Soybean Threats in Latham Country

Matt Moore

Matt Moore, Soybean Product Manager

Timely scouting is recommended to identify the presence of soybean diseases. If present, prepare a management plan for following crop years. Your management plan should include a high-quality seed treatment like Latham Seeds exclusive SoyShieldTM Plus and select varieties with natural tolerance to the disease.

Below are insects commonly spotted across Latham Country:

  • Seedcorn Maggots (SCM) are generally more of a problem when cool, moist soil conditions slow germination and early growth. Reduced tillage environments and fields with a manure application or green vegetation, such as cover crops, tend to see more problems with SCM. Flies, which are the adult stage of maggots, are attracted to decaying organic matter where they lay eggs. The maggots hatch and then burrow into soybean seed, hindering or preventing that seed from developing. Unfortunately, there are no rescue insecticide treatments available for SCM. Replanting is the only available option if stand loss is significant.
  • Wireworms feed directly on germinating soybean seeds and soybean roots, causing stand loss or uneven growth. Fields with a history of infestation and fields that were previously in pasture or CRP, are at a higher risk for wireworm. No rescue insecticide treatments are available, so management decisions must be made prior to planting. Latham’s SoyShield Plus seed treatment is an excellent control option where risk or history of either of these insect pests exist.
  • Bean Leaf Beetles (BLB) generally produce two generations annually in our geography. First-generation females deposit eggs in the soil of soybean fields. Later in the season, these eggs produce larvae that feed on soybean roots and nodules. This first generation of overwintering adults also can cause damage to emerging soybean seedlings. If damage is noted from BLB, scout the entire field to determine the average percent defoliation on affected plants and number of beetles per plant. The accepted threshold where an insecticide treatment is recommended is three to five beetles per plant from emergence through the cotyledon stage or 30% defoliation from V1 to V7.

Early-Season Soybean Disease

Several soybean disease pathogens cause damping off or root rot. These diseases can cause enough damage to prevent soybean plants from achieving their full yield potential:

  • Phytophthora can attack and rot seeds prior to emergence, causing pre- and post- emergence damping off. Phytophthora produces tan-brown, soft, rotted tissue. Infected stems appear bruised and soft, secondary roots are rotted, the leaves turn yellow, and plants frequently wilt and die at the primary leaf stage (V1).
  • Pythium can attack and rot seeds and seedlings prior to emergence. It also can cause post-emergence damping-off under wet conditions. The characteristic symptom of most Pythium infections is soft, brownish-colored, rotting tissue.

    Photo credited to the ISU Extension.

    Pythium causes symptoms similar to Phytophthora in seedlings and can only be distinguished by laboratory examination. Although Pythium causes most damage to seeds and seedlings, roots of established plants can rot and plants may be stunted.

  • Rhizoctonia can damage seeds and plants prior to or after emergence. In seedlings and older plants, a firm, rusty-brown decay or sunken lesion on the root or on the lower stem is a characteristic symptom. The infections can be superficial and cause no noticeable damage, or they can girdle the stem and stunt or kill plants.
  • Fusarium is also a common pathogen that can damage seeds and seedlings. It causes light to dark brown lesions on roots that may spread over much of the root system and may appear shrunken. Fusarium may attack the tap root and promote adventitious root growth near the soil surface and may degrade lateral roots.

SOURCE:  Soybean seed and seedling diseases | UMN Extension

Check out other articles about soybeans on The Field Position.