Time to Scout for Aphids

The last couple of years we have had relatively low soybean aphid numbers. Some predictions are for high to very high numbers this year. Based on those predictions, what should you do?

Here’s my suggestion: Forget about the predictions and get out into your fields to scout, beginning now if you haven’t already. Some aphids have been found in our territory (northern Indiana, northern Ohio, and southern Michigan). I’ve not yet heard of treatment threshold levels, but it important to begin checking fields.

Aphids often show up in “hot spots”, not necessarily evenly spread across the field. Good scouting gives you a chance to find those hot spots and decide early on if treatment is warranted.

Scout by walking a circle or “z” pattern in each field. Examine the underside of leaves and the stems on five or more plants in each of five or more spots in the field. If aphids are found, make an estimate of the number per plant. Each summer I spend several minutes counting the number of aphids on a number of leaves to help me get an idea of what a given number looks like. After that annual “orientation”, I can then estimate without spending hours counting insects.

The treatment threshold is 250 aphids per plant. That threshold is very conservative – it allows at least a week before numbers will build up to truly damaging levels. In other words, if you find threshold levels, you have a week to apply treatment. My recommendation is that you plan your treatment, but rescout the field prior to actual treatment, as occasionally the insect numbers will crash and treatment will not be necessary after all.

Many growers want to treat aphids “preventatively”, i.e, throw in an insecticide with the final pass of glyphosate to “kill ‘em before they multiply”. That is not supported by science and experience. There is no justifiable reason to treat for aphids unless they have reached threshold levels in the field. This kind of treatment may also be harmful in that it kills beneficial insects which may keep the aphid numbers in check.

Please call us if we can be of assistance in scouting and/or determining the need to treat for soybean aphids.

If you have any questions or concerns please contact:

Terry Jones CPAg, Regional Agronomist @ 419.346.7786 or


or

Rod King CCA, Regional Agronomist @ 574.596.6721 or