Plant Health Initiative

Scouting Guidelines

 

Diseases and insects show up at different, often predictable times during the growing season.

In general, scouting for insects is based on the time of the year and crop development stage, while scouting for diseases is based mainly on the crop development stage.

Disease / Pest	Growth stage to scout	Best time to scout	Best place to scout
Soybean Aphid Also look for ants and ladybird beetles.	V1-2 . Scout two times per week during this time period. Continue scouting through pod set.	In early July, start scouting to become familiar with the aphid pressure in your fields. Use a hand lens or other magnifier.	V1-2: Under young upper leaves, petioles, and stem.  Vn: new branches in the lower canopy.  R1-R4: undersides of mid-canopy leaves and stems.
Bean leaf beetle	First-generation peak in late V or early R stage. Second-generation  peak during pod-fill stage.	Early July (first generation) August (second generation).
Bean pod mottle virus	maturity	at harvest	check seed
Brown stem rot	full pod	late August	not specific
Grasshoppers	any stage	July through September	border rows near weedy or grassy areas
Green stem	maturity	at harvest
Phytophthora root or stem rot	vegetative stages	July and August	Wet and waterlogged soils. Compacted soil.
Seedling blight Pythium or Fusarium	before V2	late May or when soil temperatures are cold (<60°F)	low and wet spots
Seedling blight Phytophthora or Rhizoctonia	before V2 (late planted)	mid-June or when soil temperatures warm to 70-80°F.	low and wet spots
Soybean Cyst Nematode	6 weeks after planting up until 3 to 4 weeks before harvest.	Easier to observe  on soybean roots early in the season.	A suspect area: a field entrance, areas that had flooded, weedy areas, lower yielding areas.
Soybean mosaic virus	maturity	at harvest	check seed
Spider Mites	any stage	July and August, especially during periods of drought	plants near the edges of the fields or where soybeans are stressed
Stem borer	late V, early R	mid-summer	Individual wilted or dying leaves in the middle of the canopy. Later in the season, look for lodged plants.
Sudden death syndrome	pod setting	after mid-August	high-moisture areas in fertile fields
White mold mushroom (apothecia)	at canopy closure	last week of June, 1st week of July, varies with row spacing	high soil moisture areas, especially during flowering. Areas where moisture collects due to fogs, extended dew periods and pockets of poor air drainage.
White-mold- infested plants	pod setting	August-September	visibly dead plants
Soybean viruses	maturity	at harvest	check seed

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Resources

Plan your disease scouting
X.B. Yang, Iowa State University

Estimating soybean defoliation - Iowa State University

Diagnosing Soybean Diseases in the Field - University of Wisconsin