Soybean Sentinel Plot Report: August 23, 2022

Summary of reports:

The reports this week indicate that most soybean fields are approaching maturity. At this point in the season, it is useful to remind folks that once soybeans reach R6 and beyond, yield is more or less set and pests have a limited influence on field. Stink bugs are an exception to this rule because they can suck moisture out of seeds, but fortunately our reports do not indicate much stink bug damage. In terms of other insect pests, grasshopper were most commonly encountered in our plots, but pest populations seem to be receding a bit. Keep in mind that once soybeans reach R4 and beyond, the economic threshold for insect defoliation is 30% defoliation across an entire field, so damage needs to be significant to justify an insecticide application that would require driving over part of the crop. For diseases, Septoria brown spot is present in most fields, as are some other diseases but populations seem to be spotty. Scout your fields to determine what is present and if populations are concerning. For information on implementing IPM in soybean fields, see our recently published fact sheet on the topic.

Background

This growing season the Pennsylvania Soybean Promotion Board is funding a Soybean Sentinel Plot Program, which is being managed by The Dept. of Entomology at Penn State and executed by Penn State Extension. In this effort, Penn State Extension Educators are regularly scouting about 25 'typical' soybean fields in about 20 counties across the state, reporting the populations of plant pathogens and insect pests that they find. Our goal is to inform the agricultural community about which pests are active across the state, so folks will have a sense of what to expect when they scout their own fields as part of an IPM program. It would be inappropriate to use these reports to justify insecticide applications.

In the reports below, pests that were found during scouting are listed with their severity, which is rated on a 1-10 scale with 10 being the highest. A severity score of 1 equates to 10% or less infestation or defoliation, a "2" aligns with 20% or less infestation or defoliation, and so on. Growers should be sure to check their own fields to determine your local populations, but these reports will indicate which pests are likely to be active in fields. Our reports are distributed via this weekly newsletter and are available via the Penn State Extension website (then search for "soybean sentinel plot").

Reports

23 August 2022 – Montgomery County – Andrew Frankenfield

Near Souderton

Growth stage: R5

• Bacterial blight – Severity: 2
• Downy mildew – Severity: 2
• No insect populations of note

22 August 2022 – Potter County – Nicole Santangelo / Jack Thomas

Two fields, one near Ulysses, one south of Ellisburg

Growth stage: R6 (Ellisburg), Ulysses (R5)

• Grasshopper – Severity: 1 (Ellisburg)
• Japanese beetle – Severity: 1
• Green stink bug – Severity: 1 (Ellisburg)
• Soybean aphid – Severity: 1 (Ulysses)
• Septoria brown spot – Severity: 1
• Deer damage present

22 August 2022 – Berks County – Sarah Frame

Near Brownsville

Growth stage: R4

• Bean leaf beetle – Severity: 1
• Grasshopper – Severity: 1
• Silver-spotted skipper – Severity: 1
• Soybean aphid – Severity: 1
• Septoria brown spot – Severity: 1
• Frogeye leaf spot – Severity: 1

22 August 2022 – Lancaster County – Jeff Graybill

Near Manheim

Growth stage: R6

• Grasshopper – Severity: 2
• Septoria brown spot – Severity: 2

19 August 2022 – Chester County – Sarah Frame

Two fields, one near South Pottstown, one near Parkesburg

Growth stage: R4

• Two-spotted spider mite – Severity: 1 (Pottstown)
• Japanese beetle – Severity: 1 (Parkesburg)
• Mexican bean beetle – Severity: 1 (Pottstown)
• Soybean aphid – Severity: 1 (Pottstown)
• Septoria brown spot – Severity: 1
• Sudden death syndrome – Severity: 1 (Pottstown)