosaic Virus. High-risk factors include fields under stress, which cause the plants to be less tolerant to the feeding damage.

Action Threshold

Thresholds are not available at this time.

Management Strategies

There are several natural enemies, including the ladybird beetle (ladybug), pirate bug and syrphid fly larva that are helpful in controlling this pest. A pathogen can also infect the aphids but requires warm, moist conditions to become established. Refer to OMAFRA Publication 812, Field Crop Protection Guide, for recommended products. Insecticide is only warranted in extreme cases, as the insecticide will kill the natural enemies and can cause a rebound in the aphid populations. (Order Publication 812)

Plate 58. Ladybird beetle larvae are a natural enemy of the soybean aphid.

Updates on Soybeans: Soybean Aphid

• Soybean Aphid
• Field Crop Protection Guide - Publication 812
  • Soybean Aphid

Related links...

• Insects
• Soybeans