Field Scouting: Keep On, Don’t Stop

soybean aphids

“It’s been a long year already,” said John Swanson, Federated agronomist at the Ogilvie location, but “remember to continue scouting for insects such as aphids and spider mites.”

Overall across Federated’s territory the number of insects in fields has been low, he noted, but “as we push into August, we need to monitor these insects [because] they can show up heavy and quickly.”

Spider Mites

Federated Agronomists are ready to help with spider mite identification, since they can only be seen with a hand lens. One of the more visible signs of spider mites is stippling of the leaves. “Look for this along field edges where spider mites are likely to [start and] move into fields,” said Swanson.

The UMN Extension service outlined five stages of spider mite infestation and advised spraying the “middle and upper canopy leaves to protect them” when infestations reach the third level. These are the stages as defined in the Extension article:

0: No spider mites or injury observed.

1: Minor stippling on lower leaves. No premature yellowing observed.

2: Stippling common on lower leaves. Small areas with yellowing on scattered plants.

3: Spray threshold: Heavy stippling on lower leaves with some stippling progressing into the middle canopy. Mites present in the middle canopy, with scattered colonies in the upper canopy. Lower leaf yellowing is common, and there’s some lower leaf loss.

The latter two stages, when leaf yellowing and drop become rampant, can significantly affect yield and it’s too late to spray. Read the full article here.


There have not been high numbers of aphids in Federated territory thus far but, again, “remain vigilant as number can still blow up quickly as we move through August,” said Swanson.

“Continue to scout and treat only as needed. Unnecessary treatment can be hard on the beneficials,” he said. 

To determine when to treat for aphids, the UMN Extension Service recommends that growers use “the following economic threshold through R5 (seeds developing, but pod cavity not filled). All three conditions should be true before treating.”

  • - Average of 250 aphids per plant.
  • - More than 80 percent of plants having aphids.
  • - Aphid populations increasing.

Read the full article here.

As always, your Federated Agronomist is ready to help with identifying and determining treatment thresholds for these yield-devouring pests.