Stem borers lay their eggs on the leaves or stems of the plants, and once the larvae hatch, they tunnel into the stem, feeding on the plant tissues. This feeding activity weakens the stems, making them more susceptible to lodging and breakage. Stem borers can also introduce secondary infections, such as fungal diseases, further exacerbating the damage.

While stem borers can infest soybeans at various stages of their growth, they are most commonly found in the early to mid-season stages. It is during this critical period that the pests lay their eggs on soybean plant leaves or stems. After hatching, tiny larvae bore into the stems, where they feed and develop, causing significant crop damage.

Identifying stem borers in soybeans can be a difficult task, as these pests tend to spend the majority of their lifecycle hidden inside the stems of the plants. However, there are several key indicators that can help to identify their presence.

1. Entry Points and Frass: Pay close attention to the stems of soybean plants and look for small holes or entry points, which are often accompanied by the presence of frass or sawdust-like material. These signs can be a strong indication of a stem borer infestation.

2. Wilting and Yellowing: Be on the lookout for any wilting or yellowing of the leaves, as well as stunted plant growth. These symptoms can be attributed to the damage caused by stem borers, as they disrupt the normal flow of nutrients and water within the plant.

3. Susceptibility to Breakage: Watch for the susceptibility of the plants to break easily at the base, which can be a result of the weakening of the stem caused by stem borer feeding activity.

4. Adult Moths: The presence of adult moths flying around the field, especially during the evening hours, indicate the potential threat of stem borers.

5. Neighboring Fields: Observe neighboring fields with infestations. If nearby fields are struggling with stem borers, be vigilant and take proactive, preventive measures to protect your fields.

Stem borers are a common pest in soybean-growing regions worldwide, but they are particularly prevalent in areas with warm climates and high humidity. Regions such as the southern United States, South America, Africa, and parts of Asia are especially susceptible to infestations.

To effectively manage stem borers, it is crucial to implement proactive measures. Cultural practices can help reduce the risk of infestation. These practices include:

• crop rotation

• intercropping

• maintaining proper plant spacing

Regular field scouting is essential to detect early signs of infestation, such as wilting or entry holes in the stems. If any infested plants are observed, it is recommended to remove and destroy them to prevent the spread of the pests.

When deciding whether to employ chemical products to control stem borers in soybeans, farmers should first assess the severity of the infestation and determine the economic threshold for treatment. Once fields have reached a level of infestation at which chemical products are needed, consider integrating other management practices alongside chemical control, such as crop rotation, biological control, and pheromone traps, to enhance effectiveness and reduce reliance on insecticides. Rotating between different modes of action helps prevent the development of resistance in stem borer populations, ensuring long-term sustainable pest management.

Foliar applications to manage adult beetles generally require several applications due to extended emergence over many weeks. In the larval stage, the insect is protected inside the plant stem so it is less susceptible to topical insecticide treatments.

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