Soybeans: Put a Hold on Pest-Management Costs – Follow Economic Thresholds

    As the summer light falls on your growing soybean fields, you might wish you had X-ray vision to determine your levels of pests. You might also wish you had crystal ball to tell you when to act.

    Luckily, you don’t need special powers. You have economic thresholds.

    Researchers develop economic thresholds to help farmers determine when treatments will bring a monetary benefit. An economic threshold is the point at which you need to take action to prevent a yield-limiting problem – insects or diseases – from exceeding the cost of control.

    There’s a threshold for that

    Although different types of pests require different types of treatments, the first question to ask is the same: Does the pest population meet the economic threshold?

    “The economic threshold is also known as the ‘action threshold,’ since this is when farmers should begin to act against the insect or disease,” says Angus Catchot, Ph.D., Mississippi State University Extension entomology professor.

    An economic threshold is designed to help farmers know when to invest in management of an insect, disease or other pest to keep it from reaching the economic injury level (EIL).

    The EIL, which depends on several factors including crop values and management costs, is when the crop value lost to plant injury caused by the pest exceeds the cost of the treatment.

    Since crops can tolerate some level of damage with no impact on yield, treatment at the economic threshold is the most cost-effective management approach and might also result in the highest yields.

    “In nearly every situation, yield will be protected by applying appropriate treatment targeted at the pest of interest when economic thresholds are reached,” says Catchot.

    He cautions farmers to avoid treating their fields automatically.

    “Insecticides applied when no or very few pests are present often causes the farmer to spend money that does not provide an economic return,” says Catchot. “Plus, that treatment might increase other insect pests by killing beneficial insects.”

    Unwarranted applications could also potentially increase insect resistance to the insecticide.

    Herbicide Resistance Info

    Scouting matters

    Farmers must put their scouting skills to work when evaluating their fields.

    No matter your pest problem, walking your fields to check its status is the first step.

    You’ll likely see some level of crop injury while scouting, but thresholds help you decide if you need to do something about it. Thresholds are the point at which you lose more in yield than the cost of inputs to save your crop.

    3 steps for putting thresholds to use

    • Only apply treatment after thresholds are met: Applying treatment before thresholds are met can sharply decrease profitability because your costly input might not bring a big enough yield return to justify it.
    • Apply effective treatment: Many types of treatments exist to control insects, weeds and diseases – but not all treatments are effective for all insects and diseases. Check product labels and consult your product retailer to ensure you’re using the most effective treatment for your biggest yield-limiting pest.
    • Know your enemies: Each insect and disease has unique characteristics and targets different areas of the soybean plant. Know what to look for and where.

    For the most up-to-date threshold information in your area, contact your state or local extension office.

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