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Soybean: Common Diseases & Insect, Pests and Its Management

Soybean is an annual plant that grows for only one season and can reach heights of 0.2–1.5 m. Soybean, also known as Soyabean or soya, is a plant native to Northeast China.

Shruti Kandwal
Bacterial Blight
Bacterial Blight

Soybean is the most widely produced and consumed oilseed in the world. Soybean plants are typically erect shrubs with woody stems and alternately arranged leaves. The leaves have three individual leaflets that are oval or lance-like in shape and can grow to be 3–10 cm long. The soybean plant has small white or purple flowers and curved seed pods that are 3–15 cm long and can contain 1–5 seeds.

The seeds can be yellow, green, brown, black, or a mottled combination of these colors. Soybean is an annual plant that grows for only one season and can reach heights of 0.2–1.5 m. Soybean, also known as Soyabean or soya, is a plant native to Northeast China.

Some Common Soybean Plant Pests










A newly hatched fall armyworm caterpillar has a light body and a black head. The color of the body darkens with age. A prominent white inverted Y-shape on the head distinguishes fall armyworm caterpillars. In addition, four dark spots on the upper side of the caterpillar’s eighth abdominal segment are usually visible.


Avoid using harmful pesticides or practices that would carelessly destroy beneficial insects, your first line of natural defense.

Release trichogramma wasps to parasitize any newly laid eggs.

Use fast-acting organic insecticides if pest levels become intolerable.


Cucumber Beetle


Common cucumber beetles can be spotted or striped. Spotted varieties have twelve black spots on their greenish-yellow wing coverings. Striped types have black heads and three black stripes that run down their yellow-orange wing covers. Both types grow to be only 1/4 inch long.


Monitor plants and growing areas, including the growing medium, for any signs of pests.

Use baited traps early in the season where cucumber beetles are known to be a problem.

Manually remove any visible egg clusters or adults and dispose of them.


Mexican Bean Beetle

Mexican bean beetles are small, measuring about 14 inches long, with sixteen black spots on their tan yellow bodies. As they age, their bodies turn from bright yellow to orange-yellow.

Check the underside of leaves for eggs and pupal stage larvae, especially from early spring to June.

Select and destroy larvae and beetles by hand.

If an insecticide is needed, contact your local cooperative extension office for a list of approved pesticides and insecticides.


Soybean aphid

Pear-shaped bodies (1/16-inch long).

At the end of the abdomen, there are black cornicles (also known as "tailpipes").

Mouthparts for piercing and sucking are tucked under the head.

On soybean, both winged and wingless morphs are possible.

Foliar insecticides at labelled rates can be used to control soybean aphids.


Aphid resistant soybean varieties can be effective.


Soybean Diseases: Symptoms & Treatments

Fungal Disease

1. Rhizoctonia stem rot (Rhizoctonia solani)


  • Damping-off (pre- or post-emergence death) of seedlings caused by reddish-brown lesions girdling the stem

  • Lesions or cankers on the stems of older plants can cause the plant to die in the middle of the season.


  • Prior to planting, apply an appropriate fungicide to the seeds.

  • Soybean varieties with lower susceptibility should be planted.

  • Only plant in well-draining soils

2. Rust (Phakopsora pachyrhizi)


  • Water-soaked grey or red-brown spots on leaves that turn tan to dark reddish-brown lesions may also be present on stems, petioles, and pods.

  • Within the lesions, volcano-shaped uredinia (spore-producing structures) are present; plants drop leaves and mature prematurely.


  • Rust-resistant soybean varieties should be planted.

  • Foliar fungicide applications that are appropriate for the disease can aid in disease control.

Bacterial Diseases

Bacterial Blight


  • Late-season symptoms include the formation of angular lesions that range in size from small yellow to brown leaf spots.

  • Spots first appear in the mid to upper canopy.

  • Spot centres dry out and turn dark reddish-brown to black.

  • The tissue surrounding the spots appears wet and develops a yellowish-green halo.

  • Lesions that have dried out fall from the leaf.

  • The seeds can become shrivelled and discoloured.


  • Consider planting soybean products with higher ratings for resistance or tolerance.

  • Fungicides containing copper may provide control if applied early in the disease cycle.


Caused by the fungus Colletotrichum truncatum.


  • Lesions on the stem, pods, and petioles that are brown to black and irregular in shape.

  • The leaves roll and the veins between the major veins are necrotic.

  • Infected pods may be filled with mycelium rather than seeds, or the seeds may be fewer and/or smaller, as well as brown, mouldy, shrivelled, or normal in appearance.


  • Crop rotation to non-host crops is recommended.

  • Inclusion of infested residue.

  • Plant pathogen-free seed and/or treat seed with a fungicide of choice.

Disease & Pest-Resistant Seed Varieties

Resistant to Bacterial Pustules:

  • Ahilya-3

  • Alankar

  • Ankur

  • Bragg

  • Durga (JS 280)

  • Hara Soy

Resistant to Viral Diseases:

  • MACS-13

  • JS 80-21

Resistant to Yellow Mosaic:

  • Type 49

  • SL 96, SL 295

  • Shivalik

  • Improved Pelican

  • Hardee

Resistant to Bacterial Blight:

  • Ahilya-1, Ahilya-3

  • JS 79-81

Resistant to Rust:

  • EC 241778

  • EC 241780

You may visit the following sources for more information



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