Soybeans: Top Three Insect-Scouting Tips to Minimize Yield Loss

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    If an insect lands on a soybean plant but there’s no one there to hear it, does it make a sound?

    As you contemplate the answer to that question, think about how many bugs might be buzzing through your soybean fields right now. They may be decreasing your yields, and you don’t even know it.

    “Our biggest shortcoming with pest management isn’t what we spray or understanding thresholds,” says Scott Stewart, Ph.D., the integrated pest management specialist at the University of Tennessee. “It’s knowing what is out in the field.”

    Stewart and other researchers agree that scouting is one of the most effective management practices to minimize yield loss from pests. Yet, too often, farmers don’t utilize the practice.

    “The most important thing that farmers can put on their fields is their shadow,” says Mo Way Ph.D., an entomology professor at Texas A&M University.

    Below, Way and Stewart weigh in on three best management practices that they recommend for effective insect scouting:

    Scout early, scout often

    Regular scouting and documentation of pests helps farmers know what’s happening in their fields, determine if economic thresholds have been reached and decide whether to apply treatment. Scouting also helps detect non-insect related problems like weed issues, disease and nutrient deficiencies.

    “Scouting activities should be performed at least weekly, especially during critical times,” says Stewart. “Farmers should pay special attention to scouting their fields the first two weeks after planting and from the full-bloom (R2) through full-seed (R6) growth stages when soybeans are the most susceptible to pest damage.”

    Way agrees that fields should be scouted weekly and suggests that farmers scout in several areas of their fields, not just the edges.

    “Farmers should visually inspect the edges, middle and corners of their fields,” he says. “Walking through the field diagonally will give farmers a good idea of any problems they may be encountering.”

    Look for changes

    Only through regular scouting can farmers monitor changes in field conditions and treat problems effectively. Farmers should monitor their fields for stand loss, defoliation and significant changes in insect density, which can signal the need for field treatment.

    “Some fields may be clean and won’t need to be checked as often,” says Stewart. “But others may need to be monitored more often as insects appear and thresholds are reached.”

    As insect populations grow, Way reminds farmers that insects should not be treated until thresholds are reached.

    “A soybean field is like an insectary and is full of both pests and beneficial insects,” he says. “By scouting, a farmer can delay pesticide applications and preserve the number of beneficial insects while reducing the pesticide load on the environment.”

    Use the proper tools

    While visual checks are beneficial early in the growing season, researchers suggest using a sweep net or drop cloth once soybeans have matured to accurately determine insect population estimates.

    “Once soybeans reach between knee and waist high farmers should begin using a sweep net during scouting,” Way says. “I recommend that farmers use semicircular sweeps; they should consecutively sweep in a figure-eight pattern while walking down the row.”

    For more information on sweep nets, thresholds and other insect management information, consult your local extension agent.

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