Battle for the Belt: Season 3, Episode 15 - Scouting and Management of Soybean Insects

Season 3, Episode 15 of Battle for the Belt is now available: https://youtu.be/lHtE8krmtAo?si=PAbILS3BdBQzCAUA  

At this time of year, with rapid crop growth, soybean crop management should prioritize monitoring for foliar insect pests. Focus scouting efforts on defoliators such as various caterpillar species and grasshoppers, the latter being more prevalent under dry conditions. July typically marks the highest period for defoliation, making regular field scouting essential. When assessing damage, it is important to evaluate the overall field for defoliation, not just field borders. Thresholds for management differ by growth stage (Figure 1):

• From vegetative to bloom (V1-R2), insecticide applications are recommended when defoliation reaches 30%
• From pod development to full seed (R3-R6), the threshold drops to 10–15%, provided the insects remain actively present in the field.  

A unique challenge this season involves late planted and late maturing soybean plants, which may result in green, actively growing fields persisting longer than usual this fall. As early planted fields begin to dry down, insect pests are likely to migrate toward these greener areas, creating concentrated pest populations. Notably, bean leaf beetles (Figure 2) have shown increased activity in these late-maturing varieties, and stink bugs (Figure 3) are expected to move from senescing fields into those still in vegetative or early reproductive stages. This shifting pressure underscores the need for heightened vigilance in late-planted fields.

Effective pest management requires a field-wide evaluation to both estimate the extent of defoliation and correctly identify the pest species responsible for any damage present, as threshold levels vary depending on the insect. Accurate diagnosis is critical to determining the appropriate treatment strategies. For additional guidance on insect identification and defoliation thresholds, consult the Soybean Defoliation Guide, available at: aginsects.osu.edu.

Crop Progress Updates from the Field 

Across the state, corn and soybean entered reproductive stages last week. Rain is important during this time to reduce heat stress to ensure complete pollination in corn. While rainfall is also important to soybean plants currently, they are most susceptible to drought stress later in the season during, grain fill.

The Western location had a few plants with tassels but most of planting date one (4/18) corn was about V14 (Figure 4). The rest of the planting dates are still in young vegetative stages. In soybean, the first two planting dates (4/18, 5/12) are flowering, with the first planting date getting close to R3.

The Wooster location is the furthest behind in corn growth with the first planting date (3/27) only at V10. However, the first two planting dates of soybean are at R2. The rest of the planting dates are in early vegetative stages.

At the Northwest location, planting date one (3/27) in corn is at V12, with the later planting dates at early vegetative stages. The first two planting dates of soybean are at R2 (3/27, 4/17), while the later planting dates are in early vegetative growth (Figure 5).

Thus far in the growing season, there has been minimal insect feeding/defoliation in corn and soybean at all three locations. Disease symptoms have also been absent in our field, but it is important to be scouting as we move into reproductive stages, especially with these hot temperatures and frequent rain events.

Follow the Battle for the Belt campaign all season long to stay informed and up to date. Catch every episode on the Ohio State Agronomy YouTube channel. Ohio State Agronomy