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Soybean Aphids: What You Need to Know

Aug 22, 2019

Agronomy, Crop Management, Grain, Soybean, Technology

A wet spring and early summer have helped to keep soybean aphids at bay this growing season. However, as we head into August and begin to see temperatures decrease during the day, soybean aphid pressure may increase.close up of soybean aphids on crop

The optimal reproduction and development environment for any of the aphid’s 15+ generations, is between 70 and 80 degrees Fahrenheit. During optimal conditions, soybean aphid populations can grow rapidly, in as little as 2 to 3 days, creating both a nuisance and yield burden this growing season and into the 2020 growing season, as well.

To help our producers stay ahead of the potential onslaught, our Arthur Companies agronomists have put together a quick checklist of what to look for and dos and don’ts.

  1. Know your enemy

Soybean aphids only utilize two plants to complete their lifecycle: common buckthorn and soybean. The aphids use the leaves of the buckthorn plant to lay their eggs and overwinter; eggs will survive in temperatures as low as -29F. Don’t rely on a cold winter to mitigate your infestation risk the following summer.

Wingless generations will be produced on the buckthorn plant each spring before a winged aphid is produced and migrates to the soybean plant. Many generations will be produced in the soybean field without mating. The final generations return to the buckthorn plants to lay eggs and perpetuate the cycle into the next production year. An effective IPM will recognize the importance of buckthorn control, as well as in-field control of the pest.

  1. Scout for effective IPM

Scouting is the most important component of your integrated pest management plan—you can’t control what you don’t know is there! And since low population densities of soybean aphids have already been detected in the state, producers should be actively scouting their soybean fields.

agronomist scouting soybean crop

For adequate field condition representation, scout fields in a V or W pattern, sampling 38 plants per 50 acres of soybeans. Start a plant inspection by looking at the bottom portion first, estimating the number of aphids per leaf as you work your way up the plant, since aphids will often concentrate on the upper leaves of the plant.

Estimate the number of aphids per soybean leaf, only counting the small yellow aphids (both winged and non-winged) with black cornicles. White cast skins will also be present on the soybean leaves but should not be counted in the establishment of economic threshold.

Both identifying the presence of aphids and their excreted waste, also known as honeydew, will confirm infestation. Yield threshold is estimated at 250 aphids per plant in 80% of the plants in the field with evidence of populations increasing.

  1. React and don’t skimp on treatment

Few situations call for a reactive, rather than a proactive, approach; soybean aphid control is one. Actively monitor populations keeping in mind that populations can double every 36 to 48 hours, and don’t rush to treat your fields with insecticide.

close up of agronomist scouting soybean crop

Here’s why:

  • Amassed research shows that there is no negative yield impact when population is below 250 aphids per leaf.
  • Lady beetles and syrphid flies are natural predators of the soybean aphid and are also susceptible to the same insecticides that kill them. Save yourself some time and money—and potential resistance issues—and let the predators control soybean aphids when population is under threshold. Killing all of the insects on the plants, both pest and beneficial, can open fields to spider mite infestation.
  • Chemicals aren’t cheap and neither is your time. Don’t needlessly spray and don’t apply less chemical than the directed dosage prescribes.
  • Typically, a second insecticide application will be warranted when an initial treatment is applied prior to reaching the 250 aphid per leaf economic threshold.

Insect damage can devastate your yields, but you have options, and your Arthur Companies team is only a phone call away. Our agronomists can help answer any questions you may have about when to scout, what to look for and treatment options available, and, as always, we look forward to hearing from you.