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Soybean Sentinel Plot Report for August 20, 2019

By John Tooker
 
Summary of reports from around Pennsylvania:
 
Most of the fields that we are scouting are in later reproductive stages and the opportunity for insects to influence yield is decreasing. Defoliation in some of these fields is reaching 15%, which is the economic threshold for this type of damage. However, once plants reach growth stage R5-R6, defoliation appears to have a limited effect on plant productivity, and you might experience a greater yield loss from driving a sprayer through the soybean field than from the defoliation. Our reports indicate that Japanese beetles, grasshoppers, and bean leaf beetles are most widely reported. Some fields also have growing populations of soybean aphid. Soybean aphids do not tend to influence yield after R5.5-R6, so scout those populations to know how many aphids are on your plants and do not assume you need insecticide to stop aphid populations. In many cases lady beetles are coming to the rescue. Give these predators, and others (Figure 1), a chance to help by avoiding insecticide application unless you are certain your aphid populations are above threshold and you are a few weeks away from R5-R6.
 
As for diseases, frogeye leaf spot and Septoria brown spot are widely reported, but populations do not appear to be worth treating. Happy socuting!
 
 
Figure 1: This time of year, predator populations can be common in soybean fields. Predators, like this predaceous stink bug killing a caterpillar, help control pest populations.
 
Background on the project:
 
For eighth consecutive 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 30 or so ‘typical’ soybean fields in twenty-three counties across the state, reporting the populations of plant pathogens and insect pests that they find. Our goal is to inform the agricultural community 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
 
20 August 2019 – Montgomery County – Andrew Frankenfield
Growth stage: R5
  • Minor insect populations
  • Frogeye leaf spot – Severity: 1
  • Septoria brown spot – Severity: 1
20 August 2019 – Crawford County – Joel Hunter
Growth stage: R5
  • Grasshoppers – Severity: 1
  • Frogeye leaf spot – Severity: 1
  • Septoria brown spot – Severity: 1
20 August 2019 – York County – Heidi Reed
Growth stage: R5
  • Japanese beetle – Severity: 1
  • Bean leaf beetle – Severity: 2
  • Frogeye leaf spot – Severity: 1
  • Soybean brown spot – Severity: 1
20 August 2019 – Schuylkill County – Dwane Miller
Growth stage: R5
  • Japanese beetle – Severity: 1
  • Green cloverworm – Severity: 1
  • Grasshoppers – Severity: 3
  • Bean leaf beetle – Severity: 2
  • Silver-spotted skipper – Severity: 1
  • No diseases noted
19 August 2019 – Bedford County – Zach Larson
Near Cessna
Growth stage: R6
  • Bean leaf beetle – Severity: 1
  • Japanese beetle – Severity: 1
  • Green cloverworm – Severity: 1
  • Septoria brown spot – Severity: 1
  • Frogeye leaf spot – Severity: 1
19 August 2019 – Cambria County – Zach Larson
Near Loretto
Growth stage: R5
  • Bean leaf beetle – Severity: 1
  • Japanese beetle – Severity: 1
  • Green cloverworm – Severity: 1
  • Septoria brown spot – Severity: 1
  • Frogeye leaf spot – Severity: 1
19 August 2019 – Northumberland County – Anna Busch
Growth stage: R6
  • Japanese beetle – Severity: 1
  • Soybean aphid – Severity: 1
  • Bean leaf beetle – Severity: 1
  • Grasshopper – Severity: 1
  • Green cloverworm – Severity: 1
  • Frogeye leaf spot – Severity: 1
  • Septoria brown spot – Severity: 1
19 August 2019 – Union County – Anna Busch
Growth stage: R6
  • Soybean aphid – Severity: 1
  • Bean leaf beetle – Severity: 2
  • Grasshopper – Severity: 1
  • Thrips – Severity: 1
  • Beneficial insects: lady beetles
  • Frogeye leaf spot – Severity: 1
  • Septoria brown spot – Severity: 1
19 August 2019 – Bradford County – Casey Guindon
Growth stage: R5
  • Japanese beetle – Severity: 1
  • Unidentified defoliation – Severity: 1
  • Frogeye leaf spot – Severity: 1
18 August 2019 – Potter County – Jack Thomas and Nicole Carutis
Near Ellisburg
Growth stage: R4
  • Japanese beetle – Severity: 1
  • Grasshoppers – Severity: 1
  • Beneficial insects: Lady beetles
  • Frogeye leaf spot – Severity: 2
  • Septoria brown spot – Severity: 1
18 August 2019 – Potter County – Jack Thomas and Nicole Carutis
South of Galeton
Growth stage: R5
  • Japanese beetle – Severity: 2
  • Grasshoppers – Severity: 1
  • Beneficial insects: Lady beetles
  • Septoria brown spot – Severity: 1
18 August 2019 – McKean County – Jack Thomas and Nicole Carutis
Growth stage: R3
  • Japanese beetle – Severity: 1
  • Grasshoppers – Severity: 1
  • Beneficial insects: Lady beetles and bumble
  • Septoria brown spot – Severity: 1
15 August 2019 – Centre County – Adrian Murillo-Williams
Growth stage: R5
  • Bean leaf beetle – Severity: 2
  • Grasshoppers – Severity: 2
  • Japanese beetle – Severity: 1
  • Soybean aphid – Severity: 1
  • Beneficial insects: Lady beetles
  • Soybean downy mildew – Severity: 1
  • Frogeye leaf spot – Severity: 2
12 August 2019 – Bradford County – Casey Guindon
Growth stage: R4
  • Japanese beetle – Severity: 1
  • Soybean aphid – Severity: 1
  • Beneficial insects: Lady beetles
  • Frogeye leaf spot – Severity: 1

Source : psu.edu