Soybean Pests and their Management Practices

Which are the most important pests in soybean, and how to control them efficiently

To protect the yield potential of soybean plants, farmers must monitor their crops often and apply suitable preventive and management measures for soybean pathogens and pests when needed.

Below are some of the most important pest enemies of soybean and management practices.

1. Gram pod borer: Helicoverpa armigera

Helicoverpa can attack soybeans at any plant developmental stage, from seedling to pod ripening. However, they will most likely attack during the flowering, podding, and pod-fill stages.

helicoverpa armigera soybean

Identification – How to identify Gram pod borer and the infestation symptoms early

Please note that loopers and Helicoverpa differ in the number of pairs of ventral prolegs they possess. Loopers have 2-3 pairs of ventral prolegs, while Helicoverpa have 4 pairs.
Please be aware that there is a distinction between Helicoverpa and cluster caterpillars. Although both have 4 pairs of ventral prolegs, cluster caterpillars can be identified by their broader and smoother appearance, as well as the presence of 4 rows of distinctive black spots.

Symptoms of damage from Helicoverpa in soybean

By feeding on the young leaves, the larvae skeletonize them, decreasing the photosynthetic capability of the plants.
In the early stage, they feed voraciously on the foliage, may defoliate the plant, and later feed on flowers and pods.

Control measures – How to control Gram pod borer:

Apply deep summer plowing in the field.
Install pheromone traps for controlling this insect pest, at a distance of 50 m, with 5 traps per hectare.
Erect bird perches (50 per hectare)
On the 100th day of crop growth, perform the task of clipping terminal shoots.
Set up light traps with a ratio of 1 light trap per 5 acres to effectively kill the moth population.

2. Cutworms: Spodopteralitura fabricius

Cutworms are considered early-season insect pests that can affect pulse crops. Multiple species of cutworms can be found in these crops, and their lifecycles can vary. Cutworms may take anywhere from 65 to 87 days to complete all their larval stages, but it’s important to note that damage may not occur throughout this period.

Identification – How to recognize cutworms

The mature larvae of cutworms can reach lengths of up to 46 mm. They have a smooth texture, and their coloration ranges from purplish to brown. These larvae have grey lines and spots on their body.
The adult cutworms typically are 20 mm long. They have long, narrow, and usually dark in color forewings. Near the tips of the forewings, there is a pale area with three black dashes on each forewing. The wing span of adult cutworms can vary between 38 to 50 mm.

Symptoms of damage caused by cutworms in soybean

Severing young plants from roots near the soil line, the first generation of cutworm larvae is the most damaging. Some cutworms also feed on the roots and underground stems of cut plants. Until it pupates in the soil, one larva can kill many plants.
The foliage has signs of eating activity and is decreased.
Due to the absence of below-ground growing points, soybeans cannot regrow after being cut off by cutworms.

Control measures of cutworms in soybean:

To minimize the risk of cutworm infestations, it is recommended to control weeds in and around fields before planting soybean.
To prevent larvae from infesting crops, aim to control potential hosts at least 2 weeks before planting.
For optimal efficacy, it is advised to apply chemical control in the late afternoon or evening, when larvae typically emerge to feed at night, ensuring a higher probability of contact with or ingestion of the insecticide.
Using ground rig applications provides the flexibility to selectively treat affected areas or apply a border spray in situations where larvae are moving into the crop from adjacent weeds.

3. Soybean Aphids: Aphis glycines

Aphids are commonly found on the underside of the newest leaves in plants. If aphids are present on the stem or petioles, it is usually an indication of a high aphid population on the plant. This is because the stem and petioles are less preferred as a food source, and aphids typically migrate to these areas only when they become overcrowded.

Identification

The number of generations per season for aphids can vary depending on weather conditions, ranging from seven to 15 generations. In favorable weather conditions that support multiple generations, aphid populations can rapidly increase to levels where control measures are necessary. This rapid population growth is due to their ability to reproduce through cloning. Therefore, it is important to closely monitor aphid populations once identified to assess their growth and take appropriate action if necessary.
The soybean aphid is very small, 1.5 (mm) long, and light yellowed with distinct black cornicles.

Symptoms of aphids infestation

Soybean aphids extract plant juices, leading to decreased vigor, growth rates, leaf puckering, and reduced pod and seed counts. Ultimately, these factors may result in yield loss.
If the plant is subjected to additional stressors like drought, the damage caused by soybean aphids is intensified. Moreover, aphid honeydew, a waste product generated during feeding, encourages the growth of grey, sooty mold on leaf surfaces, thereby reducing the photosynthetic capacity of plants.
The soybean aphid serves as a vector for transmitting the soybean mosaic virus.

Control measures – How to control aphids:

Predators like green lacewings, snakeflies, and parasitoids, along with pathogenic fungi, can regulate population levels of soybean aphids when they are below 200-250 aphids per plant.
Once the economic threshold is reached, insecticides are available to safeguard crops. It is recommended to apply foliar treatments within 7-10 days of reaching the economic threshold.

4. Thistle Caterpillar: Vanessa cardui

Thistle caterpillars are occasional or sporadic pests in soybean fields.

Identification

The caterpillars of thistle caterpillars (demonstrated in the cover picture of the article) can grow to be two to three cm in length. They typically have a brown and black coloration with yellow stripes running down each side of their body. These caterpillars are covered in branched spiny hairs, which give them a bristly or prickly appearance.
After the caterpillar stage, they form a chrysalis that is goldish/brown. The chrysalis hangs from the plants as the transformation into a butterfly takes place. The adult butterfly, known as the painted lady butterfly, will eventually emerge from the chrysalis.
The pupa or chrysalis of thistle caterpillars is suspended from plants by silk threads.

Symptoms of thistle caterpillar infestation

Caterpillars are commonly found near their feeding sites, which occur inside a webbed area formed by the cupping of leaf margins.
Adults typically feed on the nectar of flowers, while the larvae gather and feed together within leaf nests formed near the tips of host plants.
Thistle caterpillars create webbing on the undersides of leaves, and they feed by puncturing cells to consume the cell contents. This feeding behavior leads to the leaves’ stippling, yellowing, or browning. The affected leaves may dry and drop prematurely in severe cases, reducing crop yields.
Infestations of thistle caterpillars typically begin at the edges of the field and progress inward. Extended periods of hot and dry conditions create favorable conditions for rapid population growth and exacerbate the feeding damage caused by thistle caterpillars.

Control measures:

When butterflies are highly abundant in a soybean crop, it is advisable to conduct weekly inspections of the crop until caterpillars are observed feeding on the plants.
To manage the population of thistle caterpillars, insecticide applications can be employed. However, consulting with your local representative or agricultural extension service is crucial to determine the most appropriate treatment plan for effectively managing thistle caterpillars.

5. Two-spotted Spider Mites: Tetranychus urticae

Two-spotted spider mites (Tetranychus urticae) belong to the mite family Tetranychidae. During winter, two-spotted spider mites can overwinter in various protected areas such as soil, plant debris, and grass, where they can survive until favorable conditions for their activity return.

Identification Two-Spotted Spider Mites

Two-spotted spider mites are very small, making them difficult to spot on plants without close inspection. Due to their tiny size, damage caused by their feeding activities is often noticed before the mites are observed. Monitoring plants for signs of damage, such as stippling or discoloration of leaves, can be an effective way to detect their presence.
Two-spotted spider mites are approximately 0.5 mm long and have eight legs. They have a greenish, yellowish, or orange oval-shaped body with two dark spots on their abdomen. These mites are visible to the unaided eye but appear as small specks due to their small size.

Spider mite adult and eggs (source Minessota University)

Symptoms of Two-Spotted Spider Mites

When two-spotted spider mites feed on soybean leaves, they suck contents out of leaf cells, causing injury. The undersides of leaves tend to have the highest concentration of white or yellow spots (stippling) resulting from the damaged plant cells caused by mite feeding.
Infested leaves, in severe infestations, will turn yellow to tan, or sometimes bronze-colored, and may drop off plants. Yield reduction can occur due to these infestations.
Mites disperse into fields from surrounding vegetation, and damage is often first noticed on field borders.

Control measures for Two-Spotted Spider Mites in soybean:

To identify mites, a helpful method is to shake leaves that exhibit symptoms over a white piece of paper. By doing so, you can observe if small dark specks are falling off the leaves, indicating the presence of mites. Additionally, it is essential to carefully examine the undersides of leaves for mite eggs. These eggs may be recognizable by the presence of minute webbing that covers them.
Implementing practices to minimize plant stress, such as improving irrigation, fertilization, and timely harvest, can be highly beneficial.
If mites are present in high numbers and the plants start to exhibit a bronzed appearance, it is advisable to consider spraying as a control measure. A second spray may be necessary after 7-10 days to target any newly hatched mites from previously laid eggs. In some cases, border or spot sprays may be sufficient. To prevent mite flare-ups, it is important to avoid using products that target other pests but also kill mites’ natural enemies.

6. White fly: Bemisia tabaci

There are multiple species of whiteflies, but the sweet potato whitefly (Bemisia tabaci) is the one most commonly associated with soybeans. Similar to soybean aphids, whiteflies secrete honeydew on the leaves and other plant parts, which can lead to the development of sooty mold, potentially inhibiting photosynthesis. Whiteflies are frequently found on velvetleaf or button weed, and soybean fields with dense weed populations may experience higher numbers of whiteflies.

How to identify whiteflies

Whiteflies are indeed sucking insects that feed on plant juices in both their immature and adult stages. The adult whiteflies are approximately 1/16 inch long and have four whitish wings. Their body is typically yellowish.
Whiteflies have wings that are held in a roof-like manner over their body, making them more or less parallel to the leaf surface. When walking through a field, whiteflies are easily disturbed and fly up into the air. The nymphs, the immature stages of whiteflies, feed on the undersides of leaves. They have a flattened appearance and resemble scale insects.

White flies in soybean (source soybean research info network)

Common Symptoms of Whiteflies

Due to the attack of the insect, the leaves turn yellow and become curled.
This insect spreads the mosaic disease (virus) in soybean.

Control measures:

For monitoring and captures of adult whiteflies, farmers can use yellow sticky traps.
The use of insecticides, like insecticidal soaps, or oils, such as neem oil, may reduce populations but not eliminate them.
Systemic insecticides may be more effective in controlling the disease.

Pavithra Sathnur

Agronomist

Verified

Experienced agricultural professional with expertise in tasks such as crop management and providing package of practices for various crops. provider of independent scientific research in crop protection, crop physiology, and soil management. Combine expertise in crop and soil science with digital technology to produce innovative services and products that improve business practices and help increase yields. This helps drive safe and secure food supplies and contributes to a sustainable and resilient industry. Experience of cloud data platforms enable real-time data capture and automatic crop management based on detailed research-based algorithms.

Join our editorial team

Join our community and contribute to Wikifarmer, a platform based on the knowledge of a diverse community of farmers and people working in the agricultural industry from all over the world.

Article submission